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I 


QUAIN  AND  SHARPEY’S 


QUAIN’S  ANATOMY. 


VOL.  II. 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/humananatomy21quai 


* 


MAN 

ANATOMY 

BY 

JONES  QUAIN,  M.D. 

EDITED  BY 

RICHARD  QUAIN,  F.R.S. 

AND 

WILLIAM  SHARPLY,  M.D.  F.R.S. 

PROFESSOES  OP  ANATOMY  AND  PHYSTOLOGY,  IN  DNIVEESITY  COLLEGE,  LONDON. 

FIRST  AMERICAN,  FROM  THE  FIFTH  LONDON  EDITION, 

EDITED  BY 

JOSEPH  LEIDY,  M.D. 

IN  TWO  VOLUMES. 

V7ITH  OVEH  FIVE  HUNDRED  ILLUSTRATIONS. 

VOL.  II. 


PHILADELPHIA: 

LEA  AND  BLANCHARD. 
1849. 


Entered,  according  to  Act  of  Congress,  in  the  year  1849, 

BY  LEA  AND  BLANCHARD, 

In  the  Clerk’s  Office  of  the  District  Court  for  the  Eastern  District  of  Pennsylvania. 


phiiadelphia: 


C.  SHERMAN,  PKINTEK, 
19  St.  James  Street. 


CONTENTS  OF  THE  SECOND  VOLUME 


VEINS  ------ 

The  Veins  of  the  Head,  Face, 
and  Neck  - - - - 

Facial  Veins  - - - 

Temporal  Veins 
External  Jugular  Vein 
Internal  Jugular  Vein 
The  Veins  of  the  Upper  Limb  - 
Axillary  Vein  - - - 

Subclavian  Vein 
Innominate  Vein 

The  Upper  Vena  Cava  - - - 

The  Azygos  Vein  - - - 

The  Veins  of  the  Spine  and 
Cranium  - - - - 

The  Cerebral  Veins  - - - 

The  Cranial  Sinuses 
The  Ophthalmic  Vein 
The  Veins  of  the  Diploe  - 

The  Veins  which  form  the  Lower 
Vena  Cava  - - - - 

The  Femoral  Vein  - - - 

The  External  Iliac  Vein  - 
The  Internal  Iliac  Vein  - 

The  Common  Iliac  Vein  - 

The  Lower  Vena  Cava  - - - 

The  Portal  system  of  Veins 
The  Veins  of  the  Heart  - 

LYMPHATIC  SYSTEM  - 

Lymph  - - - - - 

Chyle  - - - - - 

Lymphatic  Vessels  - - - 

ABSORBENTS  - - - - 

The  Thoracic  Duct  - - - 

The  Right  Lymphatic  Duct 
The  Lymphatics  of  the  Lower 
Limb  - - - - - 

The  Lymphatics  of  the  Abdomen 
and  Pelvis  - - - - 

The  Lymphatics  of  the  Thorax 


Absorbents — continued.  page 

The  Lymphatics  of  the  Upper 
Limb  -----  56 

The  Lymphatics  of  the  Head 
and  Neck  - - - - 67 

EPIDERMIC,  EPITHELIAL,  or  CU- 

TICULAR  Tissue  - - - 59 

PIGMENT 69 

ADIPOSE  Tissue  - - - - 71 

SEROUS  Membranes  - - - 75 

MUCOUS  Membranes  - - - 78 

THE  SKIN 84 

SECRETING  Glands  - - - 97 

ORGANS  OF  RESPIRATION  - 105 

The  Trachea  and  Bronchi  - 105 

The  Pleurae  - - - - 109 

The  Lungs  - - - - HQ 

Development  of  the  Lungs  and 
Trachea  - - - - 122 

The  Larynx  - - - - 123 

The  Thyroid  Body  - - - 140 

The  Thymus  Body  - - - 142 

NEUROLOGY  - - - - 146 

NERVOUS  SYSTEM  - - - 146 

Cerebbo-Spinal  Axis  - - - 184 


Weight  of  different  parts  - - 184 

Spinal  Cord  - - - - 190 

Encephalon  - - - - 195 

Medulla  Oblongata  - - 197 

Pons  Varolii  - - - 201 

Cerebrum  - - - - 202 

Cerebellum  - - - 224 

Internal  structure  of  Cerebro- 
spinal Axis  - - - - 229 

Connexions  of  Cranial  Nerves  - 242 

Membranes  of  Brain  and  Spinal 
Cord 247 


PAGE 

6 

6 

6 

8 

9 

10 

11 

14 

14 

16 

16 

17 

18 

21 

21 

24 

24 

26 

26 

27 

27 

27 

28 

29 

30 

33 

33 

35 

37 

44 

46 

47 

47 

60 

54 


VI 


CONTENTS. 


Ckrebro-Spinal  Axis — continued. 
Development  of  Brain  and  Spinal 
Cord  - - - - - 

Cranial  Nerves  in  general  - 

Olfactory  - . . . 

Optic  - - - - - 

Third  Pair  . - - - 

Fourth  Pair  - - - - 

Fifth  Pair  . . - . 

A.  Ophthalmic  Nerve 

B.  Upper  Maxillary  Nerve 

C.  Lower  Maxillary  Nerve 

Sixth  Pair  - - . - 

Seventh  Pair  - - - - 

A.  Facial  Nerve 

B.  Auditory  Nerve  - 

Eighth  Pair  _ - - - 

A.  Glosso-pharyngeal 

B.  Pneumogastric 

C.  Spinal  Accessory  - 

Ninth  Pair  - . . - 

Spinal  Nerves  in  general 

The  Posterior  Divisions  of  Spinal 
Nerves-  . - - - 

of  Cervical  Nerves  - 
of  Dorsal  Nerves 
of  Lumbar  Nerves 
of  Sacral  Nerves 
of  Coccygeal  Nerves  - 
The  Anterior  Divisions  of  Spinal 
Nerves  ----- 
of  first  four  Cervical  Nerves 
The  Cervical  Plexus  - 
of  last  four  Cervical  Nerves 
The  Brachial  Plexus  - 
Branches  of 
of  Dorsal  Nerves 
of  Lumbar  Nerves 

The  Lumbar  Plexus  - 
Branches  of 

of  Sacral  and  Coccygeal 
Nerves  - - - - 

The  Sacral  Plexus 
Branches  of 

Sympathetic  Nerve  in  general 
The  Gangliated  Cords  of  Sympa- 
thetic N erve - - - - 

Cervical  portion  of  - 
Thoracic  portion  of  - 
Lumbar  portion  of  - 
Sacral  portion  of  - - 

The  Prevertebral  part  of  Sym- 
pathetic Nerve  - - - 

The  Cardiac  Plexus  - - - 

The  Epigastric  or  Solar  Plexus 
The  Diaphragmatic  Plexus 
The  Supra-renal  Plexus 
The  Renal  Plexus 
The  Spermatic  Plexus 
The  Caeliac  Plexus,  and  its 
Divisions  - . . 

The  Superior  Mesenteric 
Plexus  - - - - 


Sympathetic  Nerve — continued.  page 
The  Aortic  Plexus  - - 353 

The  Inferior  Mesenteric 
Plexus  - - - - 353 

The  Hypogastric  Plexus  - - 354 

The  Inferior  Hypogastric 
Plexus  - - - - 354 

The  Haemorrhoidal  Nerves  354 
The  Vesical  Plexus  - - 355 

The  Prostatic  Plexus  - 355 

The  Nerves  of  the  Ovary  - 355 
The  Vaginal  Plexus  - - 356 

The  Nerves  of  the  Uterus  - 356 

ORGANS  OF  THE  SENSES  - - 358 

The  Eye  -----  353 
The  Appendages  of  the  Eye  - 358 
The  Globe  of  the  Eye  - - 362 

The  Ear 373 

The  External  Ear  - - - 373 

The  Middle  Ear  or  Tympanum  377 
The  Internal  Ear  or  Labyrinth  386 

The  Nose  -----  396 

Nasal  Fossse  - - - - 399 

ORGANS  OF  DIGESTION  - - 404 

The  Mouth  - - - - 404 

The  Teeth  . - - - 405 

The  Tongue  - - - - 429 

The  Palate  - - - - 434 

The  Tonsils  - - - - 436 

The  Salivary  Glands  - - 437 

The  Pharynx  - - - - 440 

The  Q5sophagus  - - . 442 

The  Abdomen  - - - - 443 

The  Stomach  - - - - 446 

The  Small  Intestine  - - - 453 

The  Duodenum  - - - 459 

The  Jejunum  and  Ileum  - 461 
The  Large  Intestine  - - 462 

The  C*cum  - . - 464 

The  Colon  - - - 466 

The  Rectum  - - - 467 

The  Anus  and  its  Muscles  - 469 

Development  of  the  Alimentary 
Canal  -----  472 
The  Liver  - - - - 474 

The  Excretory  Apparatus  of  488 
Development  and  Fcetal 

Peculiarities  of  - - 491 

The  Pancreas  - - - - 493 

The  Spleen  - - . - 496 

The  Peritoneum  - - - 600 

Parts  situated  in  each  region  of 
the  Abdomen  - - - 505 

THE  URINARY  ORGANS  - - 506 

The  Kidneys  - - - - 506 

The  Supra-renal  Capsules  - 514 

The  Ureters  - - - - 516 

The  Urinary  Bladder  - - 517 

The  Urethra  - - - - 524 


PAGE 

253 

259 

260 

260 

261 

262 

263 

264 

268 

273 

278 

278 

279 

282 

283 

283 

285 

292 

292 

294 

297 

297 

299 

300 

300 

301 

301 

301 

302 

306 

306 

306 

317 

320 

321 

321 

329 

330 

330 

339 

341 

341 

345 

347 

348 

348 

348 

350 

351 

351 

351 

351 

352 

352 


CONTENTS. 


vii 


PAGE 

Organs  of  Generation — continued. 

PAGE 

ORGANS  OF  GENERATION - 

- 

526 

The  Ovaries  and  Fallopian  Tubes 

564 

Of  the  Male  - - - - 

- 

526 

Development  of  the  Genito-Uri- 

The  Prostate  Gland  - 

- 

526 

NART  Organs  - - - - 

567 

The  Penis  - . - 

- 

528 

The  Urethra  - - - 

- 

534 

The  Mammary  Glands  - - - 

574 

The  Muscles  of  the  Penis  and 

Urethra  . - - 

- 

537 

SURGICAL  ANATOMY  - 

577 

The  Testis  and  Spermatic  Cord 

540 

The  Parts  concerned  in  Inguinal 

The  Coverings  of  - 

- 

540 

Herniae  - - - . 

578 

The  Testes  - - - 

- 

545 

Inguinal  Hernise 

584 

The  Vas  Deferens  - 

- 

549 

The  Parts  concerned  in  Femoral 

The  Vesiculoe  Seminales 

and 

Herma  - - - - 

591 

Ejaculatory  Ducts 

- 

551 

Femoral  Herniae 

595 

Of  the  Female  - - . 

- 

554 

The  Perineum  and  Ischio-Rectal 

The  Vulva  ... 

- 

654 

Region  - - - - - 

598 

The  Vagina  - - - 

- 

557 

Lateral  operation  of  Litho- 

The Uterus  - - . 

- 

659 

tomy  - - - - 

604 

INDEX 


608 


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ELEMENTS  OF  ANATOMY. 


VEINS. 

The  veins  are  those  vessels  through  which  the  blood  returns  from 
the  capillaries  to  the  heart.  They  admit  of  being  arranged  into  two 
distinct  classes ; viz.,  the  systemic  veins,  which  convey  the  dark  or 
effete  blood  from  all  parts  of  the  body  back  to  the  right  auricle  of  the 
heart ; and  the  pulmonary  veins,  by  which  the  reoxygenated  or  red 
blood  is  carried  from  the  lungs  to  the  left  auricle  of  that  organ. 

The  pulmonary  veins,  a distinct  set  of  vessels  from  the  bronchial 
veins  or  veins  concerned  in  the  nutrition  of  the  lungs,  serve  a special 
use  connected  with  respiration,  and  will  be  described  with  the  anatomy 
of  the  respiratory  organs. 

The  systemic  veins,  which  are  now  to  be  considered,  commence  in 
the  capillary  vessels  of  all  parts  of  the  body  by  means  of  small  branches, 
which,  uniting  into  fewer  and  larger  branches,  and  anastomosing  freely 
with  each  other,  end  for  the  most  part  in  two  large  venous  trunks — 
the  upper  and  lower  vense  cavse — which  empty  their  contents  into  the 
right  auricle  of  the  heart.  The  veins  from  the  walls  of  the  heart  itself 
open  at  once  into  the  cavity  of  the  right  auricle. 

There  is,  however,  one  set  of  systemic  veins  (those  of  the  chylopoietic 
viscera,)  the  large  branches  of  which  do  not  tend  directly  to  the  heart 
or  to  one  of  its  great  veins.  Thus,  the  veins  of  the  stomach,  intestines, 
pancreas,  and  spleen  unite  into  a single  large  trunk,  which  again 
branches  out  in  the  manner  of  an  artery  within  the  liver,  and  ends  in 
a capillary  system  in  the  substance  of  that  gland.  This  large  venous 
trunk  is  Xhe  portal  vein  (vena  portae) ; and  the  branches  of  which  it  is 
composed,  with  those  into  which  it  divides  within  the  liver,  constitute 
the  portal  system  of  veins. 

Other  veins,  named  hepatic,  commencing  in  the  capillaries  of  the 
liver,  and  resembling  in  their  arrangement  the  systemic  veins  generally, 
convey  the  blood  to  the  lower  vena  cava,  and  thence  to  the  heart. 

The  veins  of  many  parts  of  the  body  consist  of  a subcutaneous  and 
a deep  set,  which  have  very  frequent  communications  one  with  the 
other.  In  some  parts  of  the  body,  to  be  mentioned  particularly  here- 
after, the  veins  are  provided  with  valves,  whilst  in  others  no  valves 
exist. 

[In  some  positions  the  veins  are  so  numerous,  and  so  frequently  anas- 
tomose, as  to  form  plexuses  so  close  as  hardly  to  leave  any  appreciable 

VOL.  II.  2 


6 


FACIAL  VEIN. 


interval ; as  around  the  prostate  gland  and  neck  of  the  bladder,  the 
rectum,  interior  surface  of  the  spinal  canal,  &c.  The  deep  veins  pro- 
bably do  not  present  more  frequent  anomalies  of  distribution  than  the 
arteries,  but  the  superficial  ones  vary  their  course  more  frequently.] 

The  systemic  veins  may  be  arranged  and  described  in  certain 
groups,  according  to  their  mode  of  termination  in  the  heart. 

a.  In  the  first  group  are  included  the  various  branches  of  the  upper 
vena  cava,  viz.,  those  of  the  head,  neck,  upper  limbs,  and  walls  of  the 
thorax.  With  this  part  of  the  venous  system  the  cerebro-spinal  veins 
may  also  be  arranged ; and  the  azygos  veins  (great  and  small)  also 
belong  to  this  upper  group  of  veins,  and  serve  to  connect  it  with  the 
next  or  lower  set. 

b.  The  second  group  of  veins  consist  of  those  which  end  in  the 
lower  vena  cava.  They  are  derived  from  the  lower  limbs,  and  from 
the  lower  part  of  the  trunk — the  portal  system  being  considered  as  an 
adjunct. 

c.  Lastly,  the  veins  from  the  substance  of  the  heart  open  directly 
into  the  right  auricle,  and  are  therefore  not  connected  with  either  of 
the  sets  of  veins  ending  in  the  two  vena3  cavas. 

THE  VEINS  OF  THE  HEAD,  FACE,  AND  NEClt. 

The  veins  of  the  head  are  divided,  like  the  arteries,  into  two  sets, — 
those  which  ramify  on  its  exterior,  and  those  placed  in  its  interior. 
The  latter,  or  cerebral  veins  and  sinuses,  will  be  presently  described. 
The  veins  of  the  head  and  neck,  with  one  exception,  have  no  valves. 
The  external  jugular  vein,  the  exception  alluded  to,  is  provided  with 
a valve  at  its  entrance  into  the  subclavian  vein ; and  in  most  cases 
with  another  about  the  middle  of  its  course.  These  valves,  however, 

are  not  efficient  in  stopping 
the  regurgitation  of  the  blood, 
or  the  passage  of  injections 
from  below  upwards. 

The  veins  on  the  exterior 
of  the  head  and  face  converge 
and  unite,  so  as  to  form  two 
trunks,  the  facial  and  the  tem- 
poral veins. 

FACIAL  VEIN. 

The  facial  vein,  fig.  256,  a, 
[vena  facialis,]  lies  obliquely 
along  the  side  of  the  face,  ex- 
tending from  the  inner  margin 
of  the  orbit  downwards  and 
outwards  to  the  anterior  bor- 
der of  the  masseter  muscle. 
Resting  on  the  same  plane  as 
the  facial  artery,  but  farther 
back,  and  less  tortuous,  it  still 
has  very  nearly  the  same  connexions  with  other  parts.  It  may  be  said 


FACIAL  VEIN. 


7 


to  commence  at  the  side  of  the  root  of  the  nose  by  a vein  formed  by 
the  junction  of  branches  from  the  forehead,  eyebrow,  and  nose,  and  to 
increase  by  receiving  others  during  its  course. 

The  frontal  vein,  [v.  frontalis,]  commences  on  the  roof  of  the  skull 
by  branches,  which  descend  obliquely  inwards  upon  the  forehead, 
maintaining  comrhunications  in  their  course  with  the  anterior 
branches  of  the  temporal  vein.  By  gradually  converging,  these 
branches  form  a vein  of  some  size,  which  descends  vertically,  parallel 
with  the  corresponding  vessel  of  the  opposite  side,  with  which  it  is 
connected  by  transverse  branches.  In  some  instances  the  veins  of  the 
two  sides  unite  and  form  a short  trunk,  which  again  divides  into  two 
branches  at  the  root  of  the  nose.  These  branches  diverge  as  they  run 
along  the  sides  of  the  nose  at  its  root,  where  each  becomes  continuous 
with  the  corresponding  angular  vein.  As  it  descends  from  the  fore- 
head, the  frontal  vein  receives  a branch  from  the  eyebrow,  and  some, 
of  smaller  size,  from  the  nose  and  upper  eyelid. 

The  supra-orbital  vein  (u.  supercilii)  runs  inwards  in  the  direction 
of  the  eyebrow,  covered  by  the  occipito-frontal  muscle.  Its  branches 
are  connected  externally  with  those  of  the  external  palpebral  and 
superficial  temporal  veins ; in  its  course  it  receives  branches  from  the 
contiguous  muscles  and  integument,  and  at  the  inner  angle  of  the  orbit 
inclines  downwards,  to  terminate  in  the  frontal  vein. 

The  supra-orbital  and  frontal  veins,  by  their  junction,  form  the 
angular  vein,  which  is  perceptible  beneath  the  skin  as  it  runs  obliquely 
downwards  and  outwards  by  the  inner  margin  of  the  orbit,  resting 
against  the  side  of  the  nose  at  its  root.  This  vessel  receives  by  its 
inner  side  the  nasal  veins,  which  pass  upwards  obliquely  to  join  it 
from  the  side  and  ridge  of  the  nose ; whilst  some  small  palpebral  veins 
open  into  it  from  the  opposite  direction.  Opposite  the  lower  margin 
of  the  orbit,  the  angular  vein  may  be  said  to  terminate  by  becoming 
continuous  with  the  facial  vein. 

The  facial  vein,  commencing  as  has  been  just  stated,  gradually 
increases,  as  it  receives  branches  from  the  lower  eyelid,  from  the  ala 
of  the  nose,  and  from  the  upper  lip.  By  its  outer  side  it  receives  two 
or  three  veins  {inferior  palpebral),  which  are  formed  by  small  branches 
derived  from  the  lower  eyelid,  from  the  outer  side  of  the  orbit,  and 
from  the  cheek.  The  direction  of  these  palpebral  branches  is  obliquely 
inwards  above  the  zygomatic  muscle,  beneath  which  they  turn  pre- 
viously to  their  termination.  On  a level  with  the  angle  of  the  mouth, 
the  facial  vein  receives  communicating  branches  (deep  facial)  from 
the  pterygoid  plexus,  and  also  some  branches  proceeding  from  the 
orbit,  furnished  by  the  infra-orbital  and  other  branches  of  the  internal 
maxillary  vein.  In  front,  the  facial  vein  is  further  increased  by 
branches  from  the  lips  (labial),  and  behind  by  others  from  the  cheek 
(buccal);  still  lower  down,  by  branches  from  the  masseter  muscle 
(masseteric)  on  the  one  hand,  and  from  the  chin  on  the  other.  Having 
reached  the  base  of  the  lower  maxilla,  the  vein  inclines  outwards  and 
backwards,  covered  by  the  cervical  fascia  and  the  platysma  muscle; 
and  soon  unites  with  a large  branch  of  communication  derived  from 
the  temporal  vein,  to  form  a vessel  of  considerable  size,  which  joins 
obliquely  the  trunk  of  the  internal  jugular  vein,  k. 


8 


TEMPORAL  VEIN. 


Previously  to  its  termination,  the  facial  vein  receives  the  follow'ing 
branches:  The  ranine  vein,  a small  vessel  which  lies  along  the  under 
surface  of  the  tongue,  close  by  the  frienum  linguae,  in  apposition  with 
the  artery  of  the  same  name;  its  course  is  backwards  and  outwards, 
between  the  mylo-hyoid  and  hyo-glossus  muscles,  to  open  into  the 
facial  vein,  or  sometimes  into  the  lingual.  The  silbmental  vein,  larger 
tlian  the  preceding,  commences  in  the  sublingual  gland,  from  which 
it  passes  backwards  in  the  course  of  the  duct;  it  receives  branches 
from  the  submaxillary  gland,  and  from  the  mylo-hyoid  muscle,  and, 
keeping  close  under  cover  of  the  margin  of  the  jaw-bone,  joins  the 
facial  vein;  but  in  some  instances  enters  the  lingual  or  superior  thyroid 
vein.  The  palatine  vein  returns  the  blood  from  the  plexus  around  the 
tonsil  and  from  the  soft  palate;  it  passes  downwards,  deeply  seated 
by  the  side  of  the  pharynx,  to  join  one  of  the  preceding  veins,  or  ter- 
minate in  the  facial  separately. 

TEMPORAL  VEIN. 

The  temporal  vein,  fig.  256,  h,  (vena  temporalis,)  a vessel  of  con- 
siderable size,  descends  in  front  of  the  external  auditory  tube,  reaching 
from  the  zygoma,  upon  which  it  rests,  to  the  angle  of  the  jaw,  and 
resulting  from  the  union  of  branches  which  are  spread  out  upon  the 
side  of  the  head,  some  being  superficial,  and  others  deeply  seated.  The 
superficial  branches  commence  upon  the  arch  of  the  skull,  where  they 
communicate  with  the  ramifications  of  the  frontal  and  occipital  veins, 
as  well  as  with  those  of  the  corresponding  vein  of  the  opposite  side. 
Those  from  the  fore  part  incline  downwards,  and  a little  backwards, 
whilst  the  posterior  branches  run  forwards  over  the  ear;  all  being 
placed  between  the  skin  and  the  temporal  fascia.  Converging  in  this 
way,  they  unite  at  an  angle  above  the  zygoma,  and  at  their  junction 
commences  the  trunk  of  the  temporal  vein.  To  the  same  point  also 
passes  a large  branch,  which  may  be  called  the  middle  temporal  vein, 
to  distinguish  it  from  those  which  are  still  deeper  seated  and  open  into 
the  internal  maxillary  vein.  This  vessel  arises  in  the  substance  of  the 
temporal  muscle,  from  which  the  branches  emerge,  to  form  a vessel 
of  some  size  upon  its  surface  ; this  vessel  pierces  the  fascia  at  the  upper 
border  of  the  zygoma,  and  opens  into  the  upper  part  of  the  common 
temporal  trunk  just  alluded  to.  The  temporal  vein  gradually  sinks 
into  the  substance  of  the  parotid  gland  as  it  descends  behind  the  ramus 
of  the  jaw.  Beneath  the  angle  of  that  bone,  it  divides  into  two  vessels, 
of  which  one,  ordinarily  the  larger,  inclines  inwards  to  join  with  the 
facial  vein,  whilst  the  other  turns  backwards,  and  becomes  continuous 
with  the  external  jugular  vein,  f.  The  branches  which  open  into  the 
temporal  vein  in  its  course  are  numerous: — parotid  branches,  from 
the  parotid  gland;  articular,  from  the  articulation  of  the  jaw;  anterior 
auricular  veins,  from  the  external  ear ; and  a vein  of  considerable  size, 
the  transverse  facial,  from  the  side  of  the  face.  This  last-named 
vessel  corresponds,  c,  with  the  transverse  artery  of  the  face.  It  courses 
backwards  from  the  side  of  the  face  to  the  temporal  vein.  From  the 
opposite  direction  the  temporal  vein  receives  ihe  posterior  auricular,  d, 
which  is  itself  joined  by  the  stylo-mastoid  vein. 


EXTERNAL  JUGULAR  VEIN. 


9 


Besides  these,  a branch  of  considerable  size  joins  the  temporal  vein 
in  the  substance  of  the  parotid  gland;  this  is  \S\q  internal  maxillary 
vein,  fig.  256,  e,  [v.  maxillaris  interna.]  It  corresponds  somewhat  in 
direction  and  position  with  the  artery  of  the  same  name,  and  receives 
branches  from  the  neighbouring  parts,  which  are  the  venae  comites  of 
the  divisions  of  the  internal  maxillary  artery.  Thus  three  or  four 
deep  temporal  branches  descend  from  the  temporal  muscle;  others 
come  from  the  pterygoid,  masseter,  and  buccinator  muscles.  The 
middle  meningeal  veins  and  some  palatine  veins  also  end  in  the  in- 
ternal maxillary;  and  lastly,  branches  from  the  surface  of  the  upper 
jaw,  and,  of  large  size,  from  the  lower  jaw,  emerging  from  the  dental 
foramen  {inferior  dental).  These  different  branches  form  a plexus  of 
veins,  named  pterygoid  plexus,  which  is  placed  in  the  lower  part  of  the 
temporal  fossa,  between  the  temporal  and  tlie  external  pterygoid 
muscle,  and  in  part  between  the  pterygoid  muscles.  It  communicates 
in  front  with  the  deep  facial  vein,  and  above,  with  the  cavernous 
sinus  by  branches  through  the  base  of  the  skull.  From  this  plexus 
proceed  one  or  two  short  trunks  {internal  maxillary)  which  join  nearly 
at  right  angles  with  the  temporal  vein. 

The  vessel  formed  by  the  junction  of  these  different  veins  from  the 
temple,  maxilla,  and  face,  may  be  called  the  temporo-maxillary  vein ; 
it  descends  in  the  interval  between  the  ramus  of  the  jaw  and  the  sterno- 
mastoid  muscle,  and  terminates  in  the  external  jugular  vein,/,  or  partly 
in  it  and  partly  in  the  internal  jugular  vein. 

EXTERNAL  JUGULAR  VEIN. 

The  external  jugular  vein,  fig.  256,  f,  [v.  jugularis  externa]  com- 
mences on  a level  with  the  angle  of  the  lower  maxilla,  at  the  end  of 
the  temporo-maxillary  vein,  and  therefore  receives  the  greater  part  of 
the  blood  returned  from  the  face  and  outside  of  the  cranium.  The 
external  jugular  vein  descends  perpendicularly  between  the  platysma 
and  sterno-mastoid  muscles.  In  consequence  of  the  oblique  direction 
forwards  of  the  last-named  muscle,  the  vein  gets  to  its  outer  border, 
close  by  which  it  continues  down  to  the  lower  part  of  the  neck,  where 
it  inclines  inwards  behind  the  muscle,  to  terminate  (either  as  a single 
trunk,  or  by  two  or  three  branches)  in  the  subclavian  vein,  m,  near  its 
junction  with  the  internal  jugular.  In  this  course  it  receives  one  or 
two  large  branches  from  the  back  of  the  neck ; one  of  these,  g,  {poste- 
rior external  jugular,)  lying  at  first  between  the  splenius  and  trapezius, 
passes  down  at  the  outside  of  the  jugular  vein,  and  below  the  middle 
of  the  neck  opens  into  it.  Superficial  branches  also  join  it  from  the 
fore  part  of  the  neck.  Some  of  these  commence  over  the  submaxil- 
lary gland,  and  some  under  the  chin ; by  converging,  they  often  form 
a vein  of  considerable  size,  h,  which  is  then  called  the  anterior  jugular 
vein.  This  vessel  lies  along  the  fore  part  of  the  neck,  sometimes  near 
the  sterno-mastoid  muscle,  and  terminates  either  by  inclining  outwards 
to  join  the  external  jugular  vein,  or,  after  giving  to  it  a branch  of 
communication,  sinks  beneath  the  sterno-mastoid  muscle,  and  ends  in 
the  internal  jugular  vein.  Previously  to  the  termination  of  the  externa! 
jugular  vein,  two  large  veins  open  into  it,  derived  from  the  region  of 


10 


INTERNAL  JUGULAR  VEIN. 


the  scapula,  i,  (supra-scajpular  and  posterior  scapular.)  Their  direction 
is  transverse  from  without  inwards,  lying  parallel  with  the  arteries  of 
the  same  name. 

As  already  mentioned,  the  external  jugular  vein  is  usually  provided 
with  twm  valves. 

INTERNAL  JUGULAR  VEIN. 

The  internal  jugular  vein,  fig.  256,  h,  [v.  jugularis  interna.] — The 
blood  from  the  brain  and  cranial  cavity  is  received  by  the  internal 
jugular  veins,  which  are  continuous  at  their  upper  extremities  with  the 
lateral  sinuses,  whilst  inferiorly  they  terminate  in  the  innominate  or 
brachio-cephalic  veins.  The  commencement  of  each  internal  jugular 
vein  at  the  lateral  sinus  is  at  the  broad  part  of  the  foramen  lacerum 
{jugular  fossa).  This  part  of  the  vessel,  being  somewhat  enlarged, 
has  been  named  the  sinus,  or  gulf  of  the  internal  jugular  vein.  Beneath 
the  skull,  the  vein  is  supported  by  the  rectus  lateralis  muscle,  and  lies 
close  at  the  outer  side  of  the  internal  carotid  artery,  as  far  as  the  cornu 
of  the  os  hyoides. 

Being  joined  at  this  point  by  the  common  trunk  formed  by  the  union 
of  the  facial  with  a part  of  the  temporal  vein,  the  internal  jugular  vein 
becomes  considerably  enlarged,  and  then  descends  parallel  with  the 
common  carotid  artery,  lying  at  its  outer  side  and  enclosed  in  the 
same  sheath,  together  with  the  vagus  nerve.  At  the  root  of  the  neck 
it  joins  nearly  at  a right  angle  with  the  subclavian  vein,  and  so  forms 
the  innominate  or  brachio-cephalic  vein.  Previously  to  its  junction 
with  the  facial  vein,  the  internal  jugular  receives  branches  from  the 
tongue,  the  pharynx,  and  the  occiput.  These  branches,  however,  or 
some  of  them,  are  very  frequently  found  to  end  in  the  common  trunk 
of  the  temporal  and  facial  veins.  The  Ungual  vein  commences  at  the 
side  and  upper  surface  of  the  tongue,  passes  backwards,  receiving 
branches  from  the  sublingual  gland  ; occasionally  the  ranine  vein  joins 
it,  and  sometimes  also  the  pharyngeal.  In  either  case  it  passes  back- 
wards between  the  mylo-hyoid  and  hyo-glossus  muscles,  to  open  into 
the  internal  jugular  vein.  The  pharyngeal  vein  commences  at  the 
back  and  sides  of  the  pharynx,  and  sometimes  ends  in  the  superior 
thyroid  vein,  and  sometimes  in  the  lingual,  or  separately  in  the  internal 
jugular  vein. 

Corresponding  in  course  and  distribution  with  the  occipital  artery 
there  is  an  occipital  vein,  which  communicates  with  a plexus  of  veins 
upon  the  occiput,  and  terminates  occasionally  in  the  external  jugular 
vein,  but  more  frequently  in  the  internal. 

The  laryngeal  vein  receives  branches  from  the  larynx  through  the 
thyro-hyoid  membrane;  they  unite  and  form  one  vein,  which  opens 
into  the  internal  jugular,  or  into  the  temporo-maxillary  venous  trunk, 
or  sometimes  into  the  superior  thyroid  vein. 

The  superior  thyroid  vein  commences  by  branches  in  the  thyroid 
body,  in  company  with  those  of  the  superior  thyroid  artery.  These 
unite  and  form  a single  vessel,  which  runs  transversely  outwards,  and 
opens  into  the  internal  jugular  vein.  Lower  down  is  found  another 
branch  {middle  thyroid),  also  derived  from  the  thyroid  body. 


VEINS  OF  THE  ARM. 


11 


VEINS  OF  THE  UPPER  LIMB. 


The  veins  of  the  upper  limb  are  divisible  into  257. 

two  sets,  one  being  superficial,  the  other  deep- 
seated.  Both  these  sets  of  veins,  as  high  up  as 
the  axillary,  and  including  that  vein,  are  provided 
with  valves,  which  are  more  numerous  in  the 
deep  than  in  the  subcutaneous  veins.  Valves  are 
constantly  to  be  found  at  the  entrance  of  branches 
into  the  main  vessels. 

The  superficial  veins. — These  are  much  the 
larger,  and  lie  between  the  skin  and  fascia. 

Commencing  on  the  dorsal  surface  of  the  fingers, 
they  converge  and  communicate  with  one  an- 
other on  the  back  of  the  hand,  so  as  to  form  a 
sort  of  plexus,  from  which  issue  two  chief  veins, 
that  take,  one  the  radial,  the  other  the  ulnar  bor- 
der of  the  fore-arm. 

The  radial  cutaneous  vein,  fig.  257,  a,  [v.  sub- 
cutanea  radialis  s.  cephalica.] — The  radial  cuta- 
neous vein  commences  by  branches  upon  the 
dorsal  surface  of  the  thumb  and  fore-finger. 

These  ascend  over  the  outer  border  of  the  wrist, 
and  form  by  their  union  a large  vessel,  which 
passes  along  the  radial  border  of  the  fore-arm, 
receiving  numerous  branches  from  its  anterior 
and  posterior  surfaces.  At  the  bend  of  the  arm  it 
receives  a branch  from  the  median  vein,  (me- 
dian-cephalic,) and  then  continues  its  course  at 
the  outer  side  of  the  upper  arm,  and  is  named 
“ cephalic”  vein. 

The  cephalic  vein,  b,  thus  formed,  ascends  along  the  outer  border 
of  the  biceps  muscle,  and  then  in  the  interval  between  the  great 
pectoral  and  deltoid  muscles,  and  finally  terminates  in  the  axillary 
vein,  between  the  coracoid  process  and  the  clavicle. 

[Occasionally  the  cephalic  vein  is  found  passing  over  the  clavicle  and  termi- 
nating in  the  jugular  vein.] 


The  ulnar  cutaneous  veins  [subcutanem  ulnares,  s.  basilicae]. — There 
are  two  ulnar  cutaneous  veins,  one  on  the  front,  the  other  on  the  back 
part  of  the  fore-arm.  The  posterior  ulnar  cutaneous  vein,  d,  begins 
on  the  back  of  the  hand  by  branches,  which  unite  to  form  a vein 
placed  over  the  fourth  metacarpal  space,  and  called  by  some  of  the 
older  anatomists  “ vena  salvatella.”  This  proceeds  along  the  ulnar 
border  of  the  fore-arm,  at  its  posterior  aspect,  and,  somewhat  below 
the  bend  of  the  elbow,  turns  forwards  to  join  with  the  anterior  ulnar 
cutaneous  vein.  The  anterior  ulnar  cutaneous  vein,  c,  commences 
upon  the  anterior  surface  of  the  wrist,  and  thence  ascends  along  the 
fore-arm,  communicating  by  branches  with  the  .median  vein  on  the 
one  hand,  and  with  the  posterior  ulnar  cutaneous  on  the  other.  From 
the  bend  of  the  elbow  upwards  the  trunk  formed  by  the  union  of  the 
two  ulnar  cutaneous  veins  assumes  the  name  of  “ basilic  vein.” 


12 


VEINS  OF  THE  ARM. 


The  basilic  vein,  e,  is  usually  of  considerable  size ; it  receives  at  its 
origin  a branch  from  the  median  vein,  g,  (median-basilic,)  and 
ascending  along  the  inner  border  of  the  biceps  muscle,  in  front  of  the 
brachial  artery,  terminates  in  one  of  the  venae  comites  of  that  vessel, 
or  in  the  axillary  vein,  which  it  chiefly  forms. 

The  median  cutaneous  vein  [vena  mediana]  of  the  fore-arm,  f, 
results  from  the  union,  on  the  anterior  part  of  the  fore-arm,  of  several 
branches.  It  is  a short  trunk,  which  serves  as  a means  of  communi- 
cation between  the  ulnar  and  radial  cutaneous  veins  on  each  side,  as 
well  as  between  the  superficial  and  deep  veins  of  the  arm.  Its  length 
is  subject  to  many  varieties ; it  terminates  by  dividing  into  two  branches, 
which  diverge  upwards  from  each  other.  One  of  these,  inclining 
inw'ards  to  join  the  basilic  vein,  and  thence  named  median  basilic,  g, 
passes  in  front  of  the  brachial  artery,  from  which  it  is  separated  by 
the  fibrous  expansion  given  by  the  tendon  of  the  biceps  muscle  to  the 
fascia  covering  the  flexor  muscles;  it  is  crossed  by  branches  of  the 
internal  cutaneous  nerve : the  other  division,  h,  {median  cephalic,) 
directed  outwards,  unites  with  the  cephalic  vein,  branches  of  the 
external  cutaneous  nerve  crossing  behind  this  vein.  The  upper  part 
of  the  median  vein  is  also  connected  with  the  deep  veins  by  a short 
branch,  which  sinks  beneath  the  muscles,  and  joins  the  veins  accom- 
panying the  brachial  artery. 

[As  frequent  an  arrangement,  as  the  division  of  the  median  vein  into  the  median 
basilic  and  cephalic,  is,  for  it  to  join  a short  trunk,  usually  varying  from  three  to 
four  inches,  crossing  over  the  aponeurotic  slip  from  the  tendon  of  the  biceps  at 
the  bend  of  the  arm,  obliquely  from  the  cephalic  to  the  basilic  vein.  In  such 
cases  the  median  vein  most  usually  forms  a junction  with  the  oblique  trunk 
nearer  to  the  basilic  than  the  cephalic  vein,  and  sometimes  the  median  joins  the 
basilic,  and  the  oblique  trunk  terminates  in  it  at  its  junction  with  the  basilic. 
Occasionally  the  median  vein  preserves  a distinct  course  up  the  arm,  and  termi- 
nates in  the  brachial  or  axillary  veins. 

In  bleeding  in  the  arm,  the  median  basilic  vein,  or  the  oblique  trunk  nearer  its 
junction  with  the  basilic,  is  most  generally  chosen,  because  of  its  usually  greater 
volume  than  the  median  cephalic  or  the  oblique  trunk  near  the  cephalic ; but  the 
intelligent  practitioner  should  keep  it  constantly  in  miird,  that  the  external  branch 
of  the  internal  cutaneous  nerve  most  usually  passes  over  the  median  basilic  or 
oblique  trunk,  near  the  basilic,  and  is  liable  to  be  cut.  The  external  cutaneous 
nerve  passes  beneath  the  median  cephalic  vein. — J.  L.] 

The  deep  veins  of  the  upper  limb. — The  brachial  artery,  its  imme- 
diate branches,  and  their  several  divisions,  are  each  accompanied  by 
two  veins,  named  vencE  comites.  These  companion  veins  lie  one  on 
each  side  of  the  corresponding  artery,  and  are  connected  with  each 
other  at  intervals  by  short  cross  branches,  which  in  some  places 
surround  the  artery. 

The  deep  ulnar  veins,  or  the  companion  veins  of  the  ulnar  artery. — 
On  examining  the  hand,  it  will  be  found  that  two  small  digital  veins 
accompany  each  digital  artery  along  the  side  of  the  phalanges.  At 
the  clefts  between  the  fingers,  the  two  small  veins  from  each  finger 
are  united  into  single  trunks,  which  continue  together  along  the  inter- 
osseous spaces  in  the  palm  of  the  hand,  and  terminate  in  the  two 
superficial  palmar  veins.  From  this  double  venous  arch  two  branches 
proceed  at  each  side  of  the  w’rist,  the  external  following  the  course  of 
the  superficial  volar  artery,  whilst  those  on  the  inner  side  accompany 


VEIxMS  OF  THE  ARM. 


13 


the  ulnar  artery.  The  two  deep  ulnar  veins,  commencing  thus  at  the 
inner  side  of  the  superficial  palmar  arch,  pass  in  front  of  the  wrist, 
where  they  communicate  with  the  interosseous  and  the  superficial 
veins;  then  proceeding  upwards  along  the  inner  side  of  the  fore-arm, 
one  on  each  side  of  the  ulnar  artery,  they  receive  several  branches 
from  the  neighbouring  muscles;  and,  lastly,  being  joined  by  the  veins 
which  accompany  the  interosseous  and  ulnar  recurrent  arteries,  unite 
with  the  deep  radial  veins  to  form  the  venae  comites  of  the  brachial 
artery. 

The  interosseous  veins  consist  of  two  sets  (anterior  and  posterior), 
corresponding  to  the  arteries  with  which  they  are  associated.  The 
anterior  interosseous  veins  commence  in  front  of  the  wrist-joint,  where 
they  communicate  freely  with  the  deep  radial  and  ulnar  veins.  In 
their  course  upwards  they  are  joined  by  several  small  branches,  and 
are  connected  at  the  upper  part  of  the  fore-arm  with  the  posterior 
veins  by  means  of  branches  which  pass  through  the  interosseous 
membrane  near  the  elbow-joint ; after  being  joined  by  the  posterior 
interosseous  veins,  they  end  in  the  venae  comites  of  the  ulnar  artery. 
The  veins  which  accompany  the  posterior  interosseous  artery,  pre- 
viously to  passing  from  behind  to  join  with  the  anterior  veins,  commu- 
nicate by  their  smaller  branches  with  the  ulnar  cutaneous  veins,  and 
through  branches  accompanying  the  recurrent  interosseous  artery, 
with  the  cephalic  vein. 

The  small  branches  which  unite  to  form  the  deep  radial  veins  run 
along  the  interosseous  muscles  in  the  palm  of  the  hand;  they  are 
united  in  front  with  the  digital  veins  previously  described,  and,  at 
each  end  of  the  interosseous  spaces,  are  connected  by  perforating 
branches  with  small  veins  situated  on  the  back  of  the  hand  ; by  uniting 
across  the  bases  of  the  metacarpal  bones,  they  form  a double  venous 
arch  corresponding  wdth  that  formed  by  the  radial  artery.  These 
deep  palmar  veins  communicate  on  the  inner  side  with  the  superficial 
arch  of  veins,  and  on  the  outer  side  end  in  the  companion  veins  of  the 
radial  artery.  The  deep  radial  veins,  in  passing  upwmrds  to  the  fore- 
arm, receive  at  the  wrist  a dorsal  branch,  and  one  which  passes  over 
the  small  muscles  of  the  thumb,  with  the  superficial  volar  artery;  then 
pursuing  the  course  of  the  radial  artery,  they  are  joined  by  small  veins 
from  the  surrounding  parts,  and  end  in  the  venae  comites  of  the  brachial 
artery. 

The  two  iracliial  veins,  [venae  brachiales,]  resulting  from  the  union 
of  the  deep  ulnar  and  radial  veins  just  described,  follow,  like  the 
several  vessels  of  the  same  class,  the  course  of  the  artery  with  which 
they  are  associated.  They  are  joined  in  their  progress,  from  the 
bend  of  the  elbow  upwards  on  the  arm,  by  the  veins  which  accompany 
the  branches  of  the  brachial  artery,  namely,  the  anastomotic  and  the 
two  profunda  arteries  of  the  arm.  At  the  lower  margin  of  the  axilla, 
the  brachial  veins  unite  to  form  the  axillary ; not  unfrequently,  how- 
ever, one  of  them  will  be  found  to  come  forward  and  unite  with  the 
basilic,  which  soon  becomes  continuous  with  the  axillary  vein. 

Between  the  several  veins  of  the  upper  limb  hitherto  described, 
numerous  connexions  exist  in  their  whole  course.  Thus,  those  which 

VOL.  II.  2 


14 


SUBCLAVIAN  VEIN. 


lie  beneath  the  integument  ai’e  connected  one  to  the  other  by  branches 
in  the  hand  and  fore-arm.  Each  pair  of  companion  veins  is  also 
united  by  short  transverse  vessels  crossing  the  artery  which  they 
accompany,  whilst  between  those  attending  different  arteries  frequent 
communications  exist.  Lastly,  as  has  been  in  many  instances  specially 
indicated,  the  subcutaneous  and  the  deep  veins  communicate  freely, 
especially  in  the  neighbourhood  of  joints.  This  general  anastomosis 
insures  the  continuance  of  the  circulation,  during  muscular  action,  in 
the  frequent  and  varied  motions  of  the  limb. 

AXILLARY  VEIN. 

The  axillary  vein  [v.  axillaris]  extends,  like  the  corresponding 
artery,  from  the  lower  border  of  the  axilla  to  the  outer  margin  of  the 
first  rib ; it  is  covered  by  the  pectoral  muscles  and  the  costo-coracoid 
membrane,  and  is  placed  to  the  inner  side  and  in  front  of  the  axillary 
artery.  The  branches  which  open  into  the  axillary  vein  are  very 
numerous.  It  is  formed  below  by  the  union  of  the  companion  veins 
of  the  brachial  artery ; it  receives  the  subcutaneous  veins  of  the  arm 
— the  basilic  at  its  commencement,  the  cephalic  towards  its  termina- 
tion ; it  is  also  joined  by  the  several  veins  corresponding  with  the 
branches  of  the  axillary  artery,  viz.,  the  two  circuinjlex  and  the  suh- 

scapular  veins  from  the 
Fig.  258.  shoulder,  the  alar  veins 

from  the  axilla,  and  the 
inferior,  the  superior, 
and  acromial  thoracic 
veins  from  the  side  of 
the  chest.  The  axillary 
vein,  therefore,  returns 
all  the  blood  from  the 
upper  limb:  its  size  is 
very  considerable,  and 
it  is  the  highest  of  the 
veins  of  the  upper  limb 
in  which  valves  are 
found. 

SUBCLAVIAN  VEIN. 

The  subclavian  vein, 
fig.  258,  d,  [v.  subcla- 
via,]  is  the  continuation 
of  the  axillary,  but,  un- 
like it,  has  no  valves.  It 
extends  from  the  outer 
margin  of  the  first  rib  to 
the  inner  end  of  the  cla- 
vicle, behind  wdffch  it  is 
joined  by  the  internal 
jugular  vein,  c,  the  union 
forming  the  innominate 


THE  VERTEBRAL  AND  SUPERIOR  INTERCOSTAL  VEINS. 


15 


or  brachio-cephalic  vein,  e.  The  subclavian  vein  crosses  over  the 
first  rib,  and  behind  the  clavicle,  not  reaching  so  high  up  in  the  neck 
as  the  subclavian  artery;  it  is  covered  by  the  clavicle,  and  by  the 
subclavius  and  sterno-mastoid  muscles,  and  lies  on  a plane  anterior  to 
the  artery,  from  which,  while  resting  on  the  rib,  it  is  separated  by  the 
scalenus  anticus  muscle  and  the  phrenic  nerve. — On  the  outer  side  of 
the  last-named  muscle  it  receives  the  external  jugular  vein,  and  on  its 
inner  side  the  internal  jugular.  In  their  course  to  join  the  subclavian 
vein  both  jugular  vessels  pass  in  front  of  the  subclavian  artery,  and 
add  to  the  difficulty  of  placing  a ligature  on  that  vessel.  The  sub- 
clavian vein  also  receives  the  following  branches. 

The  vertebral  vein  [v.  vertebralis]  commencing  in  branches  which 
proceed  from  the  pericranium  and  the  deep  muscles  lying  behind  the 
foramen  magnum  of  the  occipital  bone,  passes  outwards  and  down- 
wards to  reach  the  foramen  in  the  transverse  process  of  the  atlas. 
Through  this  foramen,  and  through  the  canal  formed  by  the  corre- 
sponding foramina  of  the  other  cervical  vertebrae,  the  vein  next 
descends  with  the  vertebral  artery.  Emerging  at  the  foramen  in  the 
sixth  vertebra,  it  runs  forwards  and  downwards  to  join  the  subclavian 
vein,  close  to  its  termination;  a small  branch  sometimes  descends 
through  the  foramen  in  the  seventh  vertebra,  and  opens  separately 
into  the  same  vein.  The  vertebral  vein  is  joined  in  its  course  by 
several  branches  from  the  neighbouring  muscles ; also,  immediately 
before  its  termination,  by  a branch  corresponding  with  the  deep 
cervical  artery ; and  in  the  same  situation  by  another  branch  of  con- 
siderable size,  which  descends  in  front  of  the  bodies  and  transverse 
processes  of  the  vertebrae  of  the  neck.  It  communicates  frequently 
with  the  spinal  veins  in  the  neck,  both  with  those  on  the  outer  side, 
and  those  in  the  interior  of  the  spinal  canal. 

The  superior  intercostal  veins. — It  sometimes  happens  that  at  the 
right  side  the  veins  corresponding  with  the  superior  intercostal  artery 
pass  downwards  separately,  to  open  into  the  azygos  vein,  as  that 
vessel  arches  forwards  to  join  the  upper  vena  cava.  When  they  unite 
to  form  a single  vein,  its  size  is  much  inferior  to  that  on  the  left  side. 
The  left  superior  intercostal  vein,  fig.  258,  h,  varies  in  length  in  diffe- 
rent persons,  being  small  when  the  azygos  minor  is  large,  and  vice 
versa  ; usually  the  fifth  intercostal  branch  turns  upwards,  and  joins 
with  or  receives  the  fourth,  third,  second,  and  first,  as  it  passes  by  the 
heads  of  the  ribs.  At  the  second  vertebra,  it  inclines  forwards  and 
opens  into  the  left  innominate  vein.  It  receives  in  its  course  the  left 
bronchial  vein.  The  sixth  intercostal  vein  generally  crosses  the  spine, 
and  opens  separately  into  the  azygos  vein;  it  communicates  by  a small 
branch  with  the  small  azygos  vein,  and  also  with  the  left  superior  in- 
tercostal vein. 

The  left  superior  intercostal  vein  often  takes  the  opposite  course  to 
that  which  has  been  mentioned,  being  directed  downwards,  and  in  this 
case  it  joins  the  azygos  vein.  It  has  been  seen  to  end  in  the  azygos 
minor. 


16 


UPPER  VENA  CAVA. 


INNOMINATE  OR  BRACHIO-CEPHALIC  VEIN. 

The  blood  returned  from  the  upper  limbs  through  the  subclavian 
veins,  and  from  the  head  and  neck  by  the  jugular  veins,  is  poured  into 
two  trunks,  which  are  therefore  named  brachio-cephaJic.  These  ves- 
sels, lig.  ;358,  e,  e,  (called  also  innominate,  [vena  innominata]  from 
their  relation  to  the  innominate  arteries),  resulting  from  the  union  of 
the  subclavian  with  the  internal  jugular  vein  at  each  side,  commence 
opposite  the  inner  ends  of  the  clavicles,  and  terminate  a little  below 
the  cartilage  of  the  first  rib  on  the  right  side,  where,  by  uniting,  they 
form  the  upper  vena  cava,  a.  In  consequence  of  the  situation  of  the 
point  at  which  they  meet,  the  right  and  left  brachio-cephalic  veins 
difier  considerably  in  direction,  length  and  connexions.  That  of  the 
right  side  is  very  short,  and  nearly  vertical  in  its  direction  ; this  vein 
is  in  apposition,  on  the  right  side,  with  the  upper  part  of  the  right 
lung.  The  vein  of  the  left  side,  about  three  times  longer  than  the 
preceding,  is  directed  across  from  left  to  right,  at  the  same  time  in- 
clining somewhat  downwards:  it  crosses  behind  the  first  bone  of  the 
sternum,  separated  from  it  by  the  sterno-hyoid  and  sterno-thyroid 
muscles,  and  by  the  thymus  gland,  when  it  exists,  or  some  cellular 
tissue;  it  lies  in  front  of  the  three  primary  branches  given  off  from  the 
arch  of  the  aorta,  and  it  rests  upon  the  highest  part  of  the  arch.  The 
innominate  veins  have  no  valves. 

The  inferior  thyroid  veins  emerge  from  a sort  of  venous  plexus  on 
the  thyroid  body — those  of  opposite  sides  communicating  by  small 
branches  across  the  trachea.  The  vein  of  the  left  side  descends  in 
front  of  the  tracheaj  behind  the  sterno-thyroid  muscles,  and  ends  in 
the  left  brachio-cephalic  or  innominate  vein  : that  of  the  right  side 
inclines  outwards  in  some  degree,  and  opens  into  the  corresponding 
brachio-cephalic  vein,  or  into  the  angle  of  union  between  it  and  the 
vessel  of  the  opposite  side. 

The  internal  mammary  veins  follow  exactly  the  course  of  the  arte- 
ries of  the  same  name — two  veins  accompanying  each  branch  of  the 
arteries.  The  two  companion  veins  of  the  artery  arise  by  small 
branches,  derived  from  the  fore  part  of  the  walls  of  the  abdomen, 
w'here  they  anastomose  with  the  epigastric  veins  ; from  thence  pro- 
ceeding upwards  behind  the  cartilages  of  the  ribs  between  them  and 
the  pleura,  they  receive  the  anterior  intercostal  veins  which  correspond 
with  the  branches  of  the  internal  mammary  artery,  together  with  some 
small  diaphragmatic,  thymic,  and  mediastinal  veins,  and  finally,  after 
uniting  into  a single  trunk,  terminate — that  of  the  left  side  in  the  left 
brachio-cephalic  vein,  that  of  the  right  side  usually  in  the  vena  cava. 

UPPER  VENA  CAVA. 

The  upper  vena  cava,  fig.  2.58,  a,  [vena  cava  superior]  conveys  to 
the  heart  the  blood  which  is  returned  from  the  head,  the  neck,  the 
upper  limbs,  and  the  thorax.  It  extends  from  a little  below  the  carti- 
lage of  the  first  rib  on  the  right  side  of  the  sternum  to  the  base  of  the 
heart,  where  it  opens  into  the  right  auricle.  Its  course  is  .slightly 
curved,  the  convexity  of  the  curve  being  turned  to  the  right  side.  It 
has  no  valves.  At  about  an  inch  and  a half  above  its  termination,  it 


AZYGOS  VEIN. 


17 


is  invested  by  the  fibrous  layer  of  the  pericardium,  the  serous  mem- 
brane being  reflected  over  it.  The  upper  vena  cava  lies  immediately 
in  front  of  the  right  pulmonary  vessels,  and  between  the  right  lung 
and  the  aorta,  which  partly  overlap  it.  It  receives  several  small  veins 
from  the  pericardium  and  the  mediastinum,  and  lastly  is  joined  from 
behind  by  the  azygos  vein. 

In  several  instances,  the  two  innominate  veins,  which  usually  join  to  form  the 
vena  cava  superior,  have  been  seen  to  open  separately  into  the  right  auricle. 

The  innominate  vein  of  the  right  side,  in  these  cases,  continues  in  the  ordinary 
course  of  the  vena  cava ; whilst  the  left  vein,  after  sending  a branch  across  to  the 
other,  descends  to  the  left  side  of  the  heart,  and  ends  on  the  back  of  the  right 
auricle,  with  the  coronary  vein. 

This  arrangement  of  the  veins  is  natural  in  the  fcetus  at  an  early  period,  and  is 
also  met  with  as  a permanent  condition  in  birds  and  in  certain  mammalia. 

AZYGOS  VEIN. 

The  azygos  vein  (v.  sine  pari). — The  name  given  to  this  vein  signi- 
fies that  it  has  no  fellow  or  corresponding  vessel  (a  priv.  ^svywfii)  ; but 
it  cannot  be  applied  with  propriety,  inasmuch  as  there  is  a similar 
though  smaller  vessel  on  the  opposite  side  (azygos  minor).  The 
azygos  vein,  fig.  258,  f,  sometimes  commences  by  a small  branch  either 
from  the  inferior  cava,  where  that  vessel  turns  forwards  to  reach  the 
aortic  opening  in  the  diaphragm,  but  much  more  frequently  it  begins 
below  from  the  lumbar  veins  (ascending  lumbar)  of  the  right  side,  or 
sometimes  from  the  renal  vein.  Passing  from  the  abdomen  into  the 
thorax,  through  the  aortic  opening  in  the  diaphragm,  or  to  the  outer 
side  of  that  opening,  through  the  fibres  of  the  diaphragm,  the  azygos 
vein  ascends  on  the  bodies  of  the  dorsal  vertebne,  until  it  arrives  oppo- 
site the  root  of  the  right  lung,  over  which  it  arches  forward,  and  then 
opens  into  the  upper  vena  cava,  immediately  above  tbe  point  at  which 
that  vessel  is  invested  by  the  pericardium.  When  passing  through  the 
opening  in  the  diaphragm,  this  vein  is  accompanied  by  the  thoracic 
duct,  both  being  situated  on  the  right  side  of  the  aorta.  In  the  thorax, 
maintaining  the  same  position  with  respect  to  the  duct  and  the  oesopha- 
gus, it  crosses  in  front  of  the  intercostal  arteries,  and  is  covered  by  the 
pleura.  It  is  joined  by  the  several  veins  which  accompany  the  aortic 
intercostal  arteries  of  the  right  side,  and,  at  about  the  sixth  or  seventh 
dorsal  vertebra,  by  the  left  or  small  azygos  vein.  It  is  also  joined  by 
several  oesophageal  and  other  small  veins,  and  near  its  termination  by 
the  bronchial  vein  of  the  right  lung ; and  higher  up  is  connected  with 
the  left  superior  intercostal  vein.  As  it  communicates  below  with 
the  vena  cava  inferior  by  one  of  the  branches  of  that  large  vein,  while 
it  terminates  in  the  vena  cava  superior,  it  forms  a connexion  between 
those  two  vessels.  A few  valves  of  imperfect  formation  have  been 
found  in  the  azygos  vein;  its  branches  (intercostal  veins)  are  provided 
with  distinct  valves. 

The  left  or  small  azygos  vein,  fig.  258,  g,  commences  from  one  of 

The  azygos  vein  has  been  seen  to  receive  the  lower  vena  cava,  and,  in  such 
cases,  is  of  course  extremely  large  (seep.  28). 

In  one  instance,  Meckel  found  the  azygos  ending  in  the  subclavian  vein. 

2* 


18 


VEINS  OF  THE  SPINE  AND  CRANIUM. 


the  lumbar  veins  (ascending  lumbar),  or  from  the  left  renal  vein,  and 
having  entered  the  thorax  with  the  aorta,  or  through  the  crus  of  the 
diaphragm,  ascends  upon  the  spine  in  front  of  the  left  intercostal  arte- 
ries, and,  passing  behind  the  aorta,  opens  into  the  azygos  vein,  oppo- 
site the  sixth  or  seventh  dorsal  vertebra.  It  receives  the  lower  inter- 
costal veins  of  the  left  side. 

All  the  intercostal  veins  of  the  left  side  have,  in  a few  instances,  been  observed 
to  join  a single  vein,  which  ended  in  the  left  innominate.  This  arrangement 
corresponded  with  that  on  the  right  side  of  the  body. 

The  bronchial  veins  return  the  residue  of  the  blood  employed  in  the 
nutrition  of  the  lungs.  Their  course  is  determined  by  that  of  the 
bronchi,  which  support  them  as  they  pass  towards  the  root  of  the 
lungs.  The  bronchial  vein  of  the  right  side  opens  into  the  azygos 
vein  near  its  termination  ; that  of  the  opposite  side  ends  in  the  superior 
intercostal  vein. 

VEINS  OF  THE  SPINE  AND  CRANIUM. 

The  part  of  the  venous  system  contained  within  the  skull  and  spinal 
canal,  presents  certain  peculiarities  deserving  especial  notice.  In  the 
cranmm  we  find  a series  of  sinuses,  rey^resenting  at  once  reservoirs 
and  canals,  interywsed  between  the  smaller  venous  branches  and  the 
large  trunks  (internal  jugular)  which  transmit  it  towards  the  heart. 
The  sinuses  in  the  skull  are  formed  between  layers  of  the  dura  mater, 
their  cavities  being  lined  by  a continuation  of  the  internal  membrane 
of  the  veins:  they  are  very  numerous,  and  vary  considerably  in  form 
and  size.  Along  the  whole  length  of  the  spinal  canal  there  is  found  a 
series  of  venous  tubes  or  plexuses  which  present  some  analogy  to 
the  cranial  sinuses,  but  which  may  be  regarded  as  intermediate  in 
character  between  those  sinuses  and  the  veins  in  other  parts  of  the 
body.  The  spinal  veins  have  no  valves. 

The  veins  within  and  upon  the  spinal  column  may  be  distinguished 
into  the  following  sets:  a.  Those  placed  deeply  in  the  vertebral  grooves, 
and  resting  upon  the  spines  and  arches  of  the  vertebrae,  h.  The  veins 
of  the  spinal  cord  itself,  c.  Veins  lodged  within  the  bodies  of  the  ver- 
tebrae. cl.  Two  long  series  of  veins,  or  rather  venous  plexuses,  ex- 
tended behind  the  bodies  of  the  vertebrae  the  whole  length  of  the  canal, 
e.  Veins  on  the  fore  part  of  the  arches  of  the  vertebrae. — There  are 
likewise  branches  of  communication,  some  of  which  connect  all  the 
other  sets  together,  and  some  which  bring  them  into  connexion  with 
the  general  venous  system. 

Preparation  and  Dissection. — The  long  spinal  veins  were  first  described  by 
Chaussier ; the  veins  of  the  cranial  and  spinal  bones,  as  well  as  of  the  osseous 
system  generally,  were  subsequently  examined  with  great  care  by  Dupuytren, 
and  demonstrated  in  his  lectures  on  anatomy.  Breschet  subsequently  took  up 
the  subject.*  In  order  to  inject  these  vessels,  an  old  and  emaciated  subject 
should  be  chosen,  as  the  venous  system  becomes  more  developed  in  advanced 
age  y it  should  be  placed  in  a warm-bath  in  the  usual  way,  and  thoroughly  warmed 
previous  to  injection.  As  the  vessels  cannot  be  filled  from  any  single  vessel, 

* Essai  sur  les  Veines  du  Rachis.  4to. — Traite  Anatomique  sur  le  Systdme  Veineux. 
Fol.  avec  planches. 


VEINS  OF  THE  SPINE  AND  CRANIUM. 


19 


advantage  must  be  taken  of  their  numerous  connexions  to  inject  them  from  diffe- 
rent points..  With  this  view,  an  injecting  pipe  must  be  inserted  into  the  upper 
longitudinal  sinus,  and  others  into  the  azygos  vein,  and  into  the  upper  and  lower 
venffi  cavse.  Through  all  these  vessels  the  fluid  for  injecting  should  be  pushed, 
and  through  at  least  two  or  three  of  them,  if  possible,  at  the  same  time.  The 
posterior  and  external  veins  (if  the  injection  has  succeeded)  are  to  be  traced 
through  the  mass  of  dorsal  muscles;  those  within  the. spinal  canal  are  best  seen 
by  making  a vertical  section  of  the  spine  and  skull,  dividing  them  into  two  late- 
ral halves;  or  the  arches  of  the  vertebrae  may  be  cut  out,  and  the  cavity  exposed. 

a.  The  dorsal  veins  (dorsi-spinales, — Dupuytren,  Breschet). — The 
blood  from  the  muscles  and  integument  placed  along  the  back  of  the 
spine,  is  returned  by  a series  of  short  veins,  which  ramify  upon  the 
arches  and  spinous  processes  of  the  vertebrae,  and  run  forwards  to 
terminate  in  some  of  the  larger  veins  within  the  spinal  canal.  Com- 
mencing by  small  branches,  they  gradually  increase  in  size  as  they 
run  forwards,  close  by  the  spinous  processes ; on  reaching  the  interval 
between  the  arches  of  the  vertebrae,  they  pierce  the  ligamenta  subflava, 
to  terminate  in  a venous  plexus  within  the  canal.  Towards  the  outer 
part  of  the  intervertebral  grooves  another  set  of  veins  arise,  which 
pass  obliquely  inwards,  through  the  intertransverse  spaces,  in  company 
with  the  posterior  branches  of  the  lumbar  and  intercostal  arteries,  and 
open  into  the  veins  which  accompany  those  vessels. 

b.  The  veins  of  the  spinal  cord  (medulli-spinales, — Breschet)  ramify 
upon  the  cord  and  its  nerves,  enclosed  within  the  sheath  formed  by  the 
dura  mater.  Though  they  communicate  with  the  other  spinal  veins, 
they  are  not  injected  with  them,  even  when  the  injecting  process  above 
described  is  most  successful.  Breschet  gives  the  following  as  the  best 
method  of  demonstrating  them: 

Preparation. — Let  the  injection  consist  of  a strong  solution  of  isinglass,  coloured 
with  indigo  or  Prussian  blue : open  the  spinal  canal  in  the  lumbar  region,  slit  up 
the  dura  mater,  and  search  for  one  of  the  largest  of  the  veins  which  rest  upon  the 
cord ; into  this  pass  the  point  of  a very  small  injecting  pipe  and  then  cautiously 
push  the  injection,  for  the  coats  of  the  veins  are  exceedingly  thin  and  weak. 

The  veins  of  the  spinal  cord  are  very  small,  long,  and  tortuous ; they 
run  upon  both  surfaces  of  the  cord,  where  they  form  a diffused  plexus 
or  network.  They  become  larger,  for  the  most  part,  as  they  ascend, 
but  near  the  base  of  the  skull  are  smaller  than  in  the  lumbar  region. 
They  communicate  freely  with  the  spinal  veins  and  plexuses,  by  means 
of  branches  which  accompany  the  nerves  towards  the  intervertebral 
foramina.  Near  the  base  of  the  skull  these  veins  unite,  and  form  two 
or  three  small  trunks,  which  communicate  by  transverse  branches 
with  the  vertebral  veins,  and  then  terminate  in  the  inferior  cerebellar 
veins,  or  in  the  petrosal  sinuses. 

c.  The  veins  belonging  to  the  bodies  of  the  vertebrcB  (venae  basis 
vertebrarum, — Dupuytren;  veines  basi-vertdbrales, — Breschet)  are 
comparatively  large  vessels  contained  in  the  canals  within  the  bodies 
of  the  vertebrae ; the  arteries  which  may  accompany  them  being  very 
small.  About  the  middle  of  the  posterior  surface  of  each  vertebra, 
(and  this  is  especially  evident  in  the  dorsal  and  lumbar  regions,)  there 
is  found  a large  foramen  leading  into  a canal,  which,  running  forwards 
into  the  substance  of  the  bone  for  two  or  three  lines,  divides  into  two 


20 


POSTERIOR  SPINAL  VEINS. 


smaller  canals,  which  are  directed  towards  each  other,  and  often  unite 
together.  From  this,  still  smaller  canals  pass  obliquely  forwards,  some 
of  which  terminate  in  the  cancelli  of  the  bone,  whilst  others  open  upon 
its  anterior  or  convex  surface.  Within  these  canals  are  situated  the 
proper  veins  of  the  bodies  of  the  vertebrae.  They  anastomose  on  the 
front  of  the  bones  with  some  of  the  superficial  veins  ; and  the  trunk  of 
each  having  reached  the  spinal  canal  divides  into  two  branches,  M'hich 
diverge  and  terminate  in  the  large  spinal  veins  behind  the  bodies  of 
the  vertebrae. 

d.  The  blood  collected  by  the  different  vessels  here  described  is 
poured  by  them  into  two  large  veins,  or  rather  tortuous  venous  canals, 
w'hich  extend,  one  on  each  side,  along  the  whole  length  of  the  spinal 
canal  behind  the  bodies  of  the  vertebras.  These  vessels  may  be  named 
the  great  spinal  veins  (grandes  veines  rachidiennes  longitudinales  ante- 
rieures, — Breschet).  They  are  not  of  uniform  size  throughout,  but  are 
alternately  constricted  and  enlarged,  the  constricted  points  correspond- 
ing with  the  intervertebral  foramina,  where  they  are  drawn  forwards, 
and  in  a manner  secured  by  the  branches  of  communication  which 
pass  outwards.  This  long  series  of  veins  lies  behind  the  bodies  of  the 
vertebrae,  occupying  the  interval  at  each  side  between  the  interverte- 
bral foramina  and  the  orifices  seen  at  the  back  of  the  bodies  of  these 
bones.  In  some  parts  the  veins  are  double,  or  even  triple,  so  as  to 
form  a plexus;  and  occasionally  they  are  altogether  interrupted,  which 
shows  that  each  portion  may  be  regarded  as  a separate  trunk,  receiv- 
ing blood,  and  conveying  it  outwards  into  the  general  circulation,  and 
that  there  is  not  necessarily  an  ascending  or  descending  current  along 
the  venous  column,  formed  by  the  entire  series  of  veins.  In  the  thora- 
cic region  their  communicating  branches  open  into  the  intercostal 
veins,  in  the  loins  into  the  lumbar  veins,  in  the  neck  for  the  most  part 
into  the  vertebral. 

The  posterior  spinal  veins  (veines  longitudinales  rachidiennes  pos- 
terieures, — Breschet).  e.  Besides  this  anterior  set  of  veins  within 

the  spinal  canal,  there  is  a complex  intei’lacement  of  tortuous  veins 
established  along  the  inner  or  anterior  surface  of  the  arches  of  the 
vertebrae.  In  the  lower  part  of  the  canal  this  interlacement  of  veins 
is  not  so  close  as  in  the  upper  portion,  where  it  usually  conceals  (if 
the  injection  has  been  successful)  the  whole  surface  of  dura  nriater. 
These  veins  also  converge  to  the  intervertebral  foramina,  and  open  by 
rather  small  vessels  with  the  intercostal  veins. 

From  a consideration  of  the  connexion  and  arrangement  of  the  dif- 
ferent parts  of  these  complex  veins,  it  would  appear  that  the  blood  in 
each  part  flows  through  them  horizontally  from  behind  forwards. 
The  dorsal  veins  pour  their  blood  into  the  longitudinal  plexus  on  the 
inner  surface  of  the  arches  of  the  vertebrae ; from  thence  it  is  collected 
by  two  or  three  small  branches,  which  converge  to  the  intervertebral 
foramina,  and  open  into  some  of  the  veins  outside  the  vertebral  column 
in  front,  viz.,  into  the  lumbar,  azygos,  or  cervical  veins.  Into  these 
also,  the  contents  of  the  great  spinal  veins  are  conveyed  by  the  short 
communicating  branches  already  noticed. 


CRANIAL  SINUSES. 


21 


CEREBRAL  VEINS. 

The  part  of  the  venous  system  contained  within  the  skull  consists  of 
veins,  properly  so  called,  and  of  certain  cavities  or  channels  called 
sinuses.  The  veins  which  return  the  blood  from  the  brain  are  divisible 
into  two  sets,  one  being  on  tbe  surface,  the  other  in  the  interior  of  that 
organ.  The  superficial  veins  ramify'  upon  every  part  of  the  surface 
of  the  brain,  receiving  branches  on  the  one  hand  from  its  substance, 
and,  on  the  other,  terminating  in  the  different  sinuses.  Upon  the  upper 
surface  of  the  hemispheres  the  veins  will  be  seen  for  the  most  part 
lodged  in  the  tortuous  sulci,  between  the  convolutions ; but  some  will 
be  observed  to  run  over  the  convexity  of  the  convolutions.  Their 
general  direction  is  towards  the  middle  line ; and  on  reaching  the 
margin  of  the  longitudinal  fissure  between  tbe  hernispberes,  they^  receive 
branches  from  the  flat  surface  of  the  hemisphere,  and,  becoming  in- 
vested by  a tubular  sheath  of  the  arachnoid  membrane,  open  obliquely 
forwards  into  the  superior  longitudinal  sinus. 

The  veins  upon  the  sides,  and  under  surface  of  the  brain,  are  simi- 
larly arranged ; but  are  directed  outwards,  to  open  into  the  lateral 
sinuses  at  each  side. 

The  deep  veins  of  the  brain  commence  by  branches  within  the  ven- 
tricles of  that  organ.  Upon  the  surface  of  the  corpus  striatum,  for 
example,  several  minute  venous  branches  are  seen,  which  for  the  most 
part  converge,  to  form  a slender  vein  which  runs  along  the  groove 
between  the  corpus  striatum  and  optic  thalamus,  and  opens  into  one 
of  the  veins  of  the  choroid  plexus.  The  minute  veins  of  the  choroid 
plexus  pass  backward,  and  incline  towards  the  middle  line  from  each 
side,  so  as  to  form,  by  their  union,  two  veins  {vencB  Galeni).  These, 
lying  parallel,  run  directly  backwards,  enclosed  within  the  velum  in- 
terpositum,  and  escape  from  the  ventricle  by  passing  through  the 
great  transverse  fissure  of  the  brain  between  the  under  surface  of  the 
corpus  callosum  and  tubercula  quadrigemina.  In  this  way  they  reach 
the  anterior  margin  of  the  tentorium  cerebelli,  at  its  place  of  union 
with  the  falx  cerebri,  where  they  terminate  by  opening  into  the  straight 
sinus. 

The  veins  of  the  cereheJlum  are  disposed  in  two  sets,  not  merely 
from  a reference  to  their  position,  but  also  from  a consideration  of 
their  direction  and  termination.  Those  of  the  upper  surface  incline 
inwards  and  forwards  for  the  most  part,  and  will  be  found  to  run 
upon  the  upper  vermiform  process,  over  which  they  ascend  a little  to 
reach  the  straight  sinus,  in  which  they  terminate;  some,  farther  for- 
ward, open  into  the  veins  of  Galen.  Those  at  the  under  surface  run 
transversely  outwards,  and  pour  their  contents  into  the  two  lateral 
sinuses. 

CRANIAL  SINUSES. 

The  sinuses  placed  within  the  cranial  cavity,  are  interposed  between 
the  cerebral  veins  and  the  internal  jugular  veins,  which  receive  the 
blood  from  them.  There  are  several  of  these  canals,  and,  by  reason 
of  a difference  in  their  position,  they  admit  of  being  divided  into  two 


22 


CRANIAL  SINUSES. 


sets,  viz.,  those  placed  in  the  prominent  folds  of  the  dura  mater,  and 
those  disposed  at  the  base  of  the  skull. 

The  form  and  size  of  the  sinuses  are  various.  All  of  them  are  lined 
by  a continuation  of  the  internal  membrane  of  the  veins,  the  dura 
mater  serving  as  a substitute  for  the  external  coat. 

The  sinuses  which  are  contained  in  the  several  processes  or  folds 
of  the  dura  mater  converge  to  a common  point,  which  corresponds 
with  the  internal  occipital  protuberance,  and  is  called  the  conjluence 
of  the  sinuses,  or  torcular  Herophili,  fig.  259,  a;  fig.  260,  i:  its  form 
is  very  irregular.  If  a square  piece  of  bone  be  removed,  and  the 
dura  mater  be  laid  open  at  the  point  above  referred  to,  six  apertures 
leading  to  the  following  sinuses  will  be  observed  opening  into  it:  viz., 
one  to  the  longitudinal,  and  one  to  the  straight  sinus ; two  to  the  right 
and  left  lateral  sinuses ; and  two  to  the  posterior  occipital  sinuses. 

The  superior  longitudinal  sinus,  fig.  259,  b (sinus  longitudinalis ; s. 

falciformis  superior,)  commencing 
at  the  crista  galli,  extends  from 
before  backwards,  in  the  upper 
border  of  the  falx  cerebri,  gra- 
dually increasing  in  size  as  it  pro- 
ceeds. Across  its  cavity,  which 
is  triangular,  several  bands  {cliordce 
Willisii)  extend  obliquely.  The 
veins  from  the  cerebral  surface 
open  into  this  sinus  in  such  a way 
that  the  apertures  of  the  greater 
number  of  them  are  directed  from 
behind  forwards,  contrary  to  the 
direction  of  the  current  within  it. 
The  longitudinal  sinus  communi- 
cates with  the  veins  on  the  outside 
of  the  occipital  bone,  by  a branch  (one  of  the  “ emissary  veins,”  San- 
torini) which  passes  through  a hole  in  the  parietal  bone. 

The  inferior  longitudinal  sinus,  fig.  259,  c (s.  falciformis  inferior; 
sinus  longitudinalis  inferior),  is  very  small;  it  is  cii’cular  in  the  form 
of  its  cavity,  and  so  much  resembles  a vein,  that  it  is  sometimes  named 
inferior  longitudinal  vein.  Placed  in  the  inferior  concave  border  of 
the  falx  cerebri,  it  runs  from  before  backwards,  and  opens  into  the 
straight  sinus  on  reaching  the  anterior  margin  of  the  tentorium  cere- 
belli.  It  receives  branches  from  the  surface  of  the  falx  cerebri,  and 
sometimes  from  the  flat  surface  of  the  middle  and  posterior  lobes. 

The  straight  sinus,  fig.  259,  d (s.  quartus;  s.  tentorii). — This  sinus 
may  be  considered  as  the  continuation  of  the  inferior  longitudinal 
sinus;  it  runs  backwards  in  the  direction  of  the  base  of  the  falx  cere- 
bri, gradually  widening  as  it  approaches  the  torcular  Herophili,  in 
which  it  terminates.  Its  form  is  triangular ; some  transverse  bands 
cross  its  interior.  Besides  the  inferior  longitudinal  sinus,  the  venae 
Galeni,  e,  and  the  superior  veins  of  the  cerebellum,  open  into  it. 

The  lateral  sinuses,  fig.  259,  f;  fig.  260,  h,  (sinus  laterales ; s.  trans- 


Fig.  259. 


3 


CRANIAL  SINUSES. 


23 


versi,)  are  of  considerable  size.  Their  direction  conforms  to  that  of 
the  groove  marked  along  the  inner  surface  of  the  occipital  and  other 
bones,  from  opposite  the  internal  occipital  protuberance  to  the  foramen 
lacerum  posterius.  The  sinus  of  the  right  side  is  usually  larger  than 
that  of  the  left;  both  commence  at  the  torcular  Herophili,  and  termi- 
nate at  the  outlet  just  noticed,  where  they  are  continuous  with  the 
jugular  veins.  The  lateral  sinuses  receive  the  blood  transmitted  from 
both  the  longitudinal  sinuses,  from  the  straight  and  occipital  sinuses, 
and  also  that  from  the  veins  upon  the  sides  and  base  of  the  brain,  from 
those  on  the  under  surface  of  the  cerebellum,  and  from  some  of  the 
veins  of  the  diploe.  The  petrosal  sinuses  also  join  the  lateral  sinus  on 
each  side;  and  two  emissary  veins  connect  these  with  the  veins  at  the 
back  of  the  head  and  neck. 

The  posterior  occipital  sinus,  fig.  259,  g;  fig.  260,  g,  (sinus  occipi- 
talis posterior,)  is  sometimes  a single  canal,  not  unfrequently  double, 
as  if  composed  of  two  compartments.  It  lies  along  the  attached  bor- 
der of  the  falx  cerebelli,  extending  from  the  posterior  margin  of  the 
foramen  magnum  to  the  confluence  of  the  sinuses.  It  communicates 
in  front  with  the  posterior  spinal  plexuses  of  veins. 

The  sinuses  placed  at  the  base  of  the  skull  are  as  follow's,  taking 
them  in  their  order  from  before  backw'ards : 

The  circular  sinus,  fig.  260,  a (sinus  circularis, — Ridley). — The 
name  expresses  its  form ; its  position  is  around  the  margin  of  the  pitui- 
tary fossa.  It  is  not  always  a complete  ring,  as  it  represents  some- 
times a semicircle,  placed  usually  before  the  gland,  sometimes  behind 
it.  This  small  sinus  receives  the  blood  from  the  minute  veins  of  the 
pituitary  body.  It  communicates  at  each  side  with  the  cavernous 
sinus. 

The  cavernous  sinuses,  fig.  260,  b,  [sinus  cavernosi,]  two  in  number, 
are  placed  one  on  each  side  of  the  body  of  the  sphenoid  bone.  They 
are  of  a very  irregular  form,  but  of  considerable  size.  Each  receives 
the  ophthalmic  vein  at  its  fore  part,  and  communicates  internally  with 
the  circular  sinus,  and  posteriorly  with  the  petrosal  sinuses.  The  dura 
mater  at  the  side  of  the  body  of  the  sphenoid  bone  divides  into  two 
layers ; one  of  these  rests  on  the  bone,  whilst  the  other  is  stretched 
from  the  margin  of  the  sphenoidal  fissure  backwards,  to  the  upper 
border  of  the  petrous  portion  of  the  temporal  bone;  so  that  the  two 
layers  leave  an  interval  between  them,  constituting  the  sinus.  The 
membrane  which  lines  the  ophthalmic  vein  and  the  circular  sinus,  passes 
into  the  cavity  now  under  consideration;  it  is  intimately  connected 
with  that  layer  of  the  dura  mater  which  forms  the  inner  wall  of  the 
sinus,  but  is  separated  from  the  outer  wall  by  an  interval  in  which  are 
found  the  carotid  artery,  with  the  third,  fourth,  ophthalmic  division  of 
the  fifth,  and  the  sixth  nerves. 

The  upper  petrosal  sinus,  fig.  259,  h ; fig.  260,  d,  [sinus  petrosus 
superior,]  is  a narrow'  venous  canal,  running  along  the  upper  margin 
of  the  petrous  part  of  the  temporal  bone.  Commencing  at  the  back 
part  of  the  cavernous  sinus,  it  is  directed  outwards  and  backwards  in 
the  attached  margin  of  the  tentorium  cerebelli ; and  descending  a little, 
ends  in  the  lateral  sinus,  where  it  lies  upon  the  temporal  bone. 


24 


VEINS  OF  THE  DIPLOE. 


The  lower  petrosal  sinus,  fig.  259,  i ; 
fig.  260,  e,  [s.  petrosLis  inferior,]  larger 
than  the  preceding  sinus,  is  very  near 
that  sinus  at  its  anterior  end;  but  is 
afterwards  lower  down,  and  to  its  inner 
side.  Commencing  at  the  cavernous 
sinuses,  the  lower  petrosal  sinus  passes 
downwards  and  backwards  very  near 
it,  taking  the  direction  of  the  inferior 
margin  of  the  petrous  bone,  between  it 
and  the  basilar  process  of  the  occipital 
bone.  It  opens  into  the  lateral  sinus 
near  its  termination,  or  into  the  internal 
jugular  vein. 

The  anterior  occipital  or  transverse 
sinus,  fig.  260,/,  (sinus  basilaris). — This 
is  placed  at  the  fore  part  of  the  basilar 
process  of  the  occipital  bone,  and  is 
rather  a plexus  of  veins  than  a sinus,  which  reaches  transversely,  so 
as  to  establish  a communication  between  the  inferior  petrosal  and  the 
cavernous  sinuses. 

OPHTHALMIC  VEIN. 

The  ophthalmic  vein,  fig.  260,  c,  [v.  ophthalmica,]  may  be  described 
in  connexion  with  the  veins  of  the  cranium  as  it  opens  into  the  cavern- 
ous sinus.  Its  branches  are  distributed  in  the  difi'erent  structures  con- 
tained within  the  orbit,  in  company  with  the  branches  of  the  ophthal- 
mic artery.  Some  small  ramifications  arise  from  the  eyelids,  whilst 
others  communicate  with  the  angular  branch  of  the  facial  vein  ; those 
which  accompany  the  supra-orbital  artery  have  similar  connexions 
with  the  veins  upon  the  forehead.  All  these  branches,  together  with 
others  arising  from  the  lachrymal  gland,  from  the  different  muscles, 
from  the  ethmoidal  cells,  those  from  the  globe  of  the  eye  itself,  all 
named  according  to  the  arterial  branches  which  they  accompany, 
join  to  form  a short  single  trunk,  which  leaves  the  orbit  by  the  inner 
part  of  the  sphenoidal  fissure,  and  terminates  in  the  cavernous  sinus. 

VEINS  OF  THE  DIPLOE. 

The  veins  of  the  cranial  bones,  veins  of  the  diploe,  [v.  diploicse,]  are 
only  to  be  seen  after  the  pericranium  is  detached,  and  the  external 
table  of  the  skull  carefully  removed  by  aid  of  a file.  Lodged  in  proper 
canals  hollowed  in  the  substance  of  the  bones,  their  branches  form  an 
irregular  network,  from  which  a few  larger  vessels  issue.  These  are 
directed  downwards  at  different  parts  of  the  cranium,  and  terminate, 
partly  in  the  veins  on  the  outer  surface  of  the  bones,  and  partly  in  the 
lateral  sinuses,  or  the  posterior  occipital  sinuses.  Amongst  them  may 
be  recognised  generally,  a frontal  vein  of  the  diploe;  two  temporal, 
one  anterior  ramifying  in  the  frontal  bone,  and  one  posterior  chiefly 
coming  from  the  parietal  bone;  and  lastly,  the  largest  vein  of  the 
diploe,  that  ramifying  in  the  occipital  bone. 


Fig.  2G0. 


VEINS  WHICH  FORM  THE  LOWER  VENA  CAVA. 


25 


OF  THE  VEINS  WHICH  FORM  THE  LOWER  VENA  CAVA. 

The  branches  which  unite  to  form  the  lower  vena  cava  return  the 
blood  from  the  lower  limbs,  and  from  the  viscera  of  the  pelvis  and 
abdomen. 

The  veins  of  the  lower  limb,  as  in  other  parts  of  the  body,  are 
divisible  into  two  sets,  of  which  one  is  deeply-seated,  whilst  the  other 
runs  between  the  common  integument  and  the  fascia.  All  the  veins 
of  the  lower  limb,  as  high  as  the  femoral  venous 
trunk,  are  provided  with  valves,  and  they  are  Fig-  261. 

said  to  be  more  numerous  than  in  the  veins  of 
the  upper  limb.  The  deep  veins  have  more 
valves  than  the  subcutaneous  set;  and  each 
branch  has  two  valves  placed  to  guard  its  en- 
trance into  a larger  trunk.  Immediately  be- 
neath the  integument  on  the  dorsum  of  the 
foot  there  exists  a network  of  small  veins,  from 
which  issue  two  principal  trunks  (saphenous), 
which  are  named,  from  their  relative  position, 
internal  and  external,  or,  from  their  relative 
length,  the  long  and  short. 

saphenous  vein,  fig. 
s.  interna,]  extends 
an  inch  and  a half 
this  course  it  lies 


in 


The  long  or  internal 
261,  [v.  saphena  magna 
from  the  ankle  to  within 
of  Poupart’s  ligament ; 
between  the  integument  and  the  fascia.  Tak- 
ing rise  from  the  plexus  of  veins  on  the  dorsum 
of  the  foot,  it  passes  upwards  in  front  of  the 
inner  ankle,  and  thence  along  the  correspond- 
ing border  of  the  tibia,  accompanied  by  the 
internal  saphenous  nerve.  At  the  knee,  the  vein 
inclines  a little  backwards  as  it  passes  by  the 
inner  condyle;  after  which  it  ascends  along  the 
inner  and  fore  part  of  the  thigh,  and  tenninates 
in  the  femoral  vein,  after  passing  through  an 
aperture,  1,  in  the  fascia  lata,  which,  from  this 
circumstance,  has  been  termed  the  saphenous 
opening.  It  is  joined  in  this  long  course  by 
numerous  cutaneous  branches,  and  near  its  ter- 
mination receives  the  superficial  epigastric,  a ; 
external  pudic,  b ; and  supeificial  circumflex  iliac 
veins,  c ; the  former  passing  down  from  the  ab- 
domen between  the  layers  of  the  superficial 
fascia,  the  latter  from  the  groin  and  pubes. 
This  long  vein  has  a variable  number  of  valves. 
Sometimes  six  sets  have  been  counted.  In  other 
cases  only  four,  or  even  two.  There  are  more 
in  its  course  through  the  thigh  than  in  the  leg. 

The  external  or  short  saphenous  vein  [v. 
saphena  minor,  s.  posterior]  proceeds  from 
branches,  d,  which  arise  along  the  outer  side  of 

VOL.  II.  3 


26 


FEMORAL  VEIN. 


Fig.  262. 


the  dorsum  of  tlie  foot,  and  passes  behind  the  outer  ankle,  gradually 
inclining  backwards  to  the  tendo  Achillis.  Passing  along  the  border 
of  the  tendon,  it  gets  on  the  belly  of  the  gastrocnemius  muscle,  fig. 
262,  on  which  it  ascends,  accompanied  by  the  external  saphenous 
nerve ; with  the  nerve  it  runs  between  the  heads  of  the  gastrocne- 
mius, and  pours  its  contents  into  the  popliteal  vein. 

The  deep  veins  of  the  low'er  limb  accompany  the  arteries  and  their 
branches,  following  exactly  their  distribution.  Those  below  the  knee 
being  for  the  most  part  disposed  in  pairs,  and  presenting  the  disposition 
described  in  the  corresponding  veins  of  the  upper  limb,  are  named  the 
vencB  comites  of  the  vessels  with  which  they  are  associated.  The  venae 
comites  of  the  arteries  of  the  leg,  namely,  the  anterior  and  posterior 
tibial  veins  (the  latter  having  previously  received  the  peroneal),  unite 
near  the  lower  border  of  the  popliteus  muscle, 
and  form  by  their  junction  the  popliteal  vein. 
The  valves  of  the  deep  veins  of  the  leg  are  very 
numerous, — ten  or  twelve  sets  being  sometimes 
found  between  the  heel  and  the  knee. 

The  popliteal  vein,  thus  formed,  receives 
branches  corresponding  with  the  articular  and 
muscular  arteries ; but  its  chief  branch  is  the 
external  saphenous  vein.  In  its  course  through 
the  ham,  the  popliteal  vein  is  placed  behind  and 
to  the  outer  side  of  the  artery,  that  is  to  say,  be- 
tween it  and  the  nerve.  Thus  situated,  it  passes 
up  through  the  aperture  in  the  adductor  magnus, 
and  becomes  continuous  with  the  femoral  vein. 

The  union  of  the  veins  which  form  the  popliteal  is 
often  delayed,  and  the  lower  part  of  the  artery  is  accom- 
panied by  two  veins.  This  arrangement  in  some  cases 
extends  to  the  entire  length  of  the  artery. 

FEMORAL  VEIN. 

The  femoral  vein,  fig.  258,  k,  [v.  femoralis,  s. 
cruralis,]  extends,  like  the  artery  which  it  accom- 
panies, through  the  upper  two-thirds  of  the  thigh. 
Placed  at  first  behind  that  vessel,  it  gradually  in- 
clines inwards  and  forwards,  so  that  on  reaching 
PoLipart’s  ligament  (where  it  terminates  in  the 
iliac  vein)  it  lies  on  the  inner  side,  and  on  the  same  plane  as  the  artery, 
being  separated  from  it  only  by  a slight  partition  which  passes  from 
before  backwards,  across  the  membranous  sheath  investing  them  both. 
In  the  lower  part  of  its  course,  the  vein  receives  all  the  venous  branches 
which  accompany  the  ramifications  of  the  arteries.  In  the  upper  part, 
the  deep  femoral  vein  opens  into  it,  having  first  received  all  the  branches 
from  muscles  supplied  by  tbe  deep  femoral  artery.  Near  its  termina- 
tion the  femoral  vein  is  joined  by  the  internal  saphenous  vein,  fig.  258,  i 


The  femoral  vein  occasionally  pursues  a different  course  from  the  artery  along 
the  thigh.  Extending  upwards  from  the  popliteal  space,  the  vein  in  such  cases 
perforates  the  adductor  magnus  above  the  ordinary  position,  and  joining  with  the 
deep  femoral  vein  first  approaches  the  femoral  artery  at  the  groin.  The  same  vein 
is  now  and  then  double  in  a small  part,  or  more  rarely  in  almost  its  whole  length. 


COMMON  ILIAC  VEIN. 


27 


EXTERNAL  ILIAC  VEIN. 

The  femoral  vein,  placed  at  the  inner  side  of  the  artery,  enters  the 
abdomen  beneath  Poupart’s  ligament,  and  assumes  the  name  of  external 
iliac  vein,  fig.  258,  I,  [v.  iliaca  externa.]  This  vessel,  lying  at  first 
on  the  inner  side,  and  on  the  same  plane  with  the  external  iliac  artery, 
gradually  inclines  somewhat  behind  it  in  approaching  the  sacro-iliac 
junction,  where  it  joins  the  internal  iliac  vein,  to  form  the  common 
iliac  vein.  Near  its  commencement  at  Poupart’s  ligament,  the  ex- 
ternal iliac  vein  I'eceives  the  circumflex  iliac  and  epigastric  veins. 
It  is  not  provided  with  valves. 

INTERNAL  ILIAC  VEIN. 

The  internal  iliac  vein,  fig.  258,  m,  [v.  iliaca  interna,  s.  hypogas- 
trica.] — All  the  branches  of  the  internal  iliac  artery  are  accompanied 
by  veins,  except  the  umbilical,  whose  corresponding  vein  passes  in  the 
foetus  upwards  to  the  liver  : these  several  veins  give  rise  to  the  internal 
iliac.  The  vessel  thus  formed  lies  behind  the  corresponding  artery  in 
front  of  the  sacro-iliac  junction,  and,  after  a very  short  course  up- 
wards to  the  margin  of  the  pelvis,  joins  with  the  external  iliac  vein  to 
form  the  common  iliac.  It  returns  the  blood  from  the  organs  con- 
tained within  the  pelvis,  and  from  the  large  mass  of  muscles  which 
occupy  its  outer  surface.  The  branches  of  this  vein  follow  the  course 
of  the  arteries  derived  from  the  internal  iliac  artery,  and,  being  re- 
markable for  their  size  and  their  frequent  anastomoses  one  with  the 
other,  they  have  been  described  as  forming  a series  of  plexuses,  seve- 
rally named  from  the  organs  on  which  such  interlacement  occurs: 
thus  the  vesical,  hsemorrhoidal,  and  uterine  plexuses,  are  not  unfre- 
quently  mentioned.  No  valves  are  found  in  the  internal  iliac  vein, 
but  its  branches  are  provided  with  them. 

The  dorsal  vein  of  the  penis,  a vessel  of  considerable  size,  requires 
a special  notice.  Commencing  by  a series  of  branches  which  issue 
from  the  glans  penis,  we  find  in  the  first  instance  two,  one  at  each 
side  of  the  middle  line,  in  the  dorsal  groove  of  the  penis ; they  receive 
branches  from  the  corpus  cavernosum,  and  some  superficial  veins 
which  accompany  the  external  pudic  arteries.  Proceeding  backwards, 
they  unite  and  form  a short  trunk  which  enters  the  pelvis  beneath  the 
subpubic  ligament.  Here  it  divides  into  two  branches,  which  are 
directed  obliquely  downwards  over  the  prostate  and  neck  of  the  blad- 
der, where  they  anastomose  with  branches  of  the  vesical  veins,  form- 
ing a sort  of  plexus,  and  finally  open  into  the  internal  iliac  vein. 

COMMON  ILIAC  VEIN. 

Each  common  iliac  vein,  [v.  iliaca  communis,]  formed  by  the  con- 
fluence of  the  external  and  internal  iliac  veins,  passes  upwards;  and 
the  vein  of  the  left  side  inclines  towards  the  corresponding  vessel  of 
the  opposite  side.  Near  the  junction  of  the  fourth  with  the  fifth  lum- 
bar vertebra,  a little  to  the  right  of  the  middle  line,  the  two  common 
iliac  veins  unite  to  form  the  lower  or  ascending  vena  cava.  The  right 
vein  is  shorter  than  the  left,  and  is  nearly  vertical  in  its  direction. 
The  right  vein  is  placed  behind,  and  then  to  the  outer  side  of  its  artery. 


28 


LOWER  VENA  CAVA. 


whilst  the  left  vein  is  to  the  inner  side  of  the  left  common  iliac  artery. 
Both  pass  behind  the  right  common  iliac  artery. — These  veins  are 
destitute  of  valves. 

LOWER  VENA  CAVA. 

The  lower  vena  cava  (vena  cava  inferior,  ascendens),  fig.  258,  b,  re- 
turns the  residue  of  the  blood  circulated  by  the  abdominal  aorta.  It 
commences  at  the  junction  of  the  two  common  iliac  veins  on  the  side 
of  the  fourth  lumbar  vertebra,  and  thence  ascends  along  the  right  side 
of  the  aorta,  as  far  as  the  posterior  border  of  the  liver;  it  there  be- 
comes lodged  in  a groove  in  that  organ,  after  which  it  inclines  for- 
wards to  reach  the  opening  in  the  diaphragm  appropriated  to  it,  and, 
having  passed  through  the  pericardium,  terminates  in  the  right  auricle 
of  the  heart.  It  has  one  large  valve  at  its  entrance  into  the  auricle, 
named  the  valve  of  Eustachius.  In  its  course  it  receives  the  lumbar 
and  renal  veins;  also  the  spermatic,  capsular,  and  phrenic  veins;  and, 
finally,  the  hepatic  veins,  which,  through  the  medium  of  the  portal  sys- 
tem, return  the  blood  circulated  through  the  chylopoietic  viscera. 

The  lower  vena  cava  presents  some  occasional  deviations  from  its  ordinary 
condition,  which  may  be  briefly  noticed. 

Thus,  in  the  lower  part  of  its  course,  it  is  sometimes  placed  to  the  left  side  of 
the  aorta,  and,  after  receiving  the  left  renal  vein,  resumes  its  ordinary  position 
by  crossing  over  the  great  artery.  Less  frequently,  the  vena  cava  is  placed  alto- 
gether on  the  left  side,  and  is  continued  upwards  to  the  heart,  without  any  change 
in  its  direction;  the  thoracic  and  abdominal  viscera  being,  in  such  cases,  trans- 
posed, as  well  as  the  great  vessels. 

In  another  class  of  cases,  more  numerous  than  those  just  mentioned,  the  left 
common  iliac  vein,  instead  of  joining  the  right  in  its  usual  position,  is  connected 
with  it  only  by  a small  branch,  and  then  ascends  on  the  left  side  of  the  aorta. 
After  receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  terminates  by 
uniting  with  the  common  iliac  vein  of  the  right  side.  In  these  cases,  the  vena 
cava  inferior  can  be  said  to  e.xist  only  at  the  upper  part  of  the  abdomen,  and 
below  this  point  there  is  a vein  on  each  side  of  the  aorta. 

Lastly,  the  lower  vena  cava,  instead  of  ending  in  the  right  auricle  of  the  heart, 
has  been  seen  to  join  with  the  azygos  vein,  which  is  then  very  large ; so  that  the 
blood  from  the  lower,  as  well  as  from  the  upper  part  of  the  body,  enters  the  heart 
through  the  upper  vena  cava.  In  this  case,  the  hepatic  veins  do  not  join  the 
lower  cava,  but  end  at  once  in  the  right  auricle,  at  the  usual  place  of  termination 
of  the  great  vein.  [A  preparation,  exhibiting  this  anomalous  arrangement,  is 
preserved  in  the  Wistar  Museum.*] 

The  middle  sacral  vein,  fig.  258,  n,  taking  its  course  upwards  on 
the  front  of  the  sacrum,  opens  into  the  commencement  of  the  vena 
cava,  or  more  usually  into  the  left  common  iliac  vein. 

The  lumbar  veins,  fig.  258,  o,  commence  by  small  dorsal  branches 
in  the  muscles  of  the  back,  and  by  others  from  the  walls  of  the  abdo- 
men, where  they  communicate  with  the  epigastric  and  other  veins  in 
the  neighbourhood.  Having  reached  the  spine,  they  receive  branches 
from  the  spinal  plexuses:  they  proceed  forward  upon  the  bodies  of  the 
vertebras,  behind  the  psoas  muscle,  those  on  the  left  side  passing  be- 
hind the  aorta,  and  terminate  in  the  back  of  the  vena  cava.  Some  of 
these  veins  are  frequently  found  to  unite  into  a single  trunk  before 
their  termination. 

The  lumbar  veins  of  the  same  side  communicate  with  each  other 
by  branches  which  cross  in  front  of  the  transverse  processes.  One 
[*  Described  by  Dr.  Horner  in  the  “Journal  Acad.  Nat.  Sci.,”  vol.  i.  p.  401.  Phil.  1817.] 


PORTAL  SYSTEM  OF  VEINS. 


29 


branch  is  not  unfrequently  met  with,  called  the  ascending  lumbar  vein, 
which  connects  more  or  less  completely  the  common  iliac  vein,  the 
ilio-lumbar  and  lumbar  veins,  and  the  azygos  vein. 

The  spermatic  veins,  fig.  258,  p,‘q,  proceeding  upwards  from  the 
testicle,  and  forming  one  of  the  constituents  of  the  spermatic  cord, 
enter  the  abdomen,  and  ascend  on  the  psoas  muscles,  behind  the  peri- 
toneeum.  Below  the  abdominal  ring  the  veins  are  numerous,  branched 
and  convoluted ; they  form  a plexus,  named  the  spermatic  plexus 
(plexus  pampiniformis);  they  have  valves,"  but  still  may  be  injected  from 
above  downwards.  These  branches  gradually  unite,  and  form  a single 
vessel,  which  opens  on  the  right  side  into  the  lower  vena  cava,  and 
on  the  left  into  the  renal  vein.  The  spermatic  veins  sometimes  bifur- 
cate before  their  termination,  each  division  opening  separately;  in  this 
case,  the  veins  of  the  right  side  may  be  found  communicating  with 
the  vena  cava  and  the  renal  vein.  In  the  female,  the  ovarian  veins 
have  the  same  general  course  as  the  ovarian  afteries ; they  form  a 
plexus  near  the  ovary  (ovarian' or  pampiniform  plexus)  in  the  broad 
ligament,  and  communicate  with  the  uterine  plexus. 

Valves  exist  in  the  spermatic  veins  in  man  (Monro);  and,  in  ex- 
ceptional cases,  they  have  been  also  seen  in  the  ovarian  veins  (Theile). 

The  renal  or  emulgent  veins,  fig.  258,  r,  are  short,  but  of  very  con- 
siderable size.  That  of  the  left  side  is  longer  than  the  right,  and 
passes  generally  in  front  of  the  aorta.  They  join  the  vena  cava  at 
nearly  a right  angle.  The  renal  veins  usually  receive  branches  from 
the  suprarenal  capsules ; the  left  has  also  opening  into  it  the  spermatic 
vein  of  the  same  side. 

The  capsular  or  suprarenal  veins,  fig.  258,  s,  though  small,  are, 
proportionately  to  the  organs  from  which  they  arise,  of  considerable 
size.  On  the  right  side  thej^  usually  end  in  the  vena  cava,  and  on  the 
left  in  the  renal  or  phrenic  vein. 

The  phrenic  veins  follow  exactly  the  course  of  the  arteries  supplied 
to  the  diaphragm  by  the  abdominal  aorta. 

PORTAL  SYSTEM  OF  VEINS. 

In  the  adult,  as  well  as  in  the  fcetus,  the  veins  of  the  liver  present 
peculiarities  which  distinguish  them  from  the  rest  of  the  venous  sys- 
tem ;•  for  in  this  organ  a large  venous  trunk,  performing,  as  it  were, 
the  function  of  an  artery,  conveys  materials  from  which,  at  least  in 
great  part,  the  peculiar  secretion  of  the  organ  is  elaborated.  The 
portal  vein  (vena  portse),  for  so  is  this  large  venous  trunk  named,  has 
been  so  called  from  its  entering  the  liver  at  its  transverse  fissure, 
which  was  likened  to  a gateway,  the  small  lobes  placed  before  and 
behind  it  representing  its  pillars.  The  portal  vein  is  thus  formed : the 
veins  from  all  the  chylopoietic  viscera  unite  into  two  principal  trunks, 
named  the  splenic  and  superior  mesenteric  veins;  from  the  junction 
of  these  two  veins  results  the  vena  portae.  Having  reached  the  liver, 
the  portal  vein  again  divides  and  ramifies  in  the  substance  of  that 
gland,  so  that  it  may  be  said  to  have  two  sets  of  branches : one, 
branches  of  commencement  in  the  intestines,  and  the  other,  branches 
of  termination  in  the  liver;  both  being  connected  by  an  intermediate 

3* 


30 


PORTAL  SYSTEM  OF  VEINS. 


trunk.  Both  kinds  of  branches  are  in  all  cases  single,  and  destitute  of 
valves.  The  entire  system  of  these  veins,  from  the  intestines  to  the 
liver,  is  named  the  portal  system. 

The  splenic  vein,  fig.  263,  b,  is  a vessel  of  very  considerable  size, 
for  it  returns  the  blood  not  only  from  the  spleen,  but  also  from  the 
pancreas,  the  duodenum,  the  greater  part  of  the  stomach  and  omen- 
tum, the  descending  colon,  and  part  of  the  rectum.  It  commences 
by  five  or  six  branches,  which  issue  separately  from  the  fissure  of 
the  spleen,  but  soon  join  to  form  a single  vessel.  It  is  directed  from 
left  to  right,  embedded  in  the  substance  of  the  pancreas,  in  company 
with  the  splenic  artery,  beneath  which  it  is  placed".  On  reaching  the 
front  of  the  spine  it  joins  the  superior  mesenteric  vein,  nearly  at  a 
right  angle.  It  receives  gastric  branches  (vasa  brevia)  from  the  left 
extremity  of  the  stomach,  the  left  gastro-epiploic  vein,  c,  some  pan- 
creatic and  duodenal  branches,  and  also  the  two  following  veins, 
which  require  a more  detailed  notice: 

The  branches  of  the  inferior  mesenteric  vein,  fig.  263,  d,  correspond 
with  the  ramifications  of  the  artery  of  the  same  name.  They  com- 
mence behind  and  at  the  sides  of  the  rectum,  from  w'hich  they  ascend 
and  unite  into  a single  vessel,  near  the  sigmoid  flexure  of  the  colon. 
From  this  point  the  vein  passes  upwards  and  inwards  along  the  lum- 
bar region,  behind  the  perito- 
neum, crossing  between  the 
transverse  mesocolon  and  the 
spine;  sometimes  it  lies  farther 
to  the  left,  but  in  either  case  it 
passes  beneath  and  behind  the 
pancreas,  so  as  to  reach  the 
splenic  vein,  in  which  it  termi- 
nates. 

The  coronary  vein  of  the  sto- 
mach lies  parallel  with  the 
artery  of  the  same  name.  Its 
size  is  inconsiderable,  and  its 
direction  transverse  from  the 
cardiac  to  the  pyloric  end  of 
the  stomach,  along  the  lesser 
curvature.  On  reaching  the 
latter  point  it  turns  downwards, 
and  opens  into  the  splenic  vein, 
or  in  some  instances  into  the 
trunk  of  the  vena  portse. 

The  superior  mesenteric  vein, 
fig.  263,  e,  lies  to  the  right  side, 
and  somewhat  in  front  of  the 
artery  of  the  same  name.  The 
distribution  of  its  branches  cor- 
responds with  that  of  the  supe- 
rior mesenteric  artery,  and  it 
returns  the  blood  from  the  several  parts  supplied  by  that  vessel,  viz.. 


Fig.  263. 


VEINS  OF  THE  HEART. 


31 


from  the  small  intestine,  and  from  the  ascending  and  transverse  parts 
of  the  colon.  The  trunk  formed  by  the  union  of  its  several  branches 
inclines  upwards  and  to  the  right  side,  passing  in  front  of  the  duode- 
num and  behind  the  pancreas,  where  it  joins  with  the  splenic  vein. 

PORTAL  VEIN:  VENA  PORT.®. 

The  trunk  of  the  jportal  vein,  fig.  263,  a,  commencing  at  the  junction 
of  the  splenic  and  mesenteric  veins,  passes  upwards,  forwards,  and  a 
little  to  the  right,  to  reach  the  transverse  fissure  of  the  liver,  being 
about  three  inches  in  length.  It  is  placed  close  behind,  and  between 
the  hepatic  artery  and  the  hepatic  ducts.  It  is  surrounded  by  the  fila- 
ments of  the  hepatic  plexus  of  nerves,  together  with  numerous  lym- 
phatics. All  these  are  embedded  in  loose  cellular  tissue,  and  enclosed 
within  the  layers  of  the  gastro-hepatic  omentum.  Within  the  trans- 
verse fissure  it  is  somewhat  enlarged,  and  is  there  named  sinus  of  the 
'portal  vein.  Near  the  right  end  of  the  transverse  fissure,  the  vena 
portse  divides  into  two  branches.  That  of  the  right  side  enters  directly 
the  substance  of  the  corresponding  lobe  of  the  liver,  and  spreads  out 
into  branches,  each  of  which  is  accompanied  by  a branch  of  the 
hepatic  artery  and  of  the  hepatic  duct.  The  left  branch,  which  is 
smaller,  but  necessarily  longer,  passes  across  to  gain  the  left  end  of 
the  transverse  fissure,  where  it  enters  the  liver  and  ramifies  like  the 
preceding  branch.  The  blood  conveyed  to  the  liver  by  the  branches 
of  the  portal  vein  is  collected  again  and  returned  into  the  current  of 
the  circulation  by  the  hepatic  veins. 

The  hepatic  veins,  fig.  263,  t,  commence  in  the  capillary  termina- 
tions of  the  vena  portse.  Their  branches  gradually  unite  and  become 
large  as  they  pass  backwards  and  upwards,  towards  ihe  back  part  of 
the  liver,  where  the  lower  vena  cava  passes  in  a groove  behind  that 
organ.  At  this  point  they  all  end  in  the  vena  cava,  passing  obliquely 
into  that  vein.  There  are  usually  three  sets  of  hepatic  veins  proceed- 
ing to  this  common  point ; those  from  the  right  and  left  lobes  being 
oblique  in  their  direction,  those  from  the  middle  of  the  liver  and  the 
lobule  of  Spigelius  having  an  intermediate  position  and  course. 

The  hepatic  veins  run  singly,  and  have  no  companion  arteries. 
The  branches  of  the  hepatic  arteries  ramify  in  the  liver  along  with 
the  portal  veins.  The  hepatic  veins  have  no  Valves ; but,  owing  to 
their  oblique  entrance  into  the  vena  cava,  a semilunar  fold  is  seen  at 
the  lower  border  of  the  orifice  of  each  vein. 

The  hepatic  veins  sometimes,  though  rarely,  enter  at  once  into  the  auricle  of 
the  heart — ^the  vena  cava  inferior,  in  these  cases,  joining  the  azygos  vein. 

In  a remarkable  case,  observed  by  Rothe,*  one  of  the  hepatic  veins  ended,  not 
in  the  lower  cava,  nor  in  the  right  auricle,  but  in  the  right  ventricle  of  the  heart, 
its  orifice  being  guarded  by  valves. 

VEINS  OF  THE  HEART. 

The  veins  of  the  heart  {cardiac  veins)  are  recognised  as  four  in 
number,  and  named  according  to  their  relative  size.  They  are  all 
single  veins,  and  have  no  valves  in  their  course. 

* Act.  Acad.  Joseph.  Med.-Chir.  Vindobonensis,  t.  i.  p.  233,  tab.  5.  Vindobonae,  1788. 


32 


VEINS  OF  THE  HEART. 


The  great  cardiac  vein  (vena  cordis  magna)  is  a vessel  of  consi- 
derable size,  and  from  the  way  in  which  it  coils  round  the  left  side  of 
the  base  of  the  heart,  or  rather  of  the  ventricle,  it  may  be  named 
“ coronary.”  Its  chief  branch  runs  along  the  groove  upon  the  fore 
part  of  the  heart,  corresponding  with  the  septum  of  the  ventricles. 
Commencing  at  the  apex  of  the  heart,  it  gradually  increases  in  size  as 
it  approaches  the  base  of  the  ventricles,  and  then  inclining  backwards 
and  to  the  left  side,  runs  in  the  groove  between  the  left  auricle  and 
ventricle,  and  prolonging  its  course  a few  lines  beyond  this  groove, 
opens  into  the  right  auricle,  close  to  the  interauricular  septum.  In  this 
course  it  receives  branches  from  the  ventricles,  especially  from  the 
left,  and  also  from  the  left  auricle ; and  when  it  passes  by  the  thick 
margin  of  the  left  ventricle,  it  receives  a vein  of  some  size,  which  as- 
cends to  join  it.  At  the  entrance  of  this  vein  into  the  auricle,  is  situa- 
ted a semilunar  fold  of  the  lining  membrane,  or  valve,  named  valvula 
Tkebesii. 

The  middle  cardiac  vein  (vena  cordis  media). — The  term  “ coro- 
nary” cannot  be  applied  to  this  vessel,  as  its  direction  is  straight, 
along  the  groove  between  the  ventricles  upon  the  posterior  surface  of 
the  heart.  It  commences  by  small  branches  at  the  apex  of  the  heart, 
which  communicate  with  those  of  the  preceding  vein,  then  ascends  to 
the  base,  receiving  branches  from  the  substance  of  both  ventricles,  and 
opens  into  the  great  vein  near  its  termination. 

The  small  or  anterior  cardiac  veins  (venae  cordis  parvae)  are  seve- 
I'al  small  branches,  which  commence  upon  the  anterior  surface  of  the 
right  ventricle,  and  pass  upwards  and  outwards,  opening  separately 
into  the  right  auricle,  after  having  crossed  over  the  groove  between  it 
and  the  ventricle. 

The  smallest  cardiac  veins  (venae  cordis  minimas). — Under  this 
name  are  included  numerous  minute  vessels,  the  orifices  of  which  are 
observable  on  the  inner  surface  of  the  right  auricle.  From  having 
been  noticed  by  an  old  anatomist,  Thebesius,  these  openings  are  called 
foramina  Tliebesii.  Some  of  these  openings  do  not  appear  to  be 
mouths  of  veins,  but  only  of  small  depressions  in  the  wall  of  the 
auricle. 


LYMPHATIC  SYSTEM. 


THE  LYMPH  AND  CHYLE. 

A TRANSPARENT,  and  nearly  colourless  fluid,  named  “lymph,”  is  con- 
veyed into  the  blood,  by  a set  of  vessels  distinct  from  those  of  the 
sanguiferous  system.  These  vessels,  which  are  named  “ lymphatics” 
from  the  nature  of  their  contents,  and  “ absorbents”  on  account  of 
their  reputed  office,  take  their  rise  in  neai’ly  all  parts  of  the  body,  and 
after  a longer  or  shorter  course,  discharge  themselves  into  the  great 
veins  of  the  neck  ; the  greater  number  of  them  previously  joining  into 
a main  trunk,  named  the  thoracic  duct, — a long  narrow  vessel  which 
rises  up  in  front  of  the  vertebrae,  and  opens  into  the  veins  on  the  left 
side  of  the  neck,  at  the  angle  of  union  of  the  subclavian  and  internal 
jugular : whilst  the  remaining  lymphatics  terminate  in  the  correspond- 
ing veins  of  the  right  side.  The  absorbents  of  the  small  intestine 
carry  an  opaque  white  liquid,  named  “ chyle,”  which  they  absorb 
from  the  food  as  it  passes  along  the  alimentary  canal ; and,  on  account 
of  the  milky  aspect  of  their  contents,  they  have  been  called  the  “ lacteal 
vessels.”  But  in  thus  distinguishing  these  vessels  by  name,  it  must  be 
remembered,  that  they  differ  from  the  rest  of  the  absorbents  only  in 
the  nature  of  the  matters  which  they  convey ; and  that  this  difference 
holds  good  only  while  digestion  is  going  on  : for  at  other  times  the 
lacteals  contain  a clear  fluid,  not  to  be  distinguished  from  lymph. 
The  lacteals  enter  the  commencement  of  the  thoracic  duct,  and  the 
chyle,  mingling  with  the  lymph  derived  from  the  lower  part  of  the 
body,  is  conveyed  along  that  canal  into  the  blood. 

Both  lacteals  and  lymphatics,  in  proceeding  to  their  destination,  pass 
through  certain  small,  solid  and  vascular  bodies,  named  lymphatic 
glands,  in  which  they  are  in  some  degree  modified  in  structure  and 
arrangement,  as  will  be  afterwards  described  ; so  that  both  the  chyle 
and  lymph  are  sent  through  these  glands  before  being  mixed  with  the 
blood. 

This  much  having  been  explained  to  render  intelligible  what  follows, 
we  may  now  consider  the  lymph  and  the  chyle,  which,  as  will  be 
seen,  are  intimately  related  to  the  blood. 


LYMPH. 

The  lymph  may  be  procured  free  from  admixture  of  chyle,  and  in 
quantity  sufficient  for  examination,  from  the  larger  lymphatic  vessels 
of  the  horse  or  ass.  It  may  also  be  obtained,  by  opening  the  thoracic 
duct  of  an  animal  that  has  fasted  for  some  time  before  being  killed.  It 
is  a thin  fluid,  transparent  and  colourless,  or  occasionally  of  a pale 


34 


LYMPH. 


yellow  hue ; its  taste  is  saline,  its  smell  faint  and  scarcely  perceptible, 
and  its  reaction  alkaline.  Sometimes  the  lymph  has  a decided  red 
tint,  of  greater  or  less  depth,  which  becomes  brighter  on  exposure  to 
the  air.  This  redness  is  due  to  the  presence  of  coloured  corpuscles, 
like  those  of  the  blood  : and  it  has  been  supposed,  that  such  corpuscles 
exist  naturally  in  the  lymph,  in  greater  or  less  quantity;  but  Mr.  Lane,* 
who  has  lately  investigated  the  point,  concludes,  that  they  are  intro- 
duced into  the  lymphatic  vessels  accidentally;  he.adduces  an  experi- 
ment to  show,  that  when  an  incision  is  made  into  a part,  the  blood 
will  very  readily  enter  the  lymphatics  which  are  laid  open,  and  pass 
along  into  larger  trunks  ; and  he  conceives,  that  in  this  way  blood  is 
conveyed  into  the  thoracic  duct,  or  any  other  large  vessel,  exposed  as 
usual  by  incision  immediately  after  the  animal  is  killed. 

The  lymph,  when  examined  with  the  microscope,  is  seen  to  consist 
of  a clear  liquid,  with  corpuscles  floating  in  it.  These  “ lymph  cor- 
puscles,” or  lymph  globules,  agree  entirely  in  their  characters  with 
the  pale  corpuscles  of  the  blood,  which  have  been  already  described. 
Occasionally,  smaller  particles  are  found  in  the  lymph;  also,  but  more 
rarely,  a few  oil  globules  of  various  sizes,  as  well  as  red  blood  cor- 
puscles, the  presence  of  which  has  just  been  referred  to. 

The  liquid  part  (lymph-plasma),  bears  a strong  resemblance  in  its 
physical  and  chemical  constitution  to  the  plasma  of  the  blood:  and, 
accordingly,  lymph  fresh  drawn  from  the  vessels  coagulates  after  a 
few  minutes’  exposure,  and  separates  after  a time  into  clot  and  serum. 
This  change  is  owing  to  the  solidiflcation  of  the  flbrin  contained  in  the 
lymph-plasma,  and  in  this  process  most  of  the  corpuscles  are  entangled 
in  the  coagulum.  The  serum,  like  the  corresponding  part  of  the  blood, 
consists  of  water,  albumen,  extractive  matters,  fatty  matters  in  very 
sparing  quantity,  and  salts. 

Human  lymph  has  been  obtained  fresh  from  the  living  body  in  two 
instances,  in  which  a lymphatic  vessel  had  been  accidentally  opened 
by  a wound.  It  has  been  found  to  agree  in  all  material  points  with 
the  lymph  of  quadrupeds.  Its  speciflc  gravity,  in  the  case  examined 
by  Marchand  and  Colberg,  was  1037. 

The  following  analyses  exhibit  the  proportion  of  the  different  ingredients;  but 
it  must  be  explained,  that  the  amount  of  the  corpuscles  cannot  be  separately 
given,  the  greater  part  of  them  being  included  in  the  clot  and  reckoned  as  fibrin. 

Lymph  of  the  ass  from  the  lymphatics  of  the  posterior  limb,  (by  Dr.  G.  0.  Rees)  :f — 


Water  ........  96'536 

Albuminous  matter  ......  1200 

Fibrinous  matter  . . . . . . 0T20 

Extractive  matter  soluble  in  water  and  alcohol  . . 0-240 

Extractive  matter  soluble  in  water  only  . . . 1-319 

Fatty  matter  ......  a trace 


Salts,  viz. — Alkaline,  chloride,  sulphate,  and  carbonate,  with 
traces  of  alkaline  phosphate,  oxide  of  iron 


100- 

*■  Cycloptedia  of  Anatomy,  art.  Lymphatic  System, 
t Medical  Gazette,  Jan.  1,  1841. 


CHYLE. 


35 


Lymph  from  the  lumbar  lymphatics  of  the  horse  (Gmelin) : — 


Water  ...... 

96-10 

Dried  clot  (fibrin,  with  corpuscles)  . 
Dried  serum,  3-65,  viz. 

0-25 

Albumen  ..... 

2-76 

Extractive  matter  soluble  in  alcohol  (osmazome),  with 
alkaline  chloride,  and  acetate 
Extractive  matter  soluble  in  water  only,  with  alkaline 
carbonate,  phosphate,  and  chloride 


100- 

Human  lymph  from  a lymphatic  vessel  on  the  instep  of  the  foot,  (Marchand  and 


Colb  erg) : — 

Water  . . . . . . . . 96-926 

Fibrin  .......  0-520 

Albumen . . . . . . . . 0-434 

Osmazome  (and  loss)  .....  0 312 

Fatty  matters  .......  0-264 

Salts,  viz. — Chlorides  of  sodium  and  potassium,  alkaline  car- ) 

bonate,  and  lactate  ] sulphate  and  phosphate  of  lime,  and  > 1-544 

oxide  of  iron  . . . . . . \ 


100- 

The  proportion  of  fibrin  has  been  supposed  to  increase  as  the  lymph  approaches 
the  thoracic  duct;  thus,  from  the  lumbar  lymphatics  of  a fasting  horse,  Gmelin 
obtained  0-25  per  cent,  of  dry  coagulum,  and  from  that  of  the  thoracic  duct  of  the 
same  animal,  0-42  per  cent.  As  regards  the  amount  of  albumen,  Leuret  and 
Lassaigne  assign  it  at  5-7  per  cent.,  but  this  includes  the  extractive  matter;  on  the 
other  hand,  Berzelius  suspects,  that  the  method  followed  by  Marchand  and  Col- 
berg  leads  to  too  lo-yv  an  estimate;  but  there  seems  reason  to  think  that,  apart 
from  all  error,  the  proportion  of  .this  ingredient  will  be  found  to  vary. 

CHYLE. 

The  chyle  of  man  and  mammiferous  animals,  is  an  opaque,  -white 
fluid,  like  milk,  with  a faint  odour  and  saltish  taste,  slightly  alkaline, 
or  altogether  neutral  in  its  reaction.  It  has  often  a decided  red  tint, 
especially  when  taken  from  the  thoracic  duct.  This  colour,  which  is 
heightened  by  exposure  to  air,  is  owing  to  the  presence  of  blood-cor- 
puscles, and  may  be  explained  in  the  same  way  as  the  occasional  red 
colour  of  lymph. 

Like  blood  and  lymph,  both  of  which  fluids  it  greatly  resembles  in 
constitution,  the  chyle  consists  of  a liquid  holding  small  particles  in 
suspension.  These  particles  are,  1.  Chyle  corpuscles,  or  chyle  globules, 
precisely  like  the  lymph  globules  and  pale  blood-corpuscles  already 
described.  2.  Molecules,  of  extremely  minute,  but  remarkably  uniform 
size,  probably  between  of  inch  in  diameter.  These 

abound  in  the  fluid,  and  form  an  opaque  white  molecular  matter  dif- 
fused in  it,  which  Mr.  Gulliver  has  named  the  molecular  base  of  the 
chyle.  The  addition  of  ether  instantly  dissolves  this  matter,  and  ren- 
ders the  chyle  nearly,  but  not  quite,  transparent;  whence  it  maybe 
inferred,  that  the  molecules  are  minute  particles  of  fatty  matter,  and 
probably  the  chief  cause  of  the  opacity  and  whiteness  of  the  chyle. 
They  exhibit  the  usual  tremulous  movements  common  to  the  molecules 
of  many  other  substances.  3.  Oil  globules  ; these  are  of  various  sizes, 


0-69 

0-20 


36 


CHYLE. 


but  much  larger  than  the  molecules  above  described,  and  are  often 
found  in  the  chyle  in  considerable  numbers.  4.  Minute  spherules 
(Gulliver),  from  2?Wo  to  yoVo  of  an  inch  in  diameter;  probably  of  an 
albuminous  nature,  and  distinguished  from  the  fatty  molecules  by  iheir 
varying  magnitude  and  their  insolubility  in  ether. 

The  plasma,  or  liquid  part  of  the  chyle,  contains  fibrin,  so  that  the 
chyle  coagulates  on  being  drawn  from  the  vessels,  and  nearly  all  the 
chyle  corpuscles,  with  part  of  the  molecular  base,  are  involved  in  the 
clot.  The  serum  which  remains,  resembles  in  composition  the  serum 
of  lymph  ; the  most  notable  difference  between  them  being,  the  larger 
proportion  of  fatty  matter  contained  in  the  former. 

Subjoined  is  an  analysis,  by  Dr.  Rees,  of  chyle  taken  from  the  lacteals  of  an  ass 
after  the  fluid  had  passed  the  mesenteric  glands,  but  before  it  entered  the  thora- 
cic duct. 

Water 90-237 

Albuminous  matter  .......  3 516 

Fibrinous  matter  ........  0 370 

Extractive  matter  soluble  in  water  and  alcohol  . . O' 3 32 

Extractive  matter  soluble  in  water  only  . . . . 1-233 

Fatty  matter 3-601 

Alkaline  chloride,  sulphate  and  carbonate,  with  traces  ) 

of  phosphate,  oxide  of  iron J 0-711 


100- 

Dr.  Rees  ascribes  the  whiteness  of  the  chyle  principally  to  a peculiar  substance 
insoluble  in  alcohol  and  in  ether,  but  miscible  with  water,  which  he  considers 
analogous  to  the  mucoid  matter  obtained  from  the  saliva.  Others  attribute  the 
whiteness  chiefly  to  the  fatty  ingredients,  and  this  view  accords  with  the  fact, 
that  food  containing  much  fat  yields  a remarkably  white  and  opaque  chyle. 

The  chyle,  when  taken  from  the  lacteal  vessels  before  they  have  reached  the 
glands,  is  generally  found  to  coagulate  less  firmly  than  in  a more  advanced  stage 
of  its  progress;  and  it  has  been  observed,  that  after  such  feeble  coagulation,  it 
will  sometimes  spontaneously  return  to  the  liquid  state.  In  like  manner  the 
lymph,  before  passing  the  lymphatic  glands,  occasionally  exhibits  the  same  weak 
coagulation  and  tendency  to  subsequent  liquefaction ; but  Mr.  Lane  justly  re- 
marks, that  the  lymph  does  not  differ  in  coagulability  in  the  different  stages  of  its 
progress  so  decidedly  and  so  generally  as  has  been  sometimes  alleged;  and  this 
observation  accords  with  the  statement  of  Mr.  Hewson  on  the  same  point.* 

Dr.  Rees  has  examined  the  fluid  contained  in  the  thoracic  duct  of  the  human 
subject.  It  was  obtained  from  the  body  of  a criminal  an  hour  and  a half  after 
execution,  and,  from  the  small  quantity  of  food  taken  for  some  hours  before 
death,  it  must  have  consisted  principally  of  lymph.  It  had  a milky  hue  with  a 
slight  tinge  of  buff;  part  of  it  coagulated  feebly  on  cooling:  its  specific  gravity 
was  1024.  Its  analysis,  compared  with  that  of  the  chyle  of  the  ass,  shows  less 
water,  more  albumen,  less  aqueous  extractive,  and  a great  deal  less  fat.f 

FORMATION  OF  THE  CORPUSCLES  OF  THE  LYMPH  AND  CHYLE. 

Very  little  is  known  concerning  this  process.  No  absorbent  or  open  orifices 
having  been  discovered  in  the  lymphatics,  it  can  scarcely  be  supposed,  that  the 
lymph  globules  are  introduced  into  the  vessels  ready  formed,  unless  it  be  ima- 
gined that  the  commencing  lymphatics  are  destitute  of  membranous  parietes, 
and  of  this  there  is  no  evidence.  The  corpuscles  are,  therefore,  most  probably 
developed  as  cells  within  the  lymphatic  vessels,  and  there  are  various  modes  in 
which  such  a production  of  cells  might  be  conceived  to  take  place.  Thus,  ac- 
cording to  one  view,  the  lymph  globules  or  cells  are  developed  from  nuclei  in 
the  liquid  part  of  the  lymph,  which  serves  as  a blastema.  In  this  case  the  nuclei 

* Experimental  Inquiries,  part  ii.  p.  105.  t Phil.  Trans.  1842. 


LYMPHATIC  VESSELS. 


37 


may  be  formed  by  aggregation  of  matter  round  nucleoli,  which  again  may  be 
derived  as  germs  from  other  cells;  or,  as  Henle  is  disposed  to  think,  two  or  more 
fat  particles  may  unite  to  form  a nucleus  in  the  way  already  described  (vol.  i.  p.  57). 
Upon  another  view  it  may  be  conceived  that  the  lymph  corpuscles  are  formed  on 
the  inner  surface  of  the  walls  of  their  containing  vessels,  as  epithelium  or  mucous 
corpuscles  are  produced  on  their  supporting  membrane;  and  that  this  process 
may  be  connected  with  the  absorption  of  lymph  into  the  vessels,,  in  like  manner 
as  secretion  into  a gland-duct,  or  other  receptacle,  is  accompanied  by  the  forma- 
tion and  detachment  of  cells,  as  will  be  afterwards  explained. 

The  chyle  globules,  possessing  the  same  characters  as  those  of  the  lymph,  are 
most  probably  formed  in  the  same  -way.  They  are  found  in  all  parts  of  the  chy- 
liferous  system,  but  most  abundantly  in  chyle  obtained  from  the  mesenteric 
glands;*  and  this  fact  readily  falls  in  with  the  hypothesis,  that  the  corpuscles,  or 
their  germs,  are  thrown  off  from  the  inner  surface  of  the  vessels. 


LYMPHATIC  VESSELS. 

Under  this  head  we  include  not  only  the  vessels  specially  called 
lymphatics,  together  with  the  glands  belonging  to  them,  but  also  those 
named  lacteal  or  chyliferous,  which  form  part  of  the  same  system, 
and  differ  in  no  respect  from  the  former,  save  that  they  not  only  carry 
lymph  like  the  rest,  but  are  also  employed  to  take  up  the  chyle  from 
the  intestines  during  the  process  of  digestion  and  convey  it  into  the 
blood.  An  introductory  outline  of  the  absorbent  system  has  already 
been  given  at  page  33. 

A system  of  lymphatic  vessels  is  superadded  to  the  sanguiferous 
in  all  classes  of  vertebrated  animals,  but  such  is  not  the  case  in  the 
invertebrata  ; in  many  of  these,  it  is  true,  the  sanguiferous  vessels 
convey  a colourless  or  nearly  colourless  blood,  but  no  additional  class 
of  vessels  is  provided  for  conveying  lymph  or  chyle,  at  least  none 
such  has  hitherto  been  detected. 

Distribution. — In  man  and  those  animals  in  which  they  are  present, 
the  lymphatic  vessels  are  found  in  nearly  all  the  textui’es  and  organs 
which  receive  blood  ; the  exceptions  are  few,  and  with  the  progress  of 
discovery  may  yet  possibly  disappear. 

Lymphatics  have  not  as  yet  been  traced  in  the  substance  of  the 
brain  and  spinal  cord,  though  they  exist  in  the  membranous  envelopes 
of  these  parts ; nor  have  they  been  detected  within  the  eyeball,  or  in 
the  placenta  and  foetal  envelopes.  It  is  true  that  some  anatomists  have 
succeeded  in  injecting  what  they  conceive  to  be  plexuses  of  lymphatic 
vessels  in  the  cornea  of  the  eye  and  in  the  umbilical  cord,  but  it  has 
not  been  satisfactorily  shown  that  the  injection  in  these  cases  had 
really  passed  into  lymphatics.  I have  distinctly  seen  lymphatic  ves- 
sels, distended  with  their  own  lymph,  on  the  surface  of  an  eye  which 
had  repeatedly  suffered  from  chronic  inflammation  ; but  in  this  case 
the  vessels  appeared  to  be  in  or  immediately  beneath  the  conjunctival 
membrane. 

In  the  different  regions  of  the  body,  and  in  the  several  internal  vis- 

* Gulliver’s  Supplement  to  Gerber’s  Anatomy,  p.  92. 

VOL.  II.  4 


38 


LYMPHATIC  VESSELS. 


Fig.  264. 


cera,  the  lymphatics  are  arranged  in  a superficial  and  a deep  set.  The 
former  run  underneath  the  skin  or  under  the  membranous  coats  imme- 
diately enveloping  the  organs  in  which  they  are  found ; the  latter  usu- 
ally accompany  the  deep-seated  blood-vessels.  The  principal  lym- 
phatic vessels  of  a part  exceed  the  veins  in  number,  but  fall  short  of 
them  in  size;  they  also  anastomose  or  intercommunicate  much  more 
frequently  than  the  veins  alongside  of  which  they  run. 

Origin. — This  may  be  either  superficial  or  deep;  that  is,  the  lym- 
phatics may  arise  immediately  underneath  free  surfaces,  both  external 
and  internal,  as  for  example  those  of  the  skin  and  mucous  membranes, 
or  deeply  in  the  substance  of  organs. 

In  the  superficial  mode  of  origin,  the  lym- 
phatics most  generally  arise  in  form  of  net- 
works or  plexuses  out  of  which  single  vessels 
emerge  at  various  points  and  proceed  directly 
to  lymphatic  glands  or  to  join  larger  lym- 
phatic trunks.  These  plexuses  of  origin  for 
the  most  part  consist  of  several  strata,  be- 
coming, finer  as  they  approach  the  surface,  in 
respect  both  of  the  calibre  of  the  vessels  and 
the  closeness  of  their  reticulation.  This  is 
Lymphatic  vessels  of  the  skin  shown  in  the  adjoining  figure  (264),  which  is 

of  the  breast  injected,— after  {q  represent  the  lymphatic  plexuses  of 

Brescliet.— a,  superhcial,  and  6.  I v 1 , , 

deeper  plexus,  c.  A lymphatic  the  skin.  i3ut  even  the  most  Superficial  and 

axiTlar  "lands  '’’®  finest  network  is  composed  of  vessels  which 

' ' are  larger  than  the  sanguiferous  capillaries. 

They  do  not  open  on  the  surface,  as  was  at  one  time  supposed,  and 
the  fluids  which  they  imbibe  must  pass  into  them  by  transudation. 


In  some  situations  the  plexuses  of  origin  have  much  the  appearance  of  strata 
of  intercommunicating  cells,  and  accordingly  the  lymphatics  have  been  some- 
times described  as  arising  from  small  cellular  cavities.  A characteristic  example 
of  the  appearance  referred  to  is  afforded  by  the  intestine  of  the  turtle,  after  its 
lymphatics  have  been  injected  with  mercury ; these  vessels  are  then  seen  to 
emerge  from  what  has  all  the  appearance  of  a dense  stratum  of  small  rounded 
cells  filled  with  mercury  and  lying  beneath  the  surface  of  the  mucous  coat.  This 
appearance  is,  however,  to  he  regarded  as  in  reality  produced  by  the  short  dis- 
tended branches  of  a very  close  lymphatic  network,  and  transitions  are  accord- 
ingly met  with  between  this  and  the  more  usual  and  regular  forms. 

But  the  plexiform  mode  of  origin,  though  perhaps  the  most  common,  is  not 
universal.  According  to  recent  observations  by  Kdlliker,  the  cutaneous  lym- 
phatics in  the  tail  of  batrachian  larvae  branch  out  in  an  arborescent  manner,  and 
do  not  unite  into  a network ; their  ultimate  branches,  or,  to  speak,  perhaps,  more 
properly,  their  commencing  radicles,  have  free  but  closed  ends,  not  dilated,  but 
running  out  into  fine  points.  Again,  the  origin  of  the  lacteals  in  the  intestinal 
villi  is  by  many  held  to  be  peculiar.  It  was  supposed  by  some  that  they  began 
by  open  mouths  on  the  surface  of  the  villi.  Lieberkiihn  conceived  that  there 
was  a single  opening  on  the  summit  of  each  villus  leading  to  a cellular  cavity 
within,  which  he  named  “ ampulla,”  and  from  which  a lacteal  vessel  proceeded. 
Cruikshank,  from  what  he  saw  in  examining  the  human  villi  when  they  were 
distended  with  chyle,  was  led  to  believe  that  each  of  these  processes  had  on  its 
surface  several  orifices  of  commencing  lacteals.  Others,  denying  the  reality  of 
these  apparent  openings,  still  differ  in  opinion  as  to  the  arrangement  of  the  lac- 
teal vessels  within  the  villi.  Some,  following  the  opinion  of  Mascagni  and 
Meckel,  describe  the  commencing  lacteals  of  a villus  as  arranged  in  a plexus 


LYMPHATIC  VESSELS. 


39 


like  its  blood-vessels ; and  this  view,  which  is  also  supported  by  recent  observa- 
tions of  E.  H.  Weber,  appears  to  be  the  most  probable.  Krause  describes  and 
figures  a lacteal  taking  its  rise  in  a villus  by  several  smaller  branches,  of  which 
some  appear  to  commence  by  a free  extremity,  and  others  join  in  a plexus. 
Henle,  on  the  other  hand,  found  in  each  of  the  villi  only  a single  lacteal  branch 
with  a blind  dilated  extremity,  and  this  view,  or  one  substantially  the  same,  is 
supported  by  Herbst.* 

When  lymphatics  arise  deeply,  their  origin  is  hidden  from  view, 
and  the  precise  mode  in  which  it  takes  place  is  not  known.  There  is, 
however,  no  good  ground  for  supposing  that  it  differs  in  any  essential 
point  from  what  is  observed  in  the  more  obvious  cases  already  re- 
ferred to. 

It  has  been  sometimes  maintained  that  the  lymphatics  of  glandular  organs 
communicate  at  their  origin  with  the  ducts ; but,  although  it  is  no  uncommon 
thing  for  matters  artificially  injected  into  the  ducts  of  glands,  as,  for  instance, 
those  of  the  liver  and  testicle,  to  pass  into  the  lymphatics,  a careful  examination 
of  such  cases  leads  to  the  conclusion  that  the  injected  material  does  not  find  its 
way  from  the  ducts  into  the  lymphatics  by  any  naturally  existing  communication, 
but  by  accidental  rupture  of  contiguous  branches  of  the  two  classes  of  vessels. 
It  seems,  probable,  also,  that  the  communications  often  held  to  exist  between 
the  commencing  lymphatics,  both  superficial , and  deep,  and  capiUary  blood- 
vessels, have  no  better  foundation,  and  that  the  passage  of  injection  here  also 
relied  on  as  evidence,  is  to  be  accounted  for  in  the  same  way.  A fact  mentioned 
by  Kolliker ' throws  light  on  these  aUeged  communications  with  sanguiferous 
capillaries.  In  investigating  the  lymphatics  of  the  tadpole's  tail  with  the  micro- 
scope, that  observer  not  unfiequently  noticed  that  blood  corpuscles  got  into  the 
lymphatics  from  the  small  blood-vessels,  and  he  was  able  to  recognise  in  the 
living  animal  the  communications  by  which  they  passed.  At  first  he  looked  on 
these  communications  as  natural,  but,  after  repeated  and  careful  investigations, 
he  satisfied  himself  that  they  were  produced  accidentally  by  contusions  or  some 
other  injuries  inflicted  on  the  parts. 

Structure. — The  lymphatic  vessels  have  much  thinner  coats  than 
the  arteries  or  veins,  so  thin  and  transparent  indeed  that  the  contained 
fluid  can  be  readily  seen  through  them.  Kolliker  describes  the  fine 
lymphatics  which  he  saw  in  the  tail  of  batrachian  larvee  as  consisting 
of  a simple  homogeneous  membrane  like  that  of  the  sanguiferous 
capillaries,  only  still  more  delicate,  and  like  that  also  presenting  nuclei- 
form  corpuscles,  which  were  enveloped  in  groups  of  fine  granules. 
The  vessels  w'ere  jagged  or  serrated  along  both  sides  with  sinuosities 
and  pointed  denticulations.  According  to  Henle,  the  commencing 
lacteals  in  the  intestinal  villi  consist  also  of  a simple  membrane  with 
elongated  nucleiform  corpuscles  lying  in  a longitudinal  direction. 

The  medium-sized  and  larger  lymphatics,  as  well  as  the  thoracic 
duct,  are  admitted  by  all  anatomists  to  have  at  least  two  coats,  and 
some  assign  three,  besides  an  epithelium  on  the  inner  surface.  Mr. 
Lane  describes  three,  namely,  an  internal,  which  is  lined  by  the  epi- 
thelium, a middle  or  fibrous,  and  an  external,  analogous  to  the  external 
or  cellular  coat  of  the  blood-vessels.  The  inner  tunic  is  thin  and 
transparent,  also  extensible  and  elastic,  but  less  so  than  the  other 
coats,  for  it  is  the  first  to  give  way  when  the  vessel  is  unduly  dis- 
tended; its  internal  surface  is  covered  with  a simple  layer  of  scaly 

* Das  Lymphgefasssystem  und  seine  Verrichtuiigen.  Getting.  1844. 


40 


LYMPHATIC  VESSELS. 


epithelium,  as  in  the  blood-vessels.  The  middle  or  fibrous  coat,  is 
very  extensible  and  elastic.  It  consists,  according  to  Mr.  Lane,  of 
longitudinal  fibres,  having  the  anatomical  characters  of  the  plain,  in- 
voluntary muscular  fibres,  freely  mixed  with  fibres  of  cellular  tissue. 
Ilerbst  describes  two  layers  of  plain  muscular  fibres  in  the  middle 
tunic,  but  Mr.  Lane  states,  that,  although  a few  may  be  distinguished 
next  to  the  inner  coat,  taking  a transverse,  and  others  an  oblique  di- 
rection, the  great  majority  run  longitudinally.  The  external  or  cellu- 
lar coat  resembles  that  of  the  blood-vessels,  like  which  it  possesses 
considerable  extensibility  and  elasticity,  and  is  composed  of  interlaced 
fasciculi  of  areolar  tissue,  mixed  with  some  elastic  fibres. 

The  lymphatics  receive  vasa  vasorum,  which  ramify  in  their  outer 
and  middle  coats:  nerves  distributed  to  them  have  not  yet  been  dis- 
covered, although  their  probable  existence  has  been  inferred  on  physi- 
ological grounds. 

Vital  properties . — That  the  lymphatics  are  endowed  with,  vital  contractility  is 
shown  by  the  effect  of  mechanical  irritation  applied  to  the  thoracic  duct,  as  well 
as  by  the  general  shrinking  and  emptying  of  the  lacteal  and  lymphatic  vessels  on 
their  exposure  to  the  contact  of  cold  air,  in  the  bodies  of  animals  opened  imme- 
diately after  death. 

Valves. — The  lymphatic  and  lacteal  vessels  are  furnished  with 
valves  serving  the  same  office  as  those  of  the  veins,  and  for  the  most 
part  constructed  after  the  same  fashion.  They  generally  consist  of 
two  semilunar  folds  arranged  in  the  same  way  as  in  the  valves  of 
veins  already  described,  but  deviations  from  the  usual  structure  here 
and  there  occur.  Thus  Mr.  Kane  has  observed  some  valves  in  which 
the  planes  of  the  semilunar  flaps  were  directed  not  obliquely  but  trans- 
versely across  the  vessel ; an  arrangement  calculated  to  impede  the 
flow  of  fluid  in  both  directions,  but  not  completely  to  intercept  it  in 
either.  In  others,  described  by  the  same  authority,  the  two  folds, 
placed  transversely  as  before,  were  coalesced  at  one  end,  so  as  to 
represent  a transverse  septum  with  an  incomplete  transverse  slit.  In 
a third  variety,  he  found  the  valve  formed  of  a circular  fold  corre- 
sponding with  a constriction  outside,  and  probably  containing  circular 
contractile  fibres  capable  of  completely  closing  the  tube. 

Valves  are  not  present  in  all  lymphatics,  but  where  they  exist  they 
follow  one  another  at  much  shorter  intervals  than  those  of  the  veins, 
and  give  to  the  lymphatics,  when  much  distended,  a beaded  or  jointed 
appearance.  Valves  are  placed  at  the  entrance  of  the  lymphatic 
trunks  into  the  great  veins  of  the  neck.  They  are  wanting  in  the 
reticularly  arranged  vessels  which  compose  the  plexuses  of  origin 
already  spoken  of;  so  that  mercury  injected  into  one  of  these  vessels 
runs  in  all  directions  so  as  to  fill  a greater  or  less  extent  of  the  plexus, 
and  passes  along  the  separate  vessels  which  issue  from  it. 

The  lymphatics  of  fish  and  naked  amphibia  are,  generally  speaking, 
destitute  of  valves,  and  may  therefore  be  injected  from  the  trunks  ; in 
the  turtle  a few  valves  are  seen  on  the  larger  lacteals  which  pass 
along  the  mesentery,  but  none  on  those  upon  the  coats  of  the  intestine; 
and  valves  are  much  less  numerous  in  the  lymphatics  and  lacteals  of 
birds  than  in  those  of  mammiferous  animals. 


LYMPHATIC  GLANDS. 


41 


Ahsorhent  or  lym'phatic  glands,  named  also  conglobate  glands,  and 
by  modern  French  wnters,  lymphatic  ganglions,  are  small  solid  bodies 
placed  in  the  course  of  the  lymphatics  and  lacteals,  through  which  the 
contents  of  these  vessels  have  to  pass  in  their  progress  towards  the 
thoracic  or  the  right  lymphatic  duct.  These  bodies  are  collected  in 
numbers  along  the  course  of  the  great  vessels  of  the  neck,  also  in  the 
thorax  and  abdomen,  especially  in  the  mesentery  and  alongside  the 
aorta,  vena  cava  inferior  and  iliac  vessels.  A few,  usually  of  small 
size,  are  found  on  the  external  parts  of  the  head,  and  considerable 
groups  are  situated  in  the  axilla  and  groin.  Some  three  or  four  lie 
on  the  popliteal  vessels,  and  usually  one  is  placed  a little  below  the 
knee,  but  none  farther  down.  In  the  arm  they  are  found  as  low  as 
the  elbow-joint. 

A lymphatic  vessel  may  pass  through  two,  three,  or  even  more 
lymphatic  glands  in  its  course,  whilst,  on  the  other  hand,  there  are 
lymphatics  which  reach  the  thoracic  duct  without  encountering  any 
gland  in  their  way. 

The  size  of  these  bodies  is  very  various,  some  being  not  much  bigger 
than  a hempseed,  and  others  as  large  or  larger  than  an  almond  or  a 
kidney-bean.  In  shape  too  they  present  differences,  but  most  of  them 
are  round  or  oval. 

A lymphatic  gland  essentially  consists  of  a network  of  finely  divi- 
ded lymphatic  vessels,  on  and  between  which 
capillary  blood-vessels  are  ramified,  the  whole 
being  gathered  up  and  compacted  into  a compara- 
tively dense  mass  by  cellular  tissue,  which  at  the 
surface  of  the  gland  forms  for  it  an  inclosing  cap- 
sule. The  lymphatics  or  lacteals  which  enter  a 
gland  are  named  inferent  or  afferent  vessels  {vasa 
inferentia  seu  afferentia)  (fig.  265,  a,  b)  and  those 
which  issue  from  it,  efferent  vessels  {vasa  efferen- 
tia,)  {d,  e).  The  afferent  vessels,  on  approaching  a 
gland,  divide  into  many  small  branches  {b),  which 
enter  the  gland  and  by  their  further  ramifications, 
which  are  more  or  less  involved  or  tortuous,  form 
within  it  an  intricate  plexus  (c) ; from  this  plexus 
the  efferent  vessels  proceed  in  form  of  small 
branches  {d),  which  issue  from  the  gland,  and  at  a 
little  distance  beyond  it  unite  in  one  or  more 
trunks  (e),  usually  larger  in  size  but  fewer  in  num-  a lymphatic  gland  in- 
ber  than  those  of  the  afferent  vessels.  The  affe- 

, ^ , If-  • dried, — after  Hewson. — 

rent  and  etierent  vessels  are  thereiore  continuous  a b inferent,  d e efferent 
with  each  other  within  the  gland,  and  the  cellular  "vessels,  communicating 
cavities  described  by  some  anatomists  as  interve-  tics  within  the  gland; 
ning  between  them  and  serving  as  the  medium  of 
their  communication,  appear  to  be  nothing  more  than  partial  dilata- 
tions of  some  branches  of  the  common  connecting  plexus. 

The  plexiform  branches  of  lymphatics  within  the  glands  must  evidently  be 
collectively  more  capacious  than  the  afferent  or  efferent  vessels  with  which  they 

4* 


42 


LYMPHATIC  GLANDS. 


are  continuous,  and  hence  the  lynaph  or  chyle  must  move  more  slowly  through 
them,  and  while  thus  detained  or  delayed  in  the  gland,  it  is  brought  into  close 
relation  with  the  blood  of  the  numerous  capillaries  distributed  on  the  lymphatic 
plexus,  and  is  thus  placed  in  the  most  favourable  condition  for  receiving  matters 
from  that  fluid,  or  for  yielding  up  something  to  the  sanguiferous  system.  The 
transmission  of  matters  from  tlie  blood-vessels  to  the  lymphatics  within  the 
glands,  or  the  mutual  interchange  of  part  of  their  contents,  if  such  there  be,  would 
seem  therefore  to  take  place  not  by  means  of  inosculation  of  the  vessels,  but  by 
transudation  through  their  permeable  coats,  as  in  the  case  of  the  air  and  blood  in 
the  lungs. 

In  a gland  a large  number  of  plexiform  lymphatic  vessels,  presenting  a great 
extent  of  surface  for  the  contact  of  lymph  and  for  the  distribution  of  sanguiferous 
capillaries,  are  collected  into  a compact  mass  of  small  compass;  but  in  fishes 
and  reptiles,  in  which  there  are  no  lymphatic  glands,  and  in  birds,  in  which  there 
are  very  few,  the  purpose  served  by  them  is  accomplished  by  means  of  lymphatic 
netw'orks  occurring  in  various  parts  of  the  body,  especially  along  the  course  of  the 
larger  arteries.*  In  this  lax  or  expanded  form  of  lymphatic  gland,  as  it  might  be 
considered,  capillary  blood-vessels  are  distributed  on  the  lymphatic  plexus,  but 
the  different  elements  are  not  compacted  into  a solid  mass. 

It  is  known  that  the  lymph  and  chyle  contain  a greater  proportion  of  fibrin, 
and  are  consequently  more  perfectly  coagulable,  after  passing  the  glands,  and  it 
is  also  observed  that  the  proper  corpuscles  of  the  chyle  and  lymph  are  most 
abundant  nr  that  which  is  obtaiired  by  puncturing  the  small  brariches  of  lacteals 
or  lymphatics  on  the  glands.  From  this  latter  circumstance,  it  has  been  sup- 
posed that  these  corpuscles,  though  probably  also  generated  elsewhere  in  the 
lymphatic  and  lacteal  vessels,  are  principally  produced  in  the  glands,  and  this 
view  is  also  in  harmony  with  the  observations  of  Mr.  Goodsir  respecting  the 
modifications  of  structure  which  the  absorbent  vessels  present  within  these  organs. 
According  to  that  anatomist,  the  lymphatics  within  the  gland  lay  aside  all  but 
their  internal  coat  and  epithelium,  and  the  latter,  in  place  of  forming  a thin  lining 
of  flat  transparent  scales,  as  in  the  extra-glandular  lymphatics,  acquires  an  opaque 
granular  aspect,  and  is  converted  into  a thick  irregular  layer  of  spherical  nucle- 
ated corpuscles,  measuring  on  an  average  ^nVo^h  of  an  inch  in  diameter,  and 
suggesting  the  idea  of  lymph  or  chyle  corpuscles  generated  on  the  internal  mem- 
brane after  the  usual  manner  of  epithelium  cells,  and  about  to  be  thrown  off  into 
the  cavity  of  the  vessel.  Mr.  Goodsir  adds,  that  this  layer  is  thickest  in  those 
lymphatics  which  are  situated  towards  the  centre  of  the  gland,  and  becomes 
gradually  thinner  towards  the  afferent  and  efferent  vessels,  when  it  passes  con- 
tinuously into  the  ordinary  epithelium. 

Termination. — The  absorbent  system  discharges  its  contents  into  the 
veins  at  two  points,  namely,  at  the  junction  of  the  subclavian  and  in- 
ternal jugular  veins  of  the  left  side  by  the  thoracic  duct,  and  in  the  corre- 
sponding part  of  the  veins  of  the  right  side  by  the  right  lymphatic  trunk. 
The  openings,  as  already  remarked,  are  guarded  by  valves.  It 
sometimes  happens  that  the  thoracic  duct  divides,  near  its  termination, 
into  two  or  three  short  branches,  which  open  separately,  but  near  each 
other;  more  rarely,  a branch  opens  into  the  vena  azygos,  indeed  the 
main  vessel  has  been  seen  terminating  in  that  vein.  Again,  it  is  not 

* Not  only  do  the  lymphatics  of  many  oviparous  vertebrata  surround  the  larg'er  arteries 
in  form  of  close  plexuses,  but,  according  to  Rusconi,  the  aorta  and  mesenteric  arteries  of 
the  frog  and  salamander  are  actually  inclosed  in  wide  lymphatic  vessels.  It  has  been  pre- 
sumed that  in  instances  such  as  the  last  mentioned,  the  artery  is  separated  from  the  lymph 
by  a reflection  of  the  coat  of  the  containing  lymphatic  vessel,  but  Rusconi  maintains  that 
such  is  not  invariably  the  case.  See  his  work  entitled  Riflessioni  sopra  il  Systema  Linfa- 
tico  dei  Rettili,  Pavia,  1845,  in  which  will  also  be  found,  besides  many  interesting  observa- 
tions on  the  lymphatic  system  of  reptiles,  an  account  of  his  approved  method  of  injecting 
these  vessels. 


LYMPHATIC  HEARTS. 


43 


uncommon  for  larger  branches  which  usually  join  the  thoracic  duct, 
to  open  independently  in  the  vicinity  of  the  main  termination  ; and  this 
is  more  apt  to  happen  with  the  branches  which  usually  unite  to  form 
the  right  lymphatic  trunk.  By  such  variations  the  terminations  in  the 
great  veins  are  multiplied,  but  still  they  are  confined  in  man  to  the 
region  of  the  neck ; in  birds,  reptiles,  and  fish,  on  the  other  hand,  com- 
munications take  place  between  the  lymphatics  of  the  pelvis,  pos- 
terior extremities  and  tail,  with  the  sciatic  or  other  considerable  veins 
of  the  abdomen  or  pelvis. 

The  alleged  terminations  of  lymphatics  in  various  veins  of  the  abdomen,  de- 
scribed by  Lippi  as  occurring  in  man  and  mammalia,  have  not  been  met  with  by 
those  who  have  since  been  most  engaged  in  the  prosecution  of  this  department 
of  anatomical  research,  and  accordingly,  his  observations  have  generally  been 
either  rejected  as  erroneous,  or  held  to  refer  to  deviations  from  the  normal  con- 
dition.* But,  while  such  (extra-glandular)  terminations  in  other  veins  than  those 
of  the  neck  have  not  been  generally  admitted,  several  anatomists  of  much  autho- 
rity have  maintained  that  the  lacteals  and  lymphatics  open  naturally  into  veins 
within  the  lymphatic  glands.  This  latter  opinion,  which  has  been  strenuously 
advocated  by  Fohmann  in  particular,  is  based  on  a fact  well  known  to  every  one 
conversant  with  the  injection  of  the  vessels  in  question,  namely,  that  the  quick- 
silver usually  employed  for  that  purpose,  when  it  has  entered  a gland  by  the  in- 
ferent  lymphatics,  is  apt  to  pass  into  branches  of  veins  within  the  gland  and  thus 
find  its  way  into  the  large  venous  trunks  in  the  neighbourhood,  in  place  of  issuing 
by  the  efferent  lymphatic  vessels.  But,  although  it,  of  course,  cannot  be  doubted 
that,  in  such  cases,  the  mercury  gets  from  the  lymphatics  into  the  veins,  no  one 
has  yet  been  able  to  perceive  the  precise  mode  in  which  the  transmission  takes 
place,  and,  looking  to  the  circumstances  in  which  it  chiefly  occurs,  it  seems  to  be 
more  probably  owing  to  rupture  of  contiguous  lymphatics  and  veins  within  the 
glands,  than  to  a natural  communication  between  the  two  classes  of  vessels  m 
that  situation. 

Lymphatic  hearts. — Some  years  ago,  Muller  and  Panizza,  nearly  about  the  same 
time,  but  independently  of  each  other,  discovered  that  the  lymphatic  system  of 
reptiles  is  furnished,  at  its  principal  terminations  in  the  venous  system,  with 
pulsatile  muscular  sacs,  which  serve  to  discharge  the  lymph  into  the  veins. 
These  organs,  which  are  named  lymph-hearts,  have  now  been  found  in  all  the  dif- 
ferent orders  of  reptiles.  In  frogs  and  toads  two  pairs  have  been  discovered,  a 
posterior  pair,  situated  in  the  sciatic  region,  which  pour  their  lymph  into  a branch 
of  the  sciatic  or  of  some  other  neighbouring  vein,  and  an  anterior  more  deeply 
seated  pair,  placed  over  the  transverse  process  of  the  third  vertebra,  and  opening 
into  a branch  of  the  jugular  vein.  The  parietes  of  these  sacs  are  thin  and  trans- 
parent, but  contain  muscular  fibres  of  the  striated  kind,  disposed  spirally,  and 
decussating  in  different  layers,  as  in  the  blood-heart.  In  their  pulsations  they  are 
quite  independent  of  the  latter  organ,  and  are  not  even  synchronous  with  each 
other.  In  salamanders,  lizards,  serpents,  tortoises,  and  turtles,  only  a posterior 
pair  have  been  discovered,  which,  however,  agree,  in  all  essential  points,  with 
those  of  the  frog.f  In  the  goose,  and  in  other  species  of  birds  belonging  to  dif- 

* In  a recent  communication  inserted  in  Muller’s  Archiv.  for  1848,  p.  173,  Dr.  Nuhn, 
of  Heidelberg-,  maintains  the  regular  existence  of  these  abdominal  terminations,  and  refers 
to  three  instances  which  he  met  with  himself  In  two  of  these,  the  lymphatics  opened  into 
the  renal  veins,  and  in  the  other  into  tlie  vena  cava. 

t Rusconi,  who  has  lately  given  a description  and  figure  of  the  posterior  lymph-hearts 
of  the  frog  (Op.  cit.  p.  65;  Tav.  iv.  fig.  7),  suggests  (and  the  suggestion  is  not  peculiar  to 
him)  that  the  remarkable  pulsating  sac  connected  with  the  caudal  vein  of  the  eel,  which 
was  discovered  by  Dr.  Marshall  Hall,  and  the  sinuses  opening  into  other  veins,  in  certain 
fishes,  since  pointed  out  by  Hyrtl,  are  probably  of  the  same  nature  as  the -lymph-hearts  of 
reptiles. 


44 


ABSORBENTS. 


ferent  orders,  Panizza  discovered  a pair  of  lymph-sacs  opening  into  the  sacral 
veins,*  and  Stannius  has  since  found  that  these  sacs  have  striated  muscular  fibres 
in  their  parietes ; but,  although  this  observer,  in  some  cases,  exposed  them  in  the 
living  bird,  he  was  not  able  to  discover  any  pulsation  or  spontaneous  movement 
in  them.f 

Development  of  lymphatic  vessels. — Kolliker  states  that  he  has  observed  the  forma- 
tion of  lymphatics  from  ramified  cells  in  the  tails  of  young  salamander-larvee.  He 
states  that  the  process  takes  place  nearly  in  the  same  manner  as  in  the  case  of 
tlie  sanguiferous  capillaries  already  described ; the  only  notable  difference  being 
tliat,  whilst  the  growing  lymphatics  join  the  ramified  cells,  and  thus  extend  them- 
selves, their  branches  very  rarely  anastomose  or  become  connected  by  commu- 
nicating arches.  New-formed  lymphatics  have  been  injected  in  adhesions  be- 
tween inflamed  serous  membranes. 


THE  ABSORBENTS. 

The  absorbent  vessels  consist  of  the  lacteals,  which,  after  digestion, 
convey  the  chyle  from  the  alimentary  canal  to  the  thoracic  duct,  and 
of  the  lymphatics,  which  take  up  the  lymph  from  all  the  other  parts  of 
the  body,  and  return  it  through  the  thoracic  duct,  or  directly,  into  the 
venous  system.  Both  these  vessels  are  connected  in  their  course  with 
lacteal  or  lymphatic  glands. 

The  general  anatomy  of  the  absorbents  having  been  detailed,  their 
course  and  position  have  now  to  be  described. 

The  lacteals  all  terminate  in  the  thoracic  duct,  a large  common 
trunk,  which  also  receives  the  lymphatics  from  both  the  lower  limbs, 
from  the  cavity  of  the  abdomen  and  its  viscera,  (except  the  right  lobe 
of  the  liver,)  from  the  walls  of  the  abdomen,  and  from  the  left  side  of 
the  thorax,  from  the  left  lung,  the  left  side  of  the  heart,  and  left  side  of 
the  diaphragm,  from  the  left  upper  limb,  and  from  the  corresponding 
side  of  the  head  and  neck.  But  the  lymphatic  vessels  which  arise 
from  the  right  upper  limb,  the  right  side  of  the  head  and  neck,  from 
the  right  lung,  and  from  the  corresponding  half  of  the  liver  and  dia- 
phragm, terminate  by  a short  trunk,  which  enters  the  place  of  junction 
of  the  right  subclavian  and  internal  jugular  veins.  This  vessel  may 
be  called  \he  right  lymphatic  duct;  it  is  commonly  named  the  right 
thoracic  duct,  though  no  part  of  it  lies  within  the  thorax.  Indeed,  the 
duct  of  the  left  side  is  not  exclusively  thoracic;  for  its  commencement 
is  in  the  abdomen,  and  its  termination  in  the  neck.  The  thoracic 
duct,  the  right  lymphatic  duct,  and  all  the  principal  absorbent  vessels, 
are  provided  with  numerous  valves,  owing  to  the  constrictions  oppo- 
site which,  these  vessels  have  a varicose  appearance. 

* Osservazioni  antropo-zootomico-fisiologiche.  Pavia,  1830,  pp.  65  and  67. 
t Mailer’s  Archiv.,  1843,  p.  449. 


THE  LACTEALS. 


45 


The  lacteals  (vasa  lactea,  chylifera). — These  vessels  commence  in 
the  coals  of  the  intestines,  by  a very  close  plexus,  and  extend  to  the 
thoracic  duct,  in  which  they  all  terminate : they  are  derived  in  far 
larger  numbers  from  the  small  than  from  the  large  intestine,  so  that 
they  abound  in  the  mesentery,  and  particularly  in  that  part  of  it  which 
corresponds  with  the  jejunum  and  duodenum.  Two  sets  of  these  ab- 
sorbing vessels  are  found  along  the  tube  of  the  intestine,  having  differ- 
ent positions  and  directions.  Some  of  them,  for  example  those  nearer 
to  the  outer  surface  of  the  intestine,  run  longitudinally  in  the  course 
of  the  canal,  lying  beneath  its  peritoneal  coat ; whilst  others,  placed 
more  deeply  between  the  muscular  and  mucous  coats,  course  trans- 
versely around  the  intestine,  and  are  directed  thence  with  the  arteries 
and  veins,  along  the  mesentery,  enclosed  wdthin  the  folds  of  the  peri- 
toneum. It  was  at  one  time  supposed  that  the  more  superficial  ab- 
sorbents. of  the  intestine  were  lymphatics,  and  that  the  others  only 
were  lacteals;  but  such  a distinction  cannot  be  made  between  them, 
and  they  freely  communicate  and  anastomose  together.  “ The  lac- 
teals (says  Cruikshanlv)  absorb  chyle  when  it  is  presented  to  them ; 
and  at  other  times  they  absorb  other  fluids.”*  The  lacteals,  having 
entered  the  mesentery,  take  the  course  of  the  blood-vessels,  and  pass 
through  the  numerous  lymphatic  glands  (mesenteric  glands)  w'hich 
exist  within  these  peritoneal  folds.  The  mesenteric  glands  vary  in 
number  from  a hundred  and  thirty  to  a hundred  and  fifty;  and  in  the 
healthy  state  are  seldom  larger  than  an  almond.  They  are  most 
numerous  in  that  part  of  the  mesentery  which  corresponds  with  the 
jejunum ; and  they  seldom  occur  nearer  to  the  attached  border  of  the 
intestine  than  two  inches.  They  are  the  seat  of  unhealthy  deposits  in 
mesenteric  disease.  Small  glands  are  also  disseminated  irregularly 
between  the  folds  of  the  peritoneum  connected  with  the  large  intestine, 
but  they  are  not  numerous  in  that  situation. 

Having  passed  through  these  glands,  the  lacteals  gradually  unite  as 
they  approach  the  attached  border  of  the  mesentery,  two  or  three  per- 
haps joining  into  one;  and  so  they  become  diminished  in  number,  until 
at  length,  near  the  root  of  the  superior  mesenteric  artery,  only  two  or 
three  trunks  remain,  which  end  in  the  thoracic  duct.  Sometimes, 
however,  six  or  seven  of  these  vessels  open  separately  into  the  com- 
mencement of  the  duct.  In  this  way,  the  lacteals  from  the  whole  of 
the  small  intestine,  from  the  ceecum,  and  from  the  ascending  and  trans- 
verse parts  of  the  colon,  terminate ; those  from  the  descending  colon 
and  its  sigmoid  flexure  usually  join  some  of  the  lumbar  lymphatics,  or 
turn  upwards  and  open  by  a separate  trunk  into  the  lower  end  of  the 
thoracic  duct. 

To  the  same  point,  viz.,  the  lower  end  of  the  thoracic  duct,  may  be 
traced,  from  below  upwards,  the  lymphatic  vessels  from  the  lower 
limbs;  so  .that  the  thoracic  duct  may  be  said  to  commence  at  the 
common  point  of  junction  of  these  lymphatics  with  the  trunks  of  the 
lacteal  vessels. 


Anatomy  of  the  Absorbing  Vessels,  p.  161. 


46 


THORACIC  DUCT. 


THORACIC  DUCT. 

The  thoracic  duct  [ductus  thoracicus],  fig.  266,  h,  is  from  eighteen 
to  twenty  inclies  long  in  the  adult,  and  ex- 
tends usually  from  the  second  lumbar  verte- 
bra to  the  root  of  the  neck.  Its  commence- 
ment, however,  is  often  as  low  as  the  third 
lumbar  vertebra;  and  in  some  cases  as  high 
as  the  first  lumbar,  or  even  upon  the  last 
dorsal  vertebra.  Here  there  is  usually  a 
dilatation  of  the  duct,  of  variable  size,  which 
is  called  chyli  receptaculum  (Pecquet),  fig. 
266,  a.  The  thoracic  duct,  at  first,  lies  to 
the  left  side  of  and  behind  the  aorta,  and  is 
about  three  lines  in  diameter ; but  as  it 
ascends  it  passes  to  the  right  side  of  that 
vessel,  getting  into  contact  with  the  right 
crus  of  the  diaphragm,  and  so  reaches  the 
thorax,  where  it  is  placed  at  first  upon  the 
front  of  the  dorsal  vertebrae,  between  the 
aorta,  1,  and  the  azygos  vein,  8,  the  latter 
being  to  its  right  side.  It  ascends,  gradually 
inclining  to  the  left  and  at  the  same  time 
diminishing  in  size,  until  it  reaches  the  third 
dorsal  vertebra,  where,  after  passing  behind 
the  arch  of  the  aorta,  it  comes  into  contact 
with  the  oesophagus,  lying  between  its  left 
side  and  the  pleura.  Continuing  its  course, 
it  ascends  into  the  neck,  supported  by  the 
longus  colli  muscle,  until  it  arrives  on  a level 
with  the  upper  border  of  the  seventh  cervical 
vertebra,  where  it  changes  its  direction  and 
turns  forwards,  at  the  same  time  arching 
downwards  and  inwards  so  as  to  describe  a 
curve,  d,  and  then  terminates  on  the  outer 
side  of  the  internal  jugular  vein,  7,  in  the 
angle  formed  by  the  union  of  that  vein  with 
the  subclavian,  6.  The  diminution  in  the 
size  of  the  duct  as  it  ascends  has  been  al- 
I’eady  noticed ; at  the  fifth  dorsal  vertebra  it 
is  often  only  two  lines  in  diameter,  but  above 
this  point  it  enlarges  again.  It  is  generally 
waving  and  tortuous  in  its  course,  and  is 
constricted  at  intervals  or  varicose  in  its  ap- 
pearance. The  thoracic  duct  is  not  always 


The  aorta  is  marked  l.lhe  left 
subclavian  artery,  2,  the  left  ca- 
rotid 3,  the  upper  cava  4,  the  left 
innominate  vein  5,  the  left  sub- 
clavian vein  6,  the  left  internal 
jugular  vein  7,  the  azygos  vein 
8,  the  psoas  muscles  9,  9.  a,  b, 
b,  is  I he  thoracic  duct ; a,  the  re- 
ceptacnliim  chyli;  b,  the  trunk 
of  the  vessel ; d,  its  termination 
in  the  neck,  c is  the  right  lym- 
phatic duct.  J\,B.  The  rccepta- 
culum  chyli,  which  in  this  place 
is  placed  on  the  right  side  of  the 
aorta,  is  most  commonly  to  its 
lef  t side,  and  behind  it. 


a single  trunk  throughout  its  whole  extent : it 
frequently  divides  opposite  the  seventh  or 
eighth  dorsal  vertebra  into  two  trunks,  which 
soon  join  again : sometimes  in  its  course  it 


LYMPHATICS  OF  THE  LOWER  LIMB. 


47 


separates  into  three  divisions,  which  afterwards  unite,  and  enclose 
between  them  spaces  or  islets.  Cruikshank  in  one  case  found  the 
duct  double  in  its  entire  length  ; “ in  another  triple,  or  nearly  so.”  In 
the  neck,  the  thoracic  duct  often  divides  into  two  or  three  branches, 
which  in  some  instances  terminate  separately  in  the  great  veins,  but 
in  other  cases  unite  first  into  a common  trunk. 

The  thoracic  duct  has  numerous  double  valves  at  intervals  through- 
out its  whole  course,  which  are  placed  opposite  to  the  constricted 
parts  of  the  vessel.  They  are  more  numerous  in  the  upper  part  of  the 
duct.  At  the  termination  of  the  duct  in  the  veins  there  are  two 
valves,  so  placed  as  to  allow  the  contents  of  the  duct  freely  to  pass 
into  the  veins,  but  which  would  effectually  prevent  the  regurgitation 
of  either  chyle  or  blood  back  into  the  duct. 

THE  RIGHT  LYMPHATIC  DUCT. 

The  right  lymphatic  duct  [ductus  thoracicus  dexter  s.  minor],  fig. 
266,  c,  is  a short  vessel,  about  a line  or  line  and  a half  in  diameter, 
and  about  three  quarters  of  an  inch  in  length,  which  receives  the 
lymph  from  the  absorbents  of  the  right  upper  limb,  and  right  side  of 
the  head  and  chest.  It  enters  obliquely  into  the  receding  angle  formed 
by  the  union  of  the  right  subclavian  and  internal  jugular  veins,  where 
its  orifice  is  guarded  by  two  valves. 

The  course  of  those  lymphatic  vessels  which  pour  their  contents 
into  the  thoracic  duct  will  be  now  described,  beginning  with  those  of 
the  lower  limbs. 


LYMPHATICS  OF  THE  LOWER  LIMB. 

The  lymphatics  of  the  lower  limb  are  arranged  in  a superficial  and 
a deep  series. 

The  superficial  lymphatics,  [figs.  267,  268,]  placed  between  the  inte- 
gument and  fascia  of  the  limb,  are  arranged  into  two  sets,  of  which  one 
accompanies  the  long  saphenous,  whilst  the  other  follows  the  course  of 
the  short  saphenous  vein.  The  vessels  composing  the  first  or  internal 
set  commence  on  the  dorsum  and  inner  side  of  the  foot,  and,  passing 
partly  in  front  and  in  part  behind  the  inner  ankle,  ascend  along  the 
inner  side  of  the  knee  and  front  of  the  thigh,  and  terminate  in  the 
superficial  inguinal  glands.  In  their  course  these  vessels  are  joined 
by  numerous  branches  proceeding  from  the  integuments  of  the  leg  and 
the  thigh.  The  lymphatics  which  constitute  the  second  or  external 
division  of  the  subcutaneous  series,  are  much  less  numerous  than  those 
just  described.  Commencing  upon  the  outer  margin  of  the  foot,  they 
pass  behind  the  outer  malleolus,  and  ascend  along  the  back  part  of 
the  leg  ; here  they  perforate  the  fascia,  and  proceed  between  the  heads 
of  the  gastrocnemius  muscle  to  terminate  in  the  lymphatic  glands  of 
the  popliteal  space.  This  course  corresponds  with  that  of  the  short 
saphenous  vein,  which  these  lymphatics  accompany. 


4S 


DEEP-SEATED  LYMPHATICS. 


Fig.  267.  A view  of  tlie  superficial  lymphatics  of  the  thigh.  1.  The  external  or  saphena  minor 
vein.  2.  The  venous  anastomosis  below  the  patella.  3 Femoral  portion  of  the  saphena  major. 
4.  Point  where  it  enters  the  femoral  vein.  5.  The  great  chain  of  superficial  lymphatics  on  the 
inner  side  of  the  thigh.  6,  6.  A chain  of  three  or  four  parallel  trunks,  which  accompany  the 
saphena-major  vein.  7.  Branches  from  the  front  of  the  thigh.  8.  Branches  from  the  posterior 
part.  9,  9.  The  inguinal  glands  into  which  the  superficial  lymphatics  of  the  lower  extremity 
enter. 

Fig.  268.  The  superficial  lymphatics  of  the  inner  side  of  the  foot  and  leg.  1.  The  venous  anas- 
tomosis on  the  phalangeal  ends  of  the  metatarsal  bones.  2,  The  saphena  magna  vein.  3 Lym- 
phatics on  the  back  of  the  leg.  4.  The  same  vessels  on  the  lower  part  of  the  thigh.  5,  5.  Lym- 
phatics coming  from  the  sole  of  the  foot.  6,  6.  Lymphatics  from  the  dorsal  surface  of  the  foot. 
7.  The  lymphatics  which  accompany  the  saphena  veiu.  8.  Branches  of  lymphatics  from  the 
front  and  outside  of  the  leg.  9.  Branches  from  the  posterior  and  internal  side  of  the  calf  of  the 
leg.— S.  & H.] 


The  deep-seated  lymphatics  [figs.  269,  270]  of  the  lower  limb,  asso- 
ciated in  their  whole  course  with  the  deep  blood-vessels,  require  but  a 
brief  description.  In  the  leg,  they  consist  of  three  divisions,  namely,  an- 
terior tibial,  posterior  tibial,  and  peroneal.  Neither  these  nor  the  super- 
ficial absorbents  pass  through  any  lymphatic  gland  in  the  leg,  unless  it 
be  those  lymphatics  which  accompany  the  anterior  tibial  artery,  for  a 
small  gland  is  sometimes  found  on  the  front  of  the  interosseous  liga- 
ment, above  the  middle  of  the  leg.  The  several  sets  of  deep  lym- 


DEEP-SEATED  LYMPHATICS. 


49 


[Fig.  269.  Fig.  270. 


Fig.  269.  A front  view  of  the  deep-seated  lymphatics  of  the  thigh.  1.  Lower  end  of  the 
aorta.  2.  Primitive  iliac  vein.  3,  4.  E,vternal  iliac  artery  and  vein.  5.  Femoral  artery.  6. 
Section  of  the  femoral  vein.  7.  Vena  saphena  on  the  leg.  8.  Lymphatics  near  the  knee.  9. 
Lymphatics  accompanying  the  femoral  vessels.  10.  Deep  lymphatics  going  from  the  inside  of 
the  thigh  to  the  glands  in  the  groin.  11.  Lymphatics  of  the  external  circumflex  vessels.  12. 
Lymphatics  on  the  outer  side  of  the  femoral  vessels.  13.  A lymphatic  gland  always  found  out- 
side of  the  vessels.  14.  A collection  of  vessels  and  glands  from  the  internal  iliac  vessels.  15. 
The  lymphatics  of  the  primitive  iliac  vessels. 

Fig.  270.  The  deep-seated  lymphatic  vessels  and  glands  on  the  back  of  the  leg.  1.  Popliteal 
artery.  2.  Popliteal  vein.  3.  Posterior  tibial  vessels ; the  artery  is  between  its  two  veins.  4. 
Peroneal  artery  and  veins.  5.  Lymphatic  vessels  from  the  front  of  the  leg,  coming  through  the 
opening  in  the  interosseous  ligament.  6.  Deep-seated  lymphatic  vessels  which  arise  in  the  sole 
of  the  foot  and  accompany  the  blood-vessels.  7.  Anastomosis  of  the  superficial  and  deep-seated 
lymphatics.  8,  9.  Uniting  branches  of  posterior  tibial  lymphatics.  10,  10.  Popliteal  glands 
which  receive  the  deep  lymphatics  of  the  leg  and  foot.  11, 11.  Efferent  popliteal  trunks  which 
accompany  the  blood-vessels  to  the  femoral  glands. — S.  & H.] 

phatics  in  the  leg  ascend  with  the  blood-vessels,  and  enter  the  lym- 
phatic glands  situated  in  the  popliteal  space.  These  (the  'popliteal 
lymphatic  glands)  are  usually  very  small,  and  four  or  five  in  number; 
they  surround  the  popliteal  vessels,  and  are  embedded  in  a quantity  of 
loose  fat.  The  popliteal  glands  receive  from  below,  the  deep  lym- 
phatics of  the  leg  and  those  which  accompany  the  short  saphenous 
vein  ; and  from  them  proceed  efferent  vessels,  which  ascend  with  the 
femoral  artery  to  the  groin. 

VOL.  II. 


5 


50 


LYMPHATICS  OF  THE  ABDOMEN  AND  PELVIS. 


The  lymphatic  glands  of  the  groin,  inguinal  glands,  like  the  lym- 
phatic vessels  of  that  part,  are,  from  their  relative  position,  divisible 
into  a superficial  and  a deep  set ; the  former  being  placed  immediately 
under  the  integument,  the  latter  under  the  fascia  lata.  The  superficial 

glands  [fig.  271,]  are  larger 


[Fig-.  271. 


The  lymphjitic  vessels  and  glands  of  the  groin  of  the 


than  the  others ; their  num- 
ber varies  much,  but  may 
be  stated  to  average  about 
eight  or  ten  ; they  are  dis- 
posed ii’regularly  about  Pou- 
part’s  ligament  and  the  saphe- 
nous opening  of  the  fascia  ; a 
few  sometimes  extend  for  two 
or  three  inches  downwards 
on  the  saphenous  vein.  The 
deep-seated  glands  [fig.  269,] 
are  placed  behind  the  others, 
around  the  femoral  artery 
and  vein. 

Besides  the  lymphatics  of 
the  low'er  limb,  the  inguinal 
glands  are  joined  by  the 
superficial  absorbent  vessels 
from  the  perinaeum  and  the 


right  side.  1.  Saphena  magna  vein.  2.  Veins  on  the  external  generative  Organs, 
^i.face  of  the  abdomen.  3.  External  pndic  vein.  4.  gg  ^,j]|  Pg  presently  noticed, 
1 he  lymphatic  vessels  collecied  in  fasciculi  and  accom-  , , i * r *^1  i 

panying  the  saphena  vein  on  its  inner  side.  5.  The  ex-  3110  by  ttlOS6  irom  lIlG  lower 
ternal  irnnhsoflhe  same  set  of  vessels.  6.  The  lympha-  part  of  the  abdominal  Walls, 
tic  gland  which  receives  all  these  vessels.  It  is  placed  t . 

on  the  termination  of  the  saphena  vein.  7.  The  effe-  and  the  integUmenIS  Covering 
rent  trunks  from  this  gland;  they  become  deep-seated  {Pg  outer  side  of  the  pelvis. 
and  accompany  the  femoral  artery.  8.  One  of  the  more  rni  i i i • J 

external  lymphatic  glands  of  the  groin.  9.  A chain  of  1 he  deep  lymphatics,  derived 
four  or  live  inguinal  glands,  which  receive  the  lympha-  from  the  muscles  On  the  pel- 
tics  from  the  genitals,  abdomen,  and  external  portion  of  . , , . 

the  thigh.-s.  & II.]  VIS,  and  many  proceeding 

from  the  adductor  muscles  of 
the  thigh,  in  company  with  the  gluteal,  sciatic,  and  obturator  arteries, 
enter  the  cavity  of  the  pelvis  with  those  vessels,  and  pass  through  a 
series  of  glands  situated  in  the  neighbourhood  of  the  internal  and 
common  iliac  arteries.  The  efferent  vessels  of  the  superficial  inguinal 
glands  perforate  the  fascia,  come  into  connexion  with  those  situated 
deeply,  pass  into  the  abdomen  by  the  side  of  the  blood-vessels,  and 
terminate  in  a chain  of  lymphatics  lying  along  the  external  iliac 
artery,  and  ending  in  the  lumbar  glands. 

LYMPHATICS  OF  THE  ABDOMEN  AND  PELVIS. 

Superficial  lymphatics  of  the  abdomen  and  pelvis  [fig.  271].  The 
lymphatic  vessels  of  the  icalls  of  the  abdomen  and  pelvis  consist  of 
several  series,  which  pursue  different  directions,  but  are  all  associated 
with  the  blood-vessels  of  different  parts.  A superficial  series,  derived 
from  the  integument  of  the  lower  part  of  the  abdomen  (from  the  umbi- 
licus downwards),  descends  towards  the  superficial  inguinal  glands; 
whilst  a deep-seated  .series  in  the  same  situation  is  also  directed  down- 


LYMPHATICS  OF  THE  ABDOMEN  AND  PELVIS. 


51 


wards,  and  ends  in  the  glands  situated  on  the  external  iliac  artery : 
these  two  sets  follow  respectively  the  superficial  and  deep  epigastric 
blood-vessels.  Other  lymphatics,  proceeding  from  the  side  and  back 
part  of  the  walls  of  the  abdomen,  perforate  the  fibres  of  the  muscles ; 
a small  number  of  them  then  wind  round  the  crest  of  the  ilium,  passing 
in  their  course  through  one  or  two  small  glands,  and  proceed  along 
Poupart’s  ligament  with  the  circumflex  iliac  artery,  to  terminate  in  the 
glands  upon  the  external  iliac  artery  ; whilst  the  greater  number  are 
directed  backwards  with  the  ilio-lumbar  and  lumbar  arteries,  and, 
being  joined  by  the  lymphatics  from  the  muscles  and  integument  of 
the  back,  pass  behind  the  psoas  muscle  to  the  vertebral  column,  where 
they  enter  the  glands  surrounding  the  aorta  and  lower  vena  cava. 

The  swperficial  lymphatics  of  the  pelvis,  as  already  described,  are 
directed  for  the  most  part  towards  the  inguinal  glands. 

The  superf.cial  lymphatics  of  the  penis  usually  form  three  vessels, 
two  being  placed  at  the  sides,  and  the  other  on  the  dorsum  of  the 
organ.  Commencing  in  the  prepuce,  they  pass  backwards,  unite  on 
the  dorsum  penis,  and,  again  subdividing,  send  branches  on  each  side 
to  the  inguinal  glands. 

The  lymphatics  of  the  scrotum,  with  those  from  the  integuments  of 
the  perineum,  may  be  associated  together ; for  all,  guided,  as  it  wmre, 
by  the  superficial  pudic  vessels,  enter  the  inguinal  lymphatic  glands. 
The  deep-seated  lymphatics  of  the  penis  accompany  the  internal  pudic 
vessels,  and  end  in  the  glands  on  the  internal  iliac  artery. — The  lym- 
phatics of  the  external  generative  organs  in  the  female  present  a similar 
disposition  to  that  here  described  in  the  male. 

Deep  lymphatics  of  the  pelvis  and  abdomen — lymphatics  of  the  vis- 
cera.— The  course  of  these  deep  lymphatic  vessels,  as  in  other  parts, 
is  indicated  by  that  of  the  principal  blood-vessels. 

The  lymphatics  of  the  bladder,  taking  rise  from  the  entire  surface  of 
that  organ,  enter  the  glands  placed  about  the  internal  iliac  artery : 
with  these  are  associated  the  lymphatics  of  the  prostate  gland  and  of 
the  vesiculas  seminales. 

The  lymphatics  of  the  rectum  are  frequently  of  considerable  size : 
immediately  after  leaving  the  intestine,  some  of  them  pass  through 
small  glands  which  lie  contiguous  to  it;  finally,  they  enter  the  lym- 
phatic glands  situated  in  the  hollow  of  the  sacrum,  or  those  higher  up 
in  the  loins. 

In  the  unimpregnated  state  of  the  uterus,  its  lymphatics  are  small, 
but  during  the  period  of  gestation  they  are  considerably  enlarged. 
Issuing  from  the  entire  substance  of  the  organ,  the  greater  number  de- 
scend, together  with  those  of  the  vagina,  and  pass  backwards  to  enter 
the  glands  upon  the  internal  iliac  artery ; thus  pursuing  the  course  of 
the  principal  uterine  blood-vessels.  Others,  proceeding  from  the  upper 
end  of  the  uterus,  run  outwards  in  the  folds  of  peritoneum  which  con- 
stitute its  broad  ligaments,  and  join  the  lymphatics  derived  from  the 
ovaries  and  Fallopian  tubes.  The  conjoined  vessels  then  ascend  with 
the  ovarian  arteries,  near  the  origin  of  which  they  terminate  in  the 
lymphatic  vessels  and  glands  placed  on  the  aorta  and  vena  cava. 

The  lymphatics  of  the  testicle  commence  in  the  substance  of  the 
gland,  and  upon  the  surface  of  the  tunica  vaginalis.  Collected  into 


52 


LYMPPIATICS  OF  THE  ABDOMEN  AND  PELVIS. 


several  large  trunks,  they  ascend  with  the  other  constituents  of  the 
spermatic  cord,  pass  through  the  inguinal  canal,  and  accompany  the 
spermatic  vessels  in  the  abdomen  to  enter  the  lumbar  lymphatic  glands. 

The  lymphatics  of  the  kidney. — Those  placed  upon  the  surface  of  the 
organ  are  comparatively  small ; they  unite  at  the  hilus  of  the  kidney 
Avith  other  lymphatics  from  the  substance  of  the  gland,  and  then  pass 
inwards  to  the  lumbar  lymphatic  glands.  The  lymphatics  of  the 
supra-renal  capsules  unite  with  those  of  the  kidney.  The  lymphatic 
vessels  of  the  ureter  are  numerous ; they  communicate  with  those  of 
the  kidney  and  the  bladder,  and  for  the  most  part  terminate  with  the 
former. 

The  lymphatics  of  the  stomach  are  placed,  some  beneath  the  peri- 
toneal coat,  and  others  between  the  muscular  and  mucous  coats. 
Following  the  direction  of  the  blood-vessels,  they  become  arranged 
into  three  sets.  One  set  accompanies  the  coronary  vessels,  and  re- 
ceiving, as  it  runs  from  left  to  right,  branches  from  both  surfaces  of 
the  organ,  turns  backwards  near  the  pylorus,  to  join  some  of  the 
larger  trunks.  Another  series  of  lymphatics,  from  the  left  end  of  the 
stomach,  follow  the  vasa  brevia,  and  unite  with  the  lymphatics  of  the 
spleen ; whilst  the  third  set,  guided  by  the  right  gastro-epiploic  vessels, 
incline  from  left  to  right  along  the  great  curvature  of  the  stomach, 
from  which  they  pass  backwards,  and  at  the  root  of  the  mesentery 
terminate  in  one  of  the  pi'incipal  lacteal  vessels. 

The  lymphatics  of  the  spleen  are  placed,  some  immediately  under 
its  peritoneal  covering,  others  in  the  substance  of  the  organ.  Both  sets 
converge  to  the  inner  side  of  the  spleen,  come  into  contact  with  the 
blood-vessels,  and,  accompanying  these,  pass  through  a series  of  small 
glands,  and  terminate  in  the  lymphatics  of  the  digestive  organs. 

Lymphatics  emerge  from  the  pancreas  at  different  points,  and  join 
those  derived  from  the  spleen. 

The  lymphatics  of  the  liver  are  divisible  into  three  principal  sets, 
accordingly  as  they  are  placed  upon  its  upper  or  its  under  surface,  or 
are  spread  through  its  substance  with  the  blood-vessels. 

The  lymphatic  vessels  scattered  upon  the  upper  surface  of  the  liver 
incline  towards  particular  points,  and  so  become  distinguishable  into 
groups,  of  which  four  are  ordinarily  enumerated.  Thus,  from  the 
middle  of  this  surface  of  the  liver,  five  or  six  branches  run  towards  the 
falciform  ligament,  on  which,  directed  forwards,  they  unite  to  form  a 
large  trunk,  which  passes  upwards  between  the  fibres  of  the  dia- 
phragm, behind  the  ensiform  cartilage.  Having  reached  the  inter- 
pleural space,  behind  the  sternum,  they  ascend  through  a chain  of  lym- 
phatic glands,  found  upon  the  internal  mammary  blood-vessels,  and 
are  thus  conducted  to  the  root  of  the  neck,  generally  at  the  right  side, 
where  they  terminate  in  the  right  lymphatic  duct.  The  second  group 
consists  of  vessels  which  incline  outwards  towards  the  right  lateral 
ligament,  opposite  to  which  they  unite  into  one  or  two  larger  lym- 
phatics, which  pierce  the  diaphragm  and  run  forward  upon  its  upper 
surface  to  join  the  preceding  set  of  vessels  behind  the  sternum.  In 
some  cases,  however,  instead  of  passing  into  the  thorax,  they  turn  in- 
wards on  reaching  the  back  part  of  the  liver,  and,  running  upon  the 


LYMPHATICS  OF  THE  ABDOMEN  AND  PELVIS. 


53 


crus  of  the  diaphragm,  open  into  the  thoracic  duct  close  to  its  com- 
mencement. A similar  set  of  lymphatics  is  found  upon  the  left  lobe 
of  the  liver;  the  vessels  of  which  it  is  composed,  after  reaching  the 
left  lateral  ligament,  pierce  the  diaphragm,  and,  turning  forwards,  end 
in  the  glands  in  the  anterior  mediastinum.  Finally,  along  the  fore  part 
of  the  liver,  some  vessels  will  be  observed  to  turn  downwards  and  join 
those  placed  upon  its  under  surface. 

The  under  surface  of  the  liver  is  covered  by  an  open  network  of 
lymphatic  vessels.  On  the  right  lobe,  they  are  directed  over  and 
under  the  gall-bladder  to  the  transverse  fissure,  where  some  join  the 
deep  lymphatics  ; whilst  others,  after  passing  through  some  scattered 
lymphatic  glands,  are  guided  by  the  hepatic  artery  to  the  right  side  of 
the  aorta,  where  they  termi- 
nate in  the  thoracic  duct. 

Branches  also  proceed  to  the 
concave  border  of  the  sto- 
mach, between  the  folds  of 
the  small  omentum,  to  join 
with  the  coronary  lympha- 
tics of  that  organ. 

The  deep  lymphatics  of  the 
liver  accompany  the  branches 
of  the  portal  vein  in  the  sub- 
stance of  the  organ,  and  pass 
out  of  the  gland  by  the  trans- 
verse fissure.  After  commu- 
nicating with  the  superficial 
lymphatics,  and  also  with 
those  of  the  stomach,  they 
pass  backwards,  and,  at  the 
side  of  the  coeliac  artery,  join 
with  one  of  the  lacteal  trunks 
previously  to  its  termination 
in  the  thoracic  duct. 

The  - absorbent  vessels  of 
the  intestines,  named  the  lac- 
teals,  have  been  already  de- 
SCribeO  (ante,  page  44).  So,  A front  view  of  the  femoral  iliac  and  aortic  lym- 
too,  have  the  mesenteric  l.  Saphena  magna  vem. 

, , 1 • I 1 iliac  artery  and  vein.  3.  Pnmnive  iliac 

glands  connected  wilh  those  anery  and  vein.  4.  The  aoria.  5.  Ascending  vena 
vessels  (p.  45).  It  now  re-  6,  7.  Lymphatics  which  are  alongside  of  the 

saphena  vein  on  the  ihigh.  8.  Lower  set  of  inguinal 
mams  to  consider  the  other  lymphatic  glands  which  receive  these  vessels.  9.  Su- 

lymphatic  glands  situated  in  '"gy'“^  bn'ph“tic  glands  whu-h  receiv 

\ ^ ^ . 1 « . , these  vessels.  10,  The  chain  of  lymphatics  in 


the  pelvic 
cavities. 


and 


, ■ • , . jv..  . ....  ....ui.i  I, 111  front 

abdominal  of  the  external  iliac  vessels.  11.  Lymphatics  which 
accompany  the  circumflex  iliac  vessels.  12.  Lumbar 
rp,  7 , 7 7 aortic  lymphatics.  l.T  Afferent  trunks  of  the 

X ne  Lymphatic  glands  OJ  the  lumbar  glands,  lorming  the  origin  of  the  thoracic 
pelvis  and  abdomen  [fig.  272.]  Thoracic  duct  at  its  commencement.— 

— The  lymphatics  of  the  lower 

half  of  the  body  may  be  followed,  within  the  abdomen,  to  a conti- 
nuous series  of  glands  situated  in  front  of  the  sacrum  and  vertebral 

5* 


54 


LYMPHATICS  OF  THE  THORAX. 


column.  Though  connected  by  absorbent  vessels  passing  from  one  to 
the  other,  these  glands  are  more  numerous  at  particular  points,  and 
are  accordingly  arranged  into  several  groups.  In  the  pelvis,  some  of 
the  glands  are  placed  behind  the  rectum  in  the  hollow  of  the  sacrum, 
and  are  hence  named  sacral  lymphatic  glands.  Others,  again,  sur- 
rounding the  internal  iliac  artery  are  denominated  the  internal  iliac 
glands.  They  receive  the  lymphatics  corresponding  to  the  branches 
of  the  internal  iliac  artery,  and  comtnunicate  upwards  with  the  lumbar 
glands. 

The  lumbar  lymphatic  glands  are  very  large  and  numerous ; they 
are  placed  in  front  of  the  lumbar  vertebrae,  around  the  aorta  and  vena 
cava.  To  these  may  be  traced  the  lymphatics  of  the  lower  limb,  as 
well  as  those  which  accompany  several  of  the  branches  of  the  abdo- 
minal aorta. 

The  efferent  absorbent  vessels  which  proceed  from  these  glands 
progressively  increase  in  size,  u'hile  their  number  diminishes,  and  at 
length  they  unite  into  a few  trunks,  which,  with  those  of  the  lacteals, 
form  the  origin  of  the  thoracic  duct. 

THE  LYMPHATICS  OF  THE  THOEAX. 

The  lymphatics  of  the  thorax  are  divisible  into  two  sets,  viz.,  those 
derived  from  the  walls,  and  those  from  the  viscera  of  that  cavity. 
The  former  are  arranged  in  tw'o  distinct  planes,  one  lying  between 
the  skin  of  the  muscles,  the  other  being  deeply  seated.  The  superfi- 
cial lymphatics  at  the  front  of  the  chest  run  upon  the  great  pectoral 
muscle,  and  for  the,  most  part  are  directed  towards  the  axilla,  where 
they  enter  the  lymphatic  glands.  Those  upon  the  back  lie  on  the 
trapezius  and  latissimus  dorsij  and,  inclining  from  various  directions, 
also  converge  to  the  axilla,  and  end  in  the  same  series  of  glands  as 
the  lymphatics  of  the  upper  limb.  The  deep  absorbents  at  the  fore 
part  of  the  chest  correspond,  in  their  general  distribution,  with  the 
internal  mammary  artery  ; commencing  in  the  muscles  of  the  abdo- 
men, they  ascend  between  the  fibres  of  the  diaphragm  at  its  attach- 
ment to  the  ensiform  cartilage,  and  then  continue  behind  the  costal 
cartilages  to  the  top  of  the  thorax.  In  their  course  they  receive 
branches  from  the  anterior  part  of  the  intercostal  spaces,  and  ulti- 
mately terminate  on  the  left  side  in  the  thoracic  duct,  and  on  the 
opposite  side  in  the  right  lymphatic  duct. 

The  deep  lymphatics  at  the  sides  and  back  part  of  the  chest  follow 
the  distribution  of  the  aortic  intercostal  arteries : they  receive  absorb- 
ent vessels  which  come  forwards,  through  the  intertransverse  spaces, 
from  the  parts  seated  in  the  vertebral  grooves,  and  other  vessels  from 
each  side  which  run  along  the  intercostal  spaces.  All  these  incline 
inwards  to  the  spine,  and  terminate  in  the  thoracic  duct. 

The  lymphatics  of  the  lungs,  like  those  of  other  organs,  form  two 
sets,  one  being  superficial,  the  other  deep-seated.  Those  at  the  surface 
run  beneath  the  pleura,  where  they  form  a network  by  their  anasto- 
moses. Their  number  is  considerable,  but  they  are  sometimes  diffi- 
cult of  demonstration.  “ I have  been  able,”*  says  Cruikshank,  “ at 
one  time  to  show  the  whole  external  surface  of  the  lungs  covered 
* Anatomy  of  tlie  Absorbents,  p.  194. 


LYMPHATICS  OF  THE  THORAX. 


55 


with  absorbents  I had  injected  ; at  another  time  I have  not  been  able 
to  find  one.” 

One  of  the  easiest  methods  of  finding  them  is  to  inflate  the  lungs  of  a still-hom 
child  from  the  trachea;  the  air  passes  from  the  cells  into  the  absorbents,  and 
enables  us  to  see  those  on  the  surface  : if  a puncture  be  made  into  one  of  them 
with  a lancet,  the  air  will  partially  escape,  and  then  the  injecting  pipe,  contain- 
ing a column  of  quicksilver,  can  be  introduced.* 

Most  of  these  superficial  lymphatics  converge  to  the  root  of  the 
lungs,  and  terminate  in  the  bronchial  glands. 

The  deep  lymphatics  of  the  lungs  run  with  the  blood-vessels  along 
the  bronchi : they  communicate  freely  with  those  upon  the  surface, 
and  at  the  root  of  the  lungs  open  into  the  bronchial  glands.  From 
these,  two  or  three  trunks  issue,  which  ascend  along  the  trachea  to 
the  root  of  the  neck,  and  terminate  on  the  left  side  in  the  thoracic 
duct,  and  on  the  right  in  the  lymphatic  duct  of  that  side. 

The  lymphatics  of  the  heart  follow  the  coronary  vessels  from  the 
apex  of  the  organ  towards  its  base.  Those  of  the  right  side  meet 
near  the  origin  of  the  aorta,  so  as  to  form  a trunk  of  some  size,  which 
runs  upwards  over  the  aortic  arch,  and  passes  backwards  between 
the  innominate  and  left  carotid  arteries,  to  reach  the  trachea,  along 
which  it  ascends  to  the  root  of  the  neck,  to  terminate  in  the  right 
lymphatic  duct.  The  left  lymphatics  of  the  heart  ascend  to  the  base 
of  the  organ ; where  they  communicate  with  the  preceding  set,  and 
having  united  into  a single  vessel,  proceed  along  the  pulmonary 
artery,  towards  its  bifurcation.  At  this  point  the  vessel  passes  through 
some  lymphatic  glands  behind  the  arch  of  the  aorta,  and  ascends  by 
the  trachea  to  terminate  in  the  thoracic  duct. 

The  lymphatics  of  the  oesophagus  form  along  that  tube  a plexus  of 
vessels,  passing  upwards  upon  it,  and  traversing  the  glands  which  lie 
in  their  course : after  having  communicated  by  anastomoses  with  the 
lymphatics  of  the  lungs,  at  and  near  the  roots  of  those  organs,  they 
terminate  in  the  thoracic  duct. 

The  lymphatics  of  the  thymus  gland  and  those  of  the  thyroid  body 
may  be  described  with  the  absorbents  of  the  thorax. 

“ On  the  spinal  surface  of  the  thymus  gland,”  Sir  Astley  Cooper 
observes,!  “ numerous  absorbent  glands  are  found ; and  if  these  be 
injected,  many  absorbents  are  discovered.  But  upon  the  posterior 
surface  of  the  cornua  and  cervical  portion,  two  large  vessels  proceed 
on  each  cornu,  and  the  side  of  the  trachea. — They  pass  nearly  straight 
upon  the  spinal  surface  of  the  cornua,  converging  a little  as  they  pro- 
ceed towards  the  sternum,  and  terminate  in  the  jugular  veins  by  one 
or  more  orifices  on  each  side.” 

The  lymphatics  of  the  thyroid  gland. — From  each  lateral  lobe  of  this 
organ  some  absorbing  vessels  arise,  which  converge  and  unite  to  form 
one  short  trunk,  that  opens  at  the  right  side  into  the  right  lymphatic 
duct,  at  the  left  into  the  thoracic  duct.  They  may  be  demonstrated 
by  inserting  the  injecting  pipe  into  the  substance  of  the  gland,  when 
the  mercury,  by  its  weight,  will  force  its  way  into  the  lymphatics. 

The  lymphatic  glands  of  the  thorax. — In  describing  the  vessels, 
mention  has  already  been  made  of  the  glands  through  which  they 
* Loc.  cit.  t Ana-tomy  of  the  Thymus  Gland,  p.  14. 


66 


LYMPHATICS  OF  THE  UPPER  LIMB. 


pass  in  various  situations.  Thus,  along  the  course  of  the  internal 
mammary  blood-vessels  there  are  placed  six  or  seven  small  glands, 
through  which  the  lymphatics  behind  the  sternum  pass ; they  may  be 
named  the  anterior  mediastinal  glands.  Three  or  four  lymphatic 
glands  (cardiac)  lie  behind  the  aortic  arch,  and  one  before  it ; and 
another  cluster,  varying  from  fifteen  to  twenty  in  number,  are  found 
along  the  oesophagus  {oesophageal  glands).  At  the  root  of  the  lungs 
there  are  ten  or  twelve  glands  of  much  larger  size  than  those  just 
mentioned.  These  are  the  bronchial  glands.  The  largest  of  them 
occupy  the  interval  between  the  right  and  left  bronchi  at  their  bifur- 
cation, whilst  others  of  smaller  size  rest  upon  these  tubes  for  a short 
distance  within  the  lungs.  In  early  infancy  their  colour  is  pale  red  ; 
tow'ards  puberty,  w'e  find  them  verging  to  gray,  and  studded  with  dark 
spots ; at  a more  advanced  age  they  are  frequently  very  dark.  In 
chronic  diseases  of  the  lungs  they  sometimes  become  enlarged  and 
indurated,  so^s  to  press  on  the  air-tubes,  and  cause  much  irritation. 
They  are  frequently  the  seat  of  tuberculous  deposits. 

LYMPHATICS  OF  THE  UPPER  LIMB. 

In  the  upper  limb,  as  in  the  lower,  the  lymphatics  are  arranged  into 
a superficial  and  a deep  set — the  former  accompanying  the  subcuta- 
neous veins,  the  latter  following  the  course  of  the  deep  blood-vessels. 

The  superficial  lymphatics  [fig.  273.]  form  two  divisions,  which  cor- 
respond with  the  subcutaneous  veins  on  the  outer  and  inner  borders 
of  the  forearm.  One  set  accompanies  the  branches  of  the  ulnar  cuta- 
neous vein  from  the  inner  border  of  the  hand,  along  the  front  and 
inner  side  of  the  fore-arm  as  high  as  the  bend  of  the  elbow.  In  this 
course  they  receive  numerous  collateral  branches,  and  join  at  the 
point  just  indicated  with  some  of  those  I’rom  the  outer  side  of  the 
fore-arm.  Continuing  their  course  upwards  along  the  arm,  a few 
of  them  passing  through  a lymphatic  gland  situated  in  front  of 
the  inner  condyle  of  the  humerus,  these  absorbent  vessels  termi- 
nate either  in  glands  placed  along  the  brachial  artery,  or  in  those 
of  the  axilla,  where  they  unite  with  the  deep  lymphatics.  Those 


[Fig.  273. 


The  superficial  lymphatic  vessels  of  the  upper  extremity. — 1.  The  median  vein.  2.  Cephalic 
vein.  3.  Posterior  basilic  vein.  4.  Median  cephalic.  5.  Cephalic  vein  high  up  the  arm.  6. 
Median  basilic  vein.  7.  Superficial  lymphatics  of  the  hand.  8.  Lymphatic  trunks  from  the 
inside  of  the  hand.  9,  9.  Principal  fasciculus  of  lymphatics  from  the  front  and  back  of  the  fore- 
arm. 10.  A branch  from  the  superficial  to  the  deep  lymphatics  of  the  fore-arm.  11.  An  acci- 
dental lymphatic  gland.  12.  Superficial  lym[)hatics  which  dip  down  with  the  basilic  vein.  13. 
The  lymphatic  glands  of  the  axilla,  which  receive  the  lymphatic  vessels  of  the  arm. — S.  cfc  H.] 


LYMPHATICS  OF  THE  HEAD  AND  NECK. 


57 


which  constitute  the  second  set,  placed  along  the  outer  border  of  the 
fore-arm,  are  less  numerous  than  the  preceding.  They  commence 
beneath  the  integuments  on  the  outer  and  back  part  of  the  hand,  and 
follow  the  course  of  the  radial  cutaneous  veins  to  the  bend  of  the 
elbow  ; here  the  greater  number  of  them  join  the  vessels  last  de- 
scribed, whilst  a few  ascend  with  the  cephalic  vein,  on  the  outer  side 
of  the  arm,  and  passing  with  that  vessel  between  the  deltoid  and  great 
pectoral  muscles,  end  beneath  the  clavicle  in  one  or  more  lymphatic 
glands,  connected  with  those  at  the  lower  part  of  the  neck. 

The  deep  lymphatics  of  the  upper  limb  correspond  with  the  deep 
blood-vessels.  In  the  fore-arm  they  consist,  therefore,  of  three  sets, 
associated  with  the  radial,  ulnar,  and  interosseous  arteries  and  veins ; 
in  their  progress  upwards,  they  have  frequent  communications  with 
the  superficial  lymphatics.  Some  of  them  enter  the  glands  which  lie 
near  the  brachial  artery;  and  all  terminate  in  the  glands  of  the  axilla. 

The  axillary  glands  are  generally  ten  or  twelve  in  number ; in  this 
respect,  however,  as  well  as  in  their  size,  they  vary  considerably  in 
different  individuals  ; they  are  placed  along  the  axillary  vessels,  em- 
bedded in  a quantity  of  loose  cellular  tissue,  and  a few  are  situated  at 
some  distance  below  the  vessels,  against  the  serratus  magnus  muscle. 
They  receive  all  the  lymphatics  of  the  arm  already  described,  as  well 
as  those  proceeding  from  the  integuments  of  the  back,  from  the  fore 
part  of  the  thorax,  and  from  the  mammary  gland.  Hence  they  are 
liable  to  be  influenced  by  diseases  affecting  any  of  those  parts. 

From  the  glands  in  the  axilla,  efferent  lymphatic  vessels,  fewer  in 
number,  but  larger  in  size  than  the  afferent  vessels,  proceed  along  the 
course  of  the  subclavian  artery,  in  some  parts  twining  round  it.  From 
the  top  of  the  thorax  they  ascend  into  the  neck,  close  to  the  subcla- 
vian vein,  and  terminate,  those  of  the  left  side  in  fhe  thoracic  duct, 
those  of  the  right  side  in  the  right  lymphatic  duct.  Sometimes  they 
unite  into  a single  trunk,  which  opens  separately  into  the  subclavian 
vein  near  its  termination. 

LYMPHATICS  OF  THE  HEAD  AND  NECK. 

The  lymphatics  of  the  head  include  those  of  the  cranium  and  the 
face. 

Commencing  beneath  the  scalp,  the  lymphatics  of  the  cranium  join 
together  so  as  to  diminish  in  number  whilst  they  increase  in  size,  and 
are  at  length  collected  into  an  anterior  and  a posterior  set,  which 
follow  respectively  the  course  of  the  temporal  and  the  occipital  arte- 
ries. The  temporal  set  descend  in  front  of  the  ear,  some  of  the  vessels 
passing  through  one  or  two  glands  usually  found  near  the  zygoma, 
whilst  others  enter  those  situated  on  the  parotid  gland ; all  of  them  ter- 
minate in  the  lymphatic  glands  of  the  neck.  The  occipital  set  of  the 
cranial  lymphatics,  accompanying  the  occipital  artery,  descends  to  the 
glands  situated  behind  the  ear  (over  the  mastoid  process  of  the  tem- 
poral bone),  and  thence  joins  the  superficial  lymphatics  of  the  neck. 

Within  the  cranial  cavity,  lymphatic  vessels  have  been  demon- 
strated in  the  pia  mater  and  in  the  arachnoid  membrane.  None  have 
been  injected  in  the  dura  mater,  nor  have  they  been  shown  in  the  sub- 


58 


LYMPHATICS  OF  THE  HEAD  AND  NECK. 


Stance  of  the  brain.  The  trunks  of  those  derived  from  the  pia  mater 
pass  out  of  the  skull  with  the  veins. 

The  supei'ftcial  lymphatics  of  the  face,  more  numerous  than  those  of 
the  cranium,  descend  obliquely  in  the  course  of  the  facial  vein,  and 
join  the  glands  placed  beneath  the  base  of  the  lower  maxillary  bone; 
a few  of  them  in  their  descent  pass  through  one  or  two  glands  situated 
over  the  buccinator  muscle.  The  deep  lymphatics  of  the /ace  are  de- 
rived from  the  cavities  of  the  nose  and  mouth,  and  proceed  in  the 
course  of  the  internal  maxillary  artery : having  reached  the  angle  of 
the  jaw,  they  enter  the  glands  situated  in  that  place. 

The  lymphatic  glands  found  on  different  parts  of  the  head  and  face 
are  few  and  very  small : those  of  the  neck,  on  the  contrary,  are  com- 
paratively large  and  very  numerous. 

The  cervical  glands  are  almost  all  placed  on  the  sides  of  the  neck, 
and  are  divisible  into  a superficial  and  a deep  series.  Of  the  former, 
some  lie  beneath  the  base  of  the  inferior  maxillary  bone;  the  re- 
mainder, arranged  along  the  course  of  the  external  jugular  vein,  occur 
in  greatest  number  in  the  angular  space  behind  the  lower  end  of  the 
sterno-mastoid  muscle,  where  that  vein  enters  the  subclavian  vein  ; at 
this  point  the  cervical  glands  approach  and  are  connected  with  the 
glands  of  the  axilla.  The  deep  cervical  glands  are  placed  along  the 
carotid  artery  and  internal  jugular  vein,  extending  downwards  on  the 
sheath  of  those  vessels  as  far  as  the  thorax. 

The  lymphatic  vessels  of  the  cranium  and  face  (already  described), 
together  with  those  of  the  pharynx,  larynx,  and  other  parts  of  the 
neck,  pass  into  the  cervical  glands.  From  these  efferent  vessels  issue, 
which  progressively  diminish  in  number  during  their  descent,  and 
unite  into  a single  trunk  at  the  bottom  of  the  neck.  On  the  left  side 
this  single  vessel  usually  enters  the  thoracic  duct,  close  to  its  termina- 
tion, and  on  the  opposite  side  ends  in  the  right  lymphatic  duct : some- 
times, however,  it  terminates  sepai'ately  at  the  junction  of  the  subcla- 
vian and  internal  jugular  veins,  or  in  one  of  those  vessels,  immediately 
before  they  unite. 


EPIDERMIC,  EPITHELIAL  OR  CUTICULAR 

TISSUE. 


It  is  well  known,  that  Vv^hen  the  skin  is  blistered,  a thin  and  nearly 
transparent  membrane,  named  the  cuticle  or  epidermis,  is  raised  from 
its  surface.  In  like  manner,  a transparent  film  may  be  raised  from 
the  lining  membrane  of  the  mouth,  of  the  same  nature  as  the  epider- 
mis, although  it  has  in  this  situation  received  the  name  of  “ epithe- 
lium and  under  the  latter  appellation,  a coating  of  the  same  kind 
exists  on  nearly  all  free  surfaces  of  the  body.  It  is  true,  that  in  many 
situations  the  epithelium  cannot  be  actually  raised  from  the  subjacent 
surface  as  a coherent  membrane,  still  its  existence  as  a continuous 
coating  can  be  demonstrated  ; and,  although  in  different  parts  it  pre- 
sents other  important  differences,  it  has  in  all  cases  the  same  funda- 
mental structure,  and  its  several  varieties  are  connected  by  certain 
common  characters. 

The  existence  of  a cuticular  covering  in  one  form  or  other,  has  been 
demonstrated  in  the  following  situations  : viz.  1.  On  the  surface  of  the 
skin.  2.  On  mucous  membranes;  a class  of  membranes  to  be  after- 
wards described,  which  line  those  internal  cavities  and  passages  of  the 
body  that  open  exteriorly,  viz.  the  alimentary  canal,  the  lachrymal, 
nasal,  tympanic,  respiratory,  urinary  and  genital  passages  ; as  well  as 
the  various  glandular  recesses  and  ducts  of  glands,  which  open  into 
these  passages  or  upon  the  surface  of  the  skin.  3.  On  the  inner  or  free 
surface  of  serous  membranes,  which  line  the  walls  of  closed  cavities 
in  the  head,  chest,  abdomen,  and  other  parts.  4.  On  the  membranes 
termed  synovial  within  the  joints.  5.  On  the  inner  surface  of  the 
blood-vessels  and  lymphatics. 

This  tissue  has  neither  vessels  nor  nerves,  and  it  is  wholly  devoid  of 
sensibility  ; it,  nevertheless,  possesses  a decidedly  organized  structure. 
Wherever  it  may  exist,  it  is  formed  essentially  of  nucleated  cells  united 
together  by  a more  or  less  cohesive  intercellular  matter.  The  cells, 
in  whatever  way  they  may  be  produced,  make  their  appearance  first 
in  the  deepest  part  of  the  structure,  in  a soft  blastema  deposited  by  the 
blood-vessels  of  the  subjacent  tissue ; then,  usually  undergoing  consider- 
able changes  in  size,  figure,  and  consistency,  they  gradually  rise  to  the 
surface,  where,  in  most  cases,  and  perhaps  in  all,  they  are  thrown  off 
and  succeeded  by  others  from  beneath.  In  many  situations  the  cells 
form  several  layers,  in  which  they  may  be  seen  in  different  stages  of 
their  progress,  from  their  first  appearance  to  their  final  desquamation. 
The  layer  or  layers  thus  formed,  take  the  shape  of  surface  to  which 


60 


SCALY  EPITHELIUM. 


they  are  applied,  following  accurately  all  its  eminences,  depressions, 
or  other  inequalities. 

In  accordance  with  the  varied  purposes  which  the  epithelium  is  des- 
tined to  fulfil,  the  cells  of  which  it  is  composed  come  to  difler  in  differ- 
ent situations,  in  their  figure,  their  size,  their  position  in  respect  of 
each  other,  their  degree  of  mutual  cohesion,  and  in  the  nature  of  the 
matter  they  contain,  as  well  as  the  vital  endowments  which  they 
manifest;  and,  founded  on  these  modifications  of  its  constituent  cells, 
four  principal  varieties  of  epithelium  have  been  recognised,  namely, 
the  scaly,  the  columnar,  the  spheroidal,  and  the  ciliated,  each  of  which 
will  now  be  described  in  particular. 

It  may  first  be  remarked,  however,  that  amidst  these  changes  the 
nucleus  of  the  cell  undergoes  little  alteration,  and  its  characters  are 
accordingly  remarkably  uniform  throughout.  It  is  round  or  oval,  and 
more  or  less  flattened ; its  diameter  measures  from  to  of  an 
inch,  or  more.  Its  substance  is  insoluble  in  acetic  acid,  and  colour- 
less, or  has  a pale  reddish  tint.  It  usually  contains  one  or  two  nucle- 
oli, distinguished  by  their  strong,  dark  outline ; and  a variable  number 
of  more  faintly-marked  granules  irregularly  scattered.  For  the  most 
part,  the  ni^leus  is  persistent,  but  in  some  cases  it  disappears  from  the 
cell. 


Fig.  274. 


The  scaly,  lamellar,  tabular,  or  flattened  epithelium  (pavement,  or 
tessellated  epithelium  of  the  German  anatomists).  In  this  variety  the 
epithelium  particles  have  the  form  of  small  angular  tables,  or  thin 
scales;  in  some  situations,  forming  a single  thin  layer,  in  others  accu- 
mulating in  many  superimposed  strata,  so  as  to  afford  to  the  parts 
they  cover  a defensive  coating  of  considerable  strength  and  thickness. 

As  a simple  layer,  it  is  found  on  the  serous  membranes,  the  inner 
surface  of  the  heart,  the  blood-vessels,  and  absorbents. 

If  the  surface  of  the  peritoneum,  pleura,  pe- 
ricardium or  other  serous  membrane  be  gently 
scraped  with  theedge  of  a knife,a  small  quan- 
tity of  soft  matter  will  be  brought  away,  which, 
when  examined  with  the  microscope,  will  be 
found  to  contain  little  shred-like  fragments 
of  epithelium,  in  which  a greater  or  less 
number  of  its  constituent  particles  still  hold 
together,  like  the  pieces  composing  a mosaic 
work  (fig.  274.)  These  particles,  which  are 
flattened  cells,  have,  for  the  most  part,  a 
polygonal  figure,  and  are  united  to  each 
Each  has  a nucleus 
^peritoneum,)  Jq  qj-  near  the  centre.  The  addition  of  weak 
h,  n“ucieus ; c,  nucieoiL— (Henfe.)’  acetic  acid  renders  the  angular  outline  of  the 

cells  as  well  as  the  nucleus  more  distinct. 
The  cells  differ  somewhat  in  size  on  different  parts  of  the  serous  mem- 
brane. 

The  epithelium  of  the  vascular  system  resembles  in  many  parts  that 
of  the  serous  membranes ; but  in  some  situations  the  flattened  cells, 
together  with  their  nuclei,  assume  an  oblong  figure,  and  sometimes 
their  outline  becomes  indistinct  from  blending  of  neighbouring  cells. 


Fragment  of  epithelium  from  a Other  by  their  edges, 
erous  membrane 


SCALY  EPITHELIUM. 


61 


Fig.  275. 


A sealy  epithelium  in  which  the  cells  form  several  layers,  (thence 
named  “ stratified,”  by  Henle,)  covers  the  skin,  where  it  constitutes 
the  scarf-skin,  or  epidermis,  which,  together  with  the  hairs  and  nails, 
will  be  afterwards  more  fully  described.  In  this  form  it  exists,  also, 
on  the  conjunctival  covering  of  the  eyeball;  on  the  membrane  of  the 
nose  for  a short  distance  inwardly;  on  the  tongue  and  the  inside  of 
the  mouth,  throat,  and  gullet;  on  the  vulva  and  vagina,  extending 
some  way  into  the  cervix  of  the  uterus  ; also  (in  both  sexes)  on  a 
very  small  extent  of  the  membrane  of  the  urethra,  adjoining  the  ex- 
ternal orifice.  It  is  found,  also,  on  the  synovial  membranes  which 
line  the  joints.  Its  principal  use,  no  doubt,  is  to  afford  a protective 
covering  to  these  surfaces,  which  are  almost  all  more  or  less  exposed 
to  friction. 

The  cells  in  this  sort  of  epithelium  become  converted  into  broad 
thin  scales,  which  are  loosened  and 
cast  off  at  the  free  surface.  Such  scales, 
both  single  and  connected  in  little 
patches,  may  be  at  all  times  seen  with 
the  microscope,  in  mucus  scraped 
from  the  inside  of  the  mouth,  as  shown 
in  fig.  275  ; but  to  trace  the  progressive 
change  of  the  cells,  they  must  be  suc- 
cessively examined  at  different  depths 
from  the  surface,  and  the  epithelium 
must  also  be  viewed  in  profile,  or  in  a 
perpendicular  section,  as  exhibited  in 
figure  276.  In  this  manner,  at  the  deep  or  attached  surface,  small 
cells  may  be  seen  in  the  midst  of  a soft  granular,  or  clear  substance 
(blastema).  These  appear  to  be  recently  formed,  for  their  cell  mem- 
brane closely  invests  the  nucleus ; nay,  it  is  alleged  by  good  observers, 
that  mere  nuclei  are  also  present,  which  subsequently  acquire  an  en- 
velope. A little  higher  up  in  the  mass  the  cells  are  enlarged ; they 
have  a globular  figure,  and  are  filled  with  soft  matter;  they  next  be- 
come flattened,  but  still  retain  their  round  or  oval  outline  ; then  the 
continued  flattening  causes  their  opposite  sides  to  meet  and  cohere, 
except  where  separated  by  the  nucleus,  and  they  are  at  length  con- 
verted into  thin  scales,  which  form  the  uppermost  layers.  While 
they  are  undergoing  this  change  of  figure,  their  substance  becomes 
more  firm  and  solid,  and  their  chemical  nature  is  more  or  less  altered  ; 
for  the  cell-membrane  of  the  softer  and  more  deep-seated  cells  may 
be  dissolved  by  acetic  acid,  which  is  not  the  case  with  those  nearer 
the  surface.  The  nucleus  at  first  enlarges,  as  well  as  the  cell,  but  in 
a much  less  degree ; and  it  soon  becomes  stationary  in  its  growth, 
having  usually  acquired  an  oval  figure,  and  an  eccentric  position. 
The  scales  near  the  surface  overlap  a little  at  their  edges,  and  their 
figure  is  very  various ; somewhat  deeper  it  is  mostly  polygonal,  and 
more  uniform.  Besides  the  nuclei,  they  often  exhibit  small  scattered 
granules,  like  dots,  and,  according  to  Henle,  are  sometimes  marked 
over  with  fine  parallel  lines. 

In  various  parts,  the  more  superficial  and  denser  layers  of  the  scaly 

VOL.  II.  6 


Epithelium  scales  from  the  inside  of 
the  mouth,  magnified  260  diameters. 
(Henle.) 


62 


COLUMNAR  EPITHELIUM. 


epithelium  can  be  readily  separated  from  the  deeper,  more  recently 
formed,  and  softer  part  which  lies  underneath  ; and  this  has  led  to  the 


Fig.  276. 


Epithelium  from  the  conjunctiva  of  the  calf,  folded  so  that  the  free  surface  forms  the  upper 
border  of  the  figure,  and  rendered  transparent  by  acetic  acid.  1,  2,  3,  4,  5,  progressive  flattening 
of  the  cells  as  they  rise  to  the  surface.  The  outline  figures  represent  single  cells  from  different 
depths,  viewed  on  their  surface;  and  at  4'  and  5',  edgeways.  Magnified  410  diameters.  (Chiefly 
after  Henle.) 

error  of  describing  the  latter  as  a distinct  membrane,  under  the  name 
oi  rete  mucosum ; this  point  will  be  again  noticed  in  treating  of  the 
skin. 

Columnar  Epithelium. — In  this  variety,  (figs.  277  and  278,)  the 
constituent  cells  are  elongated  in  a direction  perpendicular  to  the  sur- 
face of  the  membrane,  so  as  to  form  short  upright  columns,  smaller 
or  even  pointed  at  their  lower  or  attached  extremity,  and  broader  at 
the  upper.  They  are  mostly  flattened  on  their  sides,  by  which  they 
are  in  mutual  apposition,  at  least  in  their  upper  and  broader  part,  and 
have,  therefore,  so  far  a prismatic  figure,  their  broad  flat  ends  appear- 
ing at  the  surface  of  the  epithelium,  in  form  of  little  polygonal  areas 
(fig.  277  c.)  The  nucleus,  usually  oval,  is  placed  near  the  middle  of 
the  column,  and  is  often  so  large,  in  proportion  to  the  cell,  as  to  cause 
a bulging  at  that  part;  in  which  case,  Mr.  Bowman*  observes,  the 
height  of  the  nucleus  differs  in  contiguous  columns,  the  better  to  allow 

Fig.  277. 


D 


A,  B,  columns  of  epithelium  from  the  intestine,  magnified,  c.  Viewed  by  their  broad  free 
extremity,  d.  Seen  in  a transverse  section  of  an  intestinal  villus.  (From  Henle.) 


COLUMNAR  EPITHELIUM. 


63 


Fig-.  278. 


of  mutual  adaptation.  The  particles  from  the  epithelium  of  the  gall- 
bladder, are  mostly  without  nuclei  (Henle).  Besides  the  nucleus,  the 
columnar  cell  usually  contains  a certain  amount  of  an  obscurely  gra- 
nular matter ; this  may  be  distributed  throughout  the  whole  of  the 
particle,  or  confined  to  its  middle  and  lower  end,  the  upper  part  of  the 
column  remaining  transparent ; or  lastly,  the  granular  matter  may  be 
surrounded  on  all  sides  by  a transparent  border,  which  some  have 
supposed  to  be  the  wall  of  the  cell. 

The  little  columns  are  held  together, 
though  sometimes  very  feebly,  by  intercellu- 
lar substance,  which  fills  up  the  wider  space 
between  their  narrow  ends,  and  even  extends 
beyond  their  large  extremities,  and  forms  a 
continuous  layer  over  them  on  the  free  sur- 
face of  the  epithelium. 

The  columnar  epithelium  is  unquestionably 
subject  to  shedding  and  renovation,  but  the 
precise  mode  in  which  this  take 
not  been  ascertained.  — (Henie.) 


Columnsofepithelium  from  the 
rabbit’s  intestine.  I.  Free  sur- 
face. 3.  Broad  outer  end.  3. 
Nucleus.  4.  Small 


inner  ex- 


place  has  uemity  turned  towards  the  rau- 
^ cous  membrane.  308  diameters. 


Valentin  infers,  from  h.is  observations,  that  in  most  parts  there  are  young  cells 
in  successive  stages  of  advancement,  lying  underneath  the  columnar  particles, 
and  preparing  to  take  their  place,  as  occurs  in  the  cuticle  and  other  correspond- 
ing forms  of  the  scaly  epithelium.  But  in  some  situations,  the  little  columns 
appear  to  rest  immediately  on  the  subjacent  membrane,  without  any  appearance 
of  an  hitervening  layer.  Perhaps  the  epithelial  coating  may  not  undergo  a slow 
and  continual  shedding  and  renewal,  but  may  from  time  to  time  be  cast  off  en- 
tirely and  at  once;f  in  which  case,  the  subjacent  surface  may  remain  denuded  for 
a short  time,  until  its  covering  is  restored,  or  a new  epithelium  may  be  formed 
preparatory  to  the  shedding  of  the  old,  and  ready  to  succeed  it.  Some  have  sup- 
posed,J that  a temporary  denudation  takes  place  in  certain  situations  and  circum- 
stances ; it  has  been  stated,  for  instance,  that  the  epithelium  is  thrown  off  from 
the  inner  surface  of  the  intestines,  during  digestion,  in  order  to  enable  the  subja- 
cent membrane  to  exercise  the  special  function,  and  that,  when  this  is  accom- 
plished, the  epithelial  covering  is  speedily  reproduced.  Others  § consider  the 
separation  of  the  epithelium  in  these  cases  as  accidental. 

The  columnar  variety  of  epithelium  is  confined  to  mucous  mem- 
branes. It  is  found  in  the  stomach  ; on  the  mucous  membrane  of  the 
intestines  in  its  whole  extent;  in  the  whole  length  of  the  urethra,  ex- 
cept a small  part  at  the  orifice.  It  extends  along  the  ducts  of  the 
greater  number  of  glands,  whether  large  or  small,  which  open  on  the 
mucous  membrane,  but  not  throu2;h  iheir  entire  length  ; for,  at  their 
extremities,  these  ducts  have  an  epilhelium  of  a different  character. 
The  inner  membrane  of  the  gall-bladder  is  covered  with  columnar 
epithelium. 

Spheroidal  epithelium. — In  this  variety,  the  cells  for  the  most  part 
retain  their  primitive  roundness,  or,  being  flattened  where  they  touch, 


* Cyclopedia  of  Anatomy,  art.  Mucous  Membrane. 

t [This  I have  observed  to  be  undoubtedly  the  case  in  insects  and  Crustacea. — J.  L.] 
t Goodsir,  Edin.  New  Phil.  Journal,  vol.  xxxiii.  Mr.  G.  thinks,  that  the  primarv  or 
basement  membrane  which  lies  immediately  underneath  the  epithelium,  contains  persis- 
tent  and  proligerous  nuclei,  which  serve  as  reproductive  centres  for  new  epithelium  cells. 

§ Reichert  and  Bidder.  Muller’s  Archiv.  1843  ; Jahresbericht,  p.  231.  Bidder  found, 
that  when  proper  care  was  taken,  the  gastric,  as  well  as  intestinal  epilhelium,  was  always 
entire. 


64 


CILIATED  EPITHELIUM. 


acquire  a polyhedral  figure,  in  which  no  one  dimension  remarkably 
predominates.  Hence,  llie  above  term  was  applied  to  this  form  of 
epithelium  by  Mr.  Bowman.*  But  in  some  places  the  cells  show  a 
tendency  to  lengthen  into  columns,  and  in  others  to  flatten  into  tables, 
especially  when  this  epithelium  approaches  the  confines  of  one  or  other 
of  the  preceding  varieties;  in  such  cases  Henle  names  it  transitional ; 
moreover,  when  the  scaly  and  columnar  varieties  border  with  one 
another,  the  figure  of  their  particles  is  gradually  changed,  presenting 
various  intermediate  forms;  in  other  words,  the  epithelium  there  puts 
on  the  transitional  character,  though  it  may  be  only  for  a very  small 
space. 

The  greatest  stretch  of  spheroidal  epithelium  is  found  in  the  urinary 
passages,  where  it  succeeds  the  columnar  epithelium  of  the  urethra  at 
the  internal  orifice  of  that  canal,  and  lines  the  whole  of  the  bladder, 
ureters,  and  pelves  of  the  kidneys.  It  is  found  also  in  the  excretory 


Fig.  279. 


ducts  of  the  mammary,  perspiratory,  and  of 
many  mucous  glands,  and  a modification  of 
the  spheroidal  epithelium  lines  the  inmost 
secreting  cavities,  or  commencing  ducts  of 
glands  generally  (fig.  279).  In  this  last- 
mentioned  situation,  the  nucleated  cells  con- 
tain a large  proportion  of  fine  granular  mat- 
ter; in  some  cases  even,  the  peculiar  ingre- 
dients of  the  secretion  may  be  recognised  in 
— (Dr'lla?™ liver,  magnified,  them;  and  it  is  Conceived,  that  they  have  a 

considerable  share  in  preparing  or  separating 
these  matters  from  the  blood. 

Ciliated  Epithelium. — In  this  form  of  epithelium,  the  particles,  which 
are  generally  columnar,  bear  at  their  free  extremities  little  hair-like 
processes,  which  are  agitated  incessantly  during  life,  and  for  some 
time  after  death,  with  a lashing  or  vibrating  motion.  These  minute 
and  delicate-moving  organs  are  named  cilia.  They  have  now  been 
discovered  to  exist  very  extensively  throughout  the  animal  kingdom; 
and  the  movements  they  produce  are  subservient  to  very  varied  pur- 
poses in  the  animal  economy. 

In  the  human  body  the  ciliated  epithelium  occurs  in  the  following 
parts,f  viz.: — 1.  On  the  mucous  membrane  of  the  air  passages  and  its 
prolongations.  It  commences  at  a little  distance  within  the  nostrils, 
covers  the  membrane  of  the  nose  and  of  the  adjoining  bony  sinuses, 
extends  up  into  the  nasal  duct  and  lachrymal  sac,  is  interrupted  then 
by  scaly  epithelium  which  lines  the  lachrymal  canals,  but  reappears  on 
the  conjunctiva  of  the  eyelids.  From  the  nose  it  spreads  backwards 
a certain  way  on  the  upper  surface  of  the  soft  palate,  and  into  the 
upper  or  nasal  region  of  the  pharynx;  also  into  the  eustachian  tube, 
and  tympanum.  The  remainder  of  the  pharynx  is  covered  by  scaly 
epithelium  as  already  mentioned;  but  the  ciliated  epithelium  begins 
again  in  the  larynx  a little  above  the  glottis,  and  continues  throughout 
the  trachea  and  the  bronchial  tubes  in  the  lungs  to  their  smallest  rami- 

* Cyclop,  of  Anat.,  art.  Mucous  Membrane, 
t Henle,  Allgemeine  Anatoinie,  p.  246. 


CILIATED  EPITHELIUM. 


65 


fications.  2.  On  the  mucous  lining  of  the  uterus  and  fallopian  tubes, 
and  even  on  the  peritoneal  surface  of  the  latter  at  their  fimbriated  ex- 
tremities. 3.  On  the  parietes  of  the  ventricles  of  the  brain. 

In  other  mammiferous  animals  as  far  as  examined,  cilia  have  been 
found  in  nearly  the  same  parts.  To  see  them  in  motion,  therefore,  a 
portion  of.  ciliated  mucous  membrane  may  be  taken  from  the  body  of 
a recently  killed  quadruped.  The  piece  of  membrane  is  to  be  folded 
with  its  free  or  ciliated  surface  outwards,  placed  on  a slip  of  glass,  with 
a little  water  or  serum  of  blood,  and  covered  with  a bit  of  thin  glass 
or  mica.  When  it  is  now  viewed  with  a magnifying  power  of  200 
diameters,  or  upwards,  a very  obvious  agitation  will  be  perceived  on 
the  edge  of  the  fold,  and  this  appearance  is  caused  by  the  moving  cilia 
with  which  the  surface  of  the  membrane  is  covered.  Being  set  close 
together,  and  moving  simultaneously  or  in  quick  succession,  the  cilia, 
when  in  brisk  action,  give  rise  to  the  appearance  of  a bright  trans- 
parent fringe  along  the  fold  of  the  membrane,  agitated  by  such  a rapid 
and  incessant  motion,  that  the  single  threads  which  compose  it  cannot 
be  perceived.  The  motion  here  meant,  is  that  of  the  cilia  themselves; 
but  they  also  set  in  motion  the  adjoining  fluid,  driving  it  along  the 
ciliated  surface,  as  is  indicated  by  the  agitation  of  any  little  particles 
that  may  accidentally  float  in  it.  The  fact  of  the  conveyance  of  fluids 
and  other  matters  along  the  ciliated  surface,  as  well  as  the  direction 
in  which  they  are  impelled,  may  also  be  made  manifest  by  immersing 
the  membrane  in  fluid,  and  dropping  on  it  some  finely  pulverized  sub- 
stance, (such  as  charcoal  in  fine  powder,)  which  will  be  slowly  but 
steadily  carried  along  in  a constant  and  determinate  direction ; and 
this  may  be  seen  with  the  naked  eye,  or  with  the  aid  of  a lens  of  low 
power. 

The  ciliary  motion  of  the  human  mucous  membrane  is  beautifully 
seen  on  the  surface  of  recently  extracted  nasal  polypi;  and  single 
ciliated  particles,  with  their  cilia  still  in  motion,  are  sometimes  sepa- 
rated accidentally  from  mucous  surfaces  in  the  living  body,  and  may 
be  discovered  in  the  discharged  mucus;  or  they  may  even  be  pur- 
posely detached  by  gentle  abrasion.  But  the  extent  and  limits  of  the 
ciliated  epithelium  of  the  human  body  have  been  determined  chiefly 
from  its  anatomical  characters. 

Cilia  have  now  been  shown  to  exist  in  almost  every  class  of  ani- 
mals, from  the  highest  to  the  lowest.  The  immediate  purpose  which 
they  serve  is,  to  impel  matters,  generally  more  or  less  fluid,  along  the 
surfaces  on  which  they  are  attached ; or,  to  propel  through  a liquid 
medium  the  ciliated  bodies  of  minute  animals,  or  other  small  objects 
on  the  surface  of  which  cilia  are  present;  as  is  the  case  with  many 
infusorial  animalcules,  in  which  the  cilia  serve  as  organs  of  locomo- 
tion, like  the  fins  of  larger  aquatic  animals,  and  as  happens,  too,  in 
the  ova  of  many  vertebrated  as  well  as  invertebrate  animals,  where 
the  yolk  revolves  in  its  surrounding  fluid  by  the  aid  of  cilia  on  its  sur- 
face. In  many  of  the  lower  tribes  of  aquatic  animals,  the  cilia  acquire 
a high  degree  of  importance;  producing  the  flow  of  water  over  the 
surface  of  their  organs  of  respiration,  indispensable  to  the  exercise  of 
that  function ; enabling  the  animals  to  seize  their  prey,  or  to  swallow 

6* 


66 


CILIATED  EPITHELIUM, 


their  food,  and  performing  various  other  offices  of  greater  or  less  im- 
portance in  iheir  economy.  In  man,  and  the  warm-hlooded  animals, 
their  use  is  apparently  to  impel  secreted  fluids,  or  other  matters,  along 
the  ciliated  surfaces,  as,  for  example,  tlie  mucus  of  the  wind-pipe  and 
nasal  sinuses,  which  they  carry  towards  the  outlet  of  these  cavities. 

The  cells  of  the  ciliated  epithelium  (figs.  280  and  281),  contain 
nuclei,  as  usual ; they  have  most  generally  an  elongated  or  prismatic 
form,  like  the  particles  of  the  columnar  epithelium,  which  they  resem- 
ble, too,  in  arrangement.  The  cilia  are  attached  to  their  broad  or 


Fig.  280.  Fig.  281. 


Columnar  ciliated  epithelium  cells  diameters, 

from  the  human  nasal  membrane.  Mag- 
nified 300  diameters. 

superficial  extremities,  each  columnar  particle  bearing  a tuft  of  these 
minute  hair-like  processes.  In  some  cases,  the  cells  are  spheroidal  in 
figure,  the  cilia  being  still,  of  course,  confined  to  that  portion  of  the 
cell  which  forms  part  of  the  general  surface  of  the  epithelial  layer 
(fig.  281).  Instances  of  the  latter  form  occur  in  the  epithelium  of  the 
frog’s  mouth,  on  the  surface  of  the  ovum,  and,  according  to  Valentin,* 
on  the  choroid  plexuses  of  foetal  quadrupeds. 

The  cilia  themselves  differ  widely  in  size  in  different  animals,  and 
they  are  not  equal  in  all  parts  of  the  same  animal.  In  the  human 
windpipe  they  are,  according  to  Valentin’s  measurement,  to 
of  an  inch  long;  but  in  many  invertebrate  animals,  especially  such  as 
live  in  salt  water,  they  are  a great  deal  larger.  In  figure  they  have 
the  aspefit  of  slender,  conical,  or  slightly  flattened  filaments;  broader 
at  the  base  and  usually  pointed  at  their  free  extremity.  Their  sub- 
stance is  transparent,  soft,  and  flexible.  It  is  to  all  appearance  homo- 
geneous, and  no  fibres,  granules,  or  other  indications  of  definite  internal 
structure,  have  been  satisfactorily  discovered  in  it. 

There  is  reason  to  believe,  that  the  ciliated  epithelium  of  the  uterus 
is  from  time  to  time  shed  and  renewed ; and,  probably,  the  same 
change  may  take  place,  though  more  gradually  and  less  perceptibly, 
on  other  ciliated  surfaces.  But  nothing  is  known  of  the  process  by 
which  this  is  effected. 

The  manner  in  which  the  cilia  move,  is  best  seen  when  they  are 
not  acting  very  briskly.  Most  generally  they  seem  to  execute  a sort 
of  fanning  or  lashing  movement ; and  when  a number  of  them  perform 
this  motion  in  regular  succession,  as  is  generally  the  case,  they  give 
rise  to  the  appearance  of  a series  of  waves  travelling  along  the  range 
of  cilia,  like  the  waves  caused  by  the  wind  in  a field  of  wheat.  When 
they  are  in  very  rapid  action,  the  undulation  is  less  obvious,  and,  as 

» Wagner’s  HandwOrterbuch  der  Phjsiologie,  art.  Flimmerbewegung. 


CILIATED  EPITHELIUM. 


67 


Henle  remarks,  their  motion  then  conveys  the  idea  of  swiftly-running 
water.  The  undulating  movement  may  be  beautifully  seen  on  the  gills 
of  a mussel,  and  on  the  arms  of  many  polypes.  The  undulations, 
with  some  exceptions,  seem  always  to  travel  in  the  same  direction  on 
the  same  parts.  The  impulsion,  also  which  the  cilia  communicate  to 
the  fluids  or  other  matters  in  contact  with  them,  maintains  a constant 
direction,  unless  in  certain  of  the  infusoria,  and  in  these  the  motion  has 
even  been  supposed  to  be  voluntary.  Thus,  in  the  windpipe  of  mam- 
malia, the  mucus  is  conveyed  upwards  towards  the  larynx,  and  if  a 
portion  of  the  membrane  be  detached,  matters  will  still  be  conveyed 
along  the  surface  of  the  separated  fragment  in  the  same  direction 
relatively  to  that  surface,  as  before  its  separation. 

The  persistence  of  the  ciliary  motion  for  some  time  after  death,  and 
the  regularity  with  which  it  goes  on  in  parts  separated  from  the  rest 
of  the  body,  sufficiently  prove  that,  with  the  possible  exceptions  alluded 
to,  it  is  not  under  the  influence  of  the  will  of  the  animal  nor  dependent 
for  iis  production  on  the  nervous  centres,  and  it  does  not  appear  to  be 
influenced  in  any  way  by  stimulation  or  sudden  destruction  of  these 
centres.  The  time  which  it  continues  after  death  or  separation  differs 
in  different  kinds  of  animals,  and  is  also  materially  influenced  by  tem- 
perature and  by  the  nature  of  the  fluid  in  contact  with  the  surface.  In 
warm-blooded  animals  the  period  varies  from  two  or  three  hours  to 
two  days,  or  even  more;  being  longer  in  summer  than  in  the  cold  of 
winter.  In  frogs  the  motion  may  continue  four  or  five  days  after  de- 
struction of  the  brain;  and  it  has  been  seen  in  the  gullet  of  the  tortoise 
fifieen  days  after  decapitation,  continuing  seven  days  after  the  muscles 
had  ceased  to  be  irritable. 

With  the  view  of  throwing  further  light  on  the  nature  of  this  re- 
markable kind  of  motion,  experiments  have  been  made  to  ascertain 
the  effect  produced  o'n  it  by  different  external  agents ; but  it  would 
seem  that,  with  the  exception  perhaps  of  moderate  heat  and  cold, 
these  agents  affect  the  action  of  the  cilia  only  in  so  far  as  they  act  de- 
structively on  their  tissue. 

The  effect  of  change  of  temperature  is  different  in  warm  and  cool-blooded  ani- 
mals. In  the  former  the  motion  is  stopped  by  a cold  of  43°  F.,  whereas  in  the 
frog  and  river-mussel,  it  goes  on  unimpaired  at  32°  F.  A moderately  elevated 
temperature,  say  100°  F.,  does  not  affect  the  motion  in  cold-blooded  animals,  but, 
of  course,  a heat  considerably  higher  than  this,  and  such  as  to  alter  the  tissue, 
would  put  an  end  to  it  in  all  cases.  Electric  shocks,  unless  they  cause  abrasion 
of  the  ciliated  surface,  (which  is  sometimes  the  case,)  produce  no  visible  effect ; 
and  the  same  is  true  of  galvanic  currents.  Fresh  water,  I find,  arrests  the  motion 
in  marine  mollusca  and  in  other  salt-water  animals  in  which  I have  tried  its 
effect , but  it  evidently  acts  by  destroying  both  the  form  and  substance  of  the  cilia, 
which  in  these  cases  are  adapted  to  a different  medium.  Most  of  the  common 
acid,  alkaline,  and  saline  solutions,  when  concentrated,  arrest  the  action  of  the 
cilia  instantaneously  in  all  animals;  but  dilution  delays  this  effect,  and  when  car- 
ried farther,  prevents  it  altogether ; and  hence  it  is,  probably,  due  to  a chemical 
alteration  of  the  tissue.  Narcotic  substances,  such  as  hydrocanic  acid,  salts  of 
morphia  and  strychnia,  opium  and  belladonna,  are  said  by  Purkinje  and  Valentin 
to  have  no  effect,  though  the  first-named  agent  has  certainly  appeared  to  me  to 
arrest  the  motion  in  the  river-mussel.  Bile  stops  the  action  of  the  cilia,  while 
blood  prolongs  it  in  vertebrated  animals ; but  the  blood  or  serum  of  the  vertebrata 
has  quite  an  opposite  effect  on  the  cilia  of  invertebrate  animals,  arresting  their 
motion  almost  instantaneously. 


68 


CILIATED  EPITHELIUM. 


It  must  be  confessed  that  the  nature  and  source  of  the  power  by 
which  the  cilia  act,  are  as  yet  unknown;  hut  whatever  doubt  may 
hangover  this  question,  it  is  plain  that  each  ciliated  cell  is  individually 
endowed  with  the  faculty  of  producing  motion,  and  that  it  possesses  in 
itself  whatever  organic  apparatus  and  whatever  physical  or  vital  pro- 
perty may  be  necessary  for  that  end  ; for  single  epithelium  cells  are 
seen  to  exhibit  the  phenomenon  long  after  they  have  been  completely 
insulated. 

Without  professing  to  offer  a satisfactory  solution  of  a question  beset  with  so 
much  difficulty,  it  seems,  nevertheless,  not  unreasonable  to  consider  the  ciliary 
motion  as  being  probably  a manifestation  of  that  property  on  which  the  more 
conspicuous  motions  of  animals  are  known  to  depend,  namely,  vital  contractility; 
and  this  view  has  at  least  the  advantage  of  referring  the  phenomenon  to  the  ope- 
ration o^a  vital  property,  already  recognised  as  a source  of  moving  power  in  the 
animal  body. 

It  is  true  that  nothing  resembling  a muscular  apparatus,  in  the  ordinary  sense 
of  the  term,  has  been  discovered  to  be  connected  with  the  cilia,  nor  is  it  neces- 
sary to  suppose  the  existence  of  any  such ; for  it  must  be  remembered  that  vital 
contractility  is  not  limited  to  a tissue  strictly  defined  in  its  appreciable  structure. 
The  anatomical  characters  of  voluntary  rtiuscle  differ  widely  from  those  of  most 
involuntary  contractile  textures,  although  the  movements  must  in  both  cases  be 
referred  to  the  same  principle.  The  heart  of  the  embryo  beats  while  yet  but  a 
mass  of  cells,  united,  to  all  appearance,  by  amorphous  matter,  in  which  no  fibres 
are  seen ; yet  no  one  would  doubt  that  its  motions  depend  then  on  the  same  pro- 
perty as  at  a later  period,  when  its  structure  is  fully  developed. 

In  its  persistence  after  systemic  death,  and  in  parts  separated  from  the  rest  of 
the  body,  the  ciliary  motion  agrees  with  the  motion  of  certain  muscular  struc- 
tures, as  the  heart  for  example ; and  the  agreement  extends  even  to  the  regular  or 
rhythmic  character  of  the  motion  in  these  circumstances.  It  is  true,  the  one  en- 
dures much  longer  than  the  other;  but  the  difference  appears  to  be  one  only  of 
degree,  for  differences  of  the  same  kind  are  known  to  prevail  among  muscles 
themselves.  No  one,  for  instance,  doubts  that  the  auricle  of  the  heart  is  mus- 
cular, because  it  beats  longer  after  death  than  the  ventricle ; nor,  because  a frog’s 
heart  continues  to  act  a much  longer  time  than  a quadruped’s,  is  it  inferred  that 
its  motion  depends  on  a power  of  a different  nature.  And  the  view  here  taken 
of  the  nature  of  the  ciliary  motion  derives  strength  from  the  consideration  that  the 
phenomenon  lasts  longest  in  cold-blooded  animals,  in  which  vital  contractility 
also  is  of  longest  endurance.  It  must  be  allowed,  unless  we  distrust  the  observa- 
tions of  very  competent  inquirers,  that  narcotic  substances  do  not  in  general  affect 
the  cilia,  while  they  are  generally  admitted  to  alter  or  extinguish  muscular 
action.  At  the  same  time  there  remains  some  ambiguity  on  this  head ; my  own 
observations  do  not  agree  in  all  points  with  those  referred  to,  and  Ehrenberg 
states  that  strychnia  produces  the  same  effect  on  the  cilia  of  infusoria  as  on  mus- 
cular organs.  Something,  moreover,  may  depend  on  the  facility  or  difficulty  with 
which  the  tissues  permit  the  narcotic  fluid  to  penetrate,  which  circumstance  must 
needs  affect  the  rapidity  and  extent  of  its  operation.  In  the  effect  of  opium  on 
the  heart  there  is  a great  difference,  according  as  the  narcotic  is  applied  to  its 
outer  or  its  inner  surface ; and  to  this  must  be  added  that  the  effect  of  narcotics 
has  not  been  carefully  tried  on  all  contractile  tissues.  Again,  we  see  differences 
in  the  mode  in  which  the  cilia  themselves  are  affected  by  the  same  agent ; thus 
fresh  water  instantly  arrests  their  motion  in  certain  cases,  while  it  has  no  such 
effect  in  others. 

The  discovery  lately  announced,*  that  vibrating  cilia  exist  on  the  ova  of  certain 
cryptogamic  vegetables,  may  perhaps  be  deemed  a strong  argument  on  the  oppo- 
site side  ; but  it  is  by  no  means  proved  that  the  sensible  motions  of  plants,  (such, 
at  least,  as  are  not  purely  physical,)  and  those  of  animals,  do  not  depend  on  one 
common  vital  property. 

* Unger.  Die  Pflanze  im  Momente  der  Theirwerdung.  Wien,  1843.  This  naturalist 
has  discovered  that  the  movements  of  the  sporidia  of  tlie  Vaiicliei  ia  Clavata  are  produced 
by  vibratile  cilia.  The  observation  has  since  been  confirmed  by  Siebold. 


PIGMENT. 


The  cells  of  the  cuticle,  and  of  other  textures  which  more  or  less 
resemble  it  in  structure,  sometimes  contain  a black  or  brown  matter, 
which  gives  a dark  colour  to  the  parts  over  which  these  cells  are 
spread.  A well-marked  example  of  such  pigment-cells  in  the  human 
body  is  afforded  by  the  black  coating  which  lines  the  choroid  mem- 
brane of  the  eye  and  covers  the  posterior  surface  of  the  iris.  They 
are  found  in  the  epidermis  of  the  negro  and  other  dark  races  of  man- 
kind, and  are  probably  present  in  the  more  dusky  parts  of  the  cuticle 
of  the  European.  They  have  been  found  also  on  certain  parts  of  the 
investing  membrane  (pia  materf  of  the  spinal  cord,  and  in  the  mem- 
branous labyrinth  of  the  ear. 

The  pigment  cells  of  the  choroid  membrane  (fig.  282)  are  for  the 
most  part  polyhedral  in  figure,  most  gene- 
rally six-sided,  and  connected  together  like 
the  pieces  of  a mosaic  pavement;  others  are 
spheroidal,  and  most  of  those  on  the  back  of 
the  iris  are  of  this  shape.  The  cells  contain 

called,  which  con- 
brown  granules  or 
)blong  shape, 

1 to i 

17000  24000 

These 


or 


Cells  from  pigmentum  nigrum ; 
a.  pigmentary  granules  conceal- 
ing the  nucleus;  b,  the  nucleus 
distitict  Magnified  410  diame- 
ters.— C.] 


the  pigment,  strictly  so 
sists  of  minute  black  or 
molecules  of  a round 
measuring  not  more  than  from 
of  an  inch  in  their  greatest  dimension 
molecules  are  densely  packed  together  in 
some  cells  ; in  others  they  are  more  scattered, 
and  then  it  may  be  seen  that  there  is  a cer- 
tain amount  of  colourless  matter  included 
along  with  them.  When  they  escape  from  the 
ruptured  cells,  they  exhibit  very  strikingly  the  molecular  movement. 
It  is  worthy  of  remark,  that  when  viewed  singly  with  a very  high 
magnifying  power  they  look  transparent  and  almost  colourless,  and  it 
is  only  when  they  are  heaped  together  that  their  blackness  distinctly 
appears.  The  cells  have  a colourless  nucleus,  which  is  very  generally 
hidden  from  view  by  the  black  particles.  It  contains  a central  nucle- 
olus. 

Examined  chemically,  the  black  matter  is  found  to  be  insoluble  in 
cold  and  hot  water,  alcohol,  ether,  fixed  and  volatile  oils,  acetic  and 
diluted  mineral  acids.  Its  colour  is  discharged  by  chlorine.  The 
pigment  of  the  bullock’s  eye,  w’hen  purified  by  boiling  in  alcohol  and 
ether,  was  found  by  Scherer  to  consist  of  58-672  carbon,  5-962  hydro- 
gen, 13-768  nitrogen,  and  21-598  oxygen;  its  proportion  of  carbon  is 
thus  very  large.  Preceding  chemists  had  obtained  from  its  ashes 
oxide  of  iron,  chloride  of  sodium,  lime,  and  phosphate  of  lime. 


70 


PIGMENT. 


[Fig.  283. 


The  dark  colour  of  the  negro  is  known  to  have  its  seat  in  the 
cuticle,  and  chielly  in  the  deeper  and  softer  part  [fig.  283,  a,]  named 
the  rete  mucosum.  According  to  Henle,  it  is  caused  by  the  presence 
ot  pigment  cells,  resembling  those  of  the  choroid  in  almost  every 

respect  save  their  size,  w'hich  is  somewhat 
less.  These  are  intermixed  with  colourless 
cells,  and  on  the  proportion  of  the  two  the 
depth  of  colour  of  different  parts  depends. 
According  to  the  same  authority,  the  darker 
parts  of  the  European  skin  owe  their  colour 
to  pigment  cells  like  those  of  the  negro,  only 
still  smaller  in  size,  less  defined  in  their  out- 
line, and  less  numerous.  Krause  affirms  that 
the  dark  colour  of  the 
negro  and  white  races 
the  presence  of  cells 
brown  nuclei,  the  substance  of  the  cell  being 
also  tinged,  but  less  deeply  than  the  nucleus, 
and  the  colour  being  diffused  through  the  mass  and  not  caused  by 
molecules.  He  admits  that  a few  true  pigment  cells  exist  in  the 
negro’s  skin.  But  whatever  be  the  structure  of  the  colouring  parti- 
cles, it  cannot  be  doubted  that  in  the  skin  the  matter  is  the  same  in  its 
essential  nature  as  in  the  choroid.  In  albino  individuals,  both  of  the 
negro  and  European  races,  in  whom  the  black  matter  of  the  choroid 
is  wanting,  the  cuticle  and  the  hair  are  colourless  also. 


Vertical  section  of  the  cuticle, 
from  the  scrotum  of  a negro,  a. 
Deep  cells,  loaded  with  pigment. 
b.  Cells  at  a higlier  level,  paler 
and  more  flattened,  c.  Cells  at 
the  surface,  scaly  and  colourless 
as  in  the  white  races.  Magnified 
300  diameters. — Todd  and  Bow- 
man,] 


cuticle  both  of  the 
depends  chiefly  on 
which  have  dark 


In  some  situations  the  pigment  cells  become  irregular  and  jagged 
at  their  edges,  or  even  branch  out  into  long  irregular  processes.  Such 
ramified  cells  are  very  common  in  many  animals,  as  those  from  the 
skin  of  the  frog  represented  in  vol.  i.  fig.  16.  In  the  human  body  pig- 
ment cells  of  this  description  are  found  in  the  dark  cellular  membrane 
between  the  sclerotic  and  choroid  coats  of  the  eye,  and  on  the  pia 
mater  covering  the  upper  part  of  the  spinal  cord.  The  condition  of 
the  pigment  in  the  hairs  will  be  afterwards  described. 

From  the  observations  of  Valentin  on  the  choroid  membrane  of  the 
embryo  bird,  it  appears  that  the  pigment  cells  are  formed  round  pre- 
viously existing  nuclei,  and  that  they  are  at  first  colourless,  but  that 
black  molecules  subsequently  appear  in  them,  first  immediately  round 
the  nucleus,  and  afterwards  throughout  the  rest  of  the  cell. 

When  the  cuticle  of  the  negro  is  removed  by  means  of  a blister,  it 
is  renewed  again  of  its  original  dark  hue ; but  if  the  skin  be  destroyed 
to  any  considerable  depth,  as  by  a severe  burn,  tbe  resulting  scar 
remains  long  white,  though  it  at  length  acquires  a dark  colour. 


In  the  eye  the  black  matter  seems  obviously  intended  to  absorb  redundant  light, 
and  accordingly  its  absence  in  albinos  is  attended  with  a difficulty  of  bearing  a 
light  of  considerable  brightness.  Its  uses  in  other  situations  are  not  so  apparent. 
The  pigment  of  the  cuticle,  it  has  been  supposed,  may  screen  the  subjacent  cutis 
from  the  pungency  of  the  sun’s  rays.  In  many  animals  the  pigment  is  not  only 
employed  to  variegate  the  surface  of  the  body,  but  attaches  itself  to  deep-seated 
parts.  Thus,  in  the  frog  the  branches  and  twigs  of  the  blood-vessels  are  speckled 
over  with  it,  and  in  many  fish  it  imparts  a black  colour  to  the  peritoneum  and 
other  internal  membranes. 


ADIPOSE  TISSUE. 


The  human  body  in  the  healthy  state  contains  a considerable  amount 
of  fatty  matter  of  different  kinds.  Fat,  as  already  mentioned,  is  found 
in  the  blood  and  chyle,  and  in  the  lymph,' but  much  more  sparingly. 
It  exists,  too,  in  several  of  the  secretions,  in  some  constituting  the 
chief  ingredient;  and  in  one  or  other  of  its  modifications  it  enters  into 
the  composition  of  certain  solid  textures.  But  by  far  the  greater  part 
of  the  fat  of  the  body  is  inclosed  in  small  cells  or  vesicles,  which, 
together  with  their  contained  matter,  constitute  the  adipose  tissue. 

This  tissue  is  not  confined  to  any  one  region  or  organ,  but  exists 
very  generally  throughout  the  body,  accompanying  the  still  more 
widely-distributed  cellular  or  areolar  tissue  in  most  though  not  in  all 
parts  in  which  the  latter  is  found.  Still,  its  distribution  is  not  uniform, 
and  there  are  certain  situations  in  which  it  is  collected  more  abun- 
dantly. It  forms  a considerable  layer  underneath  the  skin,  and,  toge- 
ther with  the  subcutaneous  cellular  tissue  in  which  it  is  lodged,  con- 
stitutes in  this  situation  what  has  been  called  the  fanniculus  adiposus. 
It  is  collected  in  large  quantity  round  certain  internal  parts,  especially 
the  kidneys.  It  is  seen  filling  up  the  furrows  on  the  surface  of  the 
heart,  and  imbedding  the  vessels  of  that  organ  underneath  its  serous 
covering ; and  in  various  other  situations  it  is  deposited  beneath  the 
serous  membranes,  or  is  collected  between  their  folds  as  in  the  mesen- 
tery and  omentum,  at  first  generally  gathering  along  the  course  of  the 
blood-vessels,  and  at  length  accumulating  very  copiously.  Collections 
of  fat  are  also  common  round  the  joints,  lying  on  the  outer  surface  of 
the  synovial  membrane,  and  filling  up  inequalities;  in  many  cases,  like 
the  fat  in  the  omentum,  lodged  in  folds  of  the  membrane  which  project 
into  the  articular  cavity.  Lastly,  the  fat  exists  in  large  quantity  within 
the  bones,  where  it  forms  the  marrow.  There  are  some  parts  in  which 
fat  is  never  found  in  the 
healthy  condition  of  the 
body.  Thus  it  does  not 
exist  in  the  subcutaneous 
cellular  tissue  of  the  eye- 
lids, penis,  or  scrotum,  nor 
in  the  lungs,  nor  within  the 
cavity  of  the  cranium. 

When  subjected  to  the 
microscope,  the  adipose 
tissue  (fig.  284)  is  seen 
to  consist  of  minute  ve- 
sicles, filled  with  an  oily 
matter,  and  for  the  most 
part  lodged  in  the  meshes 
of  the  areolar  tissue.  The 


Fig.  284. 


A small  cluster  of  fat-cells  magnified  150  diameters. 


72 


ADIPOSE  TISSUE. 


vesicles  are  most  commonly  collected  into  little  lobular  clusters,  and 
these  again  into  the  little  lumps  of  fat  which  we  see  with  the  naked 
6}e,  and  which  in  some  parts  are  aggregated  into  round  or  irregu- 
lar masses  of  considerable  magnitude.  Sometimes  the  vesicles,  though 
grouped  together,  have  less  of  a clustered  arrangement,  as  when 
they  collect  alongside  of  the  minute  blood-vessels  of  thin  membranous 
structures. 

The  vesicles  or  fat-cells  are  round  or  oval,  unless  where  packed 
closely  together,  in  which  case  they  acquire  an  angular  figure,  and 
bear  a striking  resemblance  to  the  cells  of  vegetable  tissues.  The 
greater  number  of  them  are  from  to  of  an  inch  in  diameter, 
but  may  exceed  or  fall  short  of  this  measurement.  Each  one  consists 
of  a very  delicate  envelope,  enclosing  the  oily  matter.  The  envelope 
is  generally  quite  transparent,  and  appears  to  be  homogeneous  in 
structure,  though  in  some  cases  its  aspect  is  very  faintly  granular. 
Schwann  discovered  a nucleus  in  the  fat-cells  of  the  embryo;  the 
nucleus  contains  one  or  two  nucleoli,  and  is  attached  to  the  inside  of 
the  cell-wall  or  imbedded  in  its  substance  ; it  is  rarely  found  in  cells  of 
later  periods. 

The  oily  matter  contained  in  the  cells  is  liquid,  but  in  fat  taken  from 
the  human  body  after  death  many  of  the  cells  present  a stellated 
crystalline  spot  in  their  interior,  as  if  a partial  solidification  had  taken 
place ; this  may  be  due  to  separation  and  deposit  of  margarine,  the 
solid  constituent  of  human  fat.  The  chemical  nature  of  fat  has  been 
already  explained  (vol.  i.  p,  47). 


[Fig.  285. 


Blood-vessels  of  Fat: — 1.  Minute  flattened  fat-lobule,  in  which  the  vessels  only  are  represented. 
3.  The  terminal  artery.  4.  The  primitive  vein.  5.  The  fat  vesicles  of  one  border  of  the  lohnie, 
separately  represented.  Magnified  100  diamelers.— 2.  Plan  of  the  arrangement  of  the  capillaries 
on  the  exterior  of  the  vesicles:  more  highly  magnified. — Todd  and  Bowman.] 

The  fat  being  thus  contained  in  closed  cells,  it  will  be  readily  under- 
stood why,  though  liquid  or  nearly  so  in  the  living  body,  it  does  not 
shift  its  place  in  obedience  to  pressure  or  gravitation,  as  happens  with 


ADIPOSE  TISSUE. 


73 


the  water  of  dropsy  and  other  fluids  effused  into  the  interstices  of  the 
cellular  tissue;  such  fluids,  being  unconfined,  of  course  readily  pass 
from  one  place  to  anolher  through  the  open  areolte. 

The  cellular  tissue  connects  and  surrounds  the  larger  lumps  of  fat, 
but  forms  no  special  envelope  to  the  smaller  clusters;  and  although 
fine  fasciculi  and  filaments  of  that  tissue  pass  irregularly  over  and 
through  the  clusters,  yet  it  is  probable  that  the  vesicles  are  held  toge- 
ther in  these  groups  mainly  by  the  fine  network  of  capillary  vessels 
distributed  to  them.  In  the  marrow  the  cellular  tissue  is  v^ery  scanty; 
indeed  the  fat-cells  in  some  parts  of  the  bones  are  said  to  be  altogether 
unaccompanied  by  cellular  filaments. 

The  adipose  tissue  is  copiously  supplied  with  blood-vessels  [fig. 
286.]  The  larger  branches  of  these  pass  into  the  fat  lumps,  where 
they  then  run  between  the  lobules  and  subdivide,  till  at  length  a little 
artery  and  vein  are  sent  to  each  small  lobule,  dividing  into  a network 
of  capillary  vessels,  which  not  only  surrounds  the  cluster  externally, 
but  passes  through  between  the  vesicles  in  all  directions,  supporting 
and  connecting  them.  The  lymphatics  of  the  fat,  if  it  really  possesses 
any,  are  unknown.  Nor  have  nerves  been  seen  to  terminate  in  it, 
though  nerves  destined  for  other  textures  may  pass  through  it.  Accord- 
ingly it  has  been  observed  that,  unless  when  such  traversing  nervous 
twigs  happen  to  be  encountered,  a puncturing  instrument  may  be 
carried  through  the  adipose  tissue  without  occasioning  pain. 

As  to  the  uses  of  the  fatty  tissue,  it  may  be  observed,  in  the  first  place,  that  it 
serves  the  merely  mechanical  purpose  of  a light,  soft,  and  elastic  packing  mate- 
rial to  fill  vacuities  in  the  body.  Being  thus  deposited  between  and  around 
different  organs,  it  affords  them  support,  facilitates  motion,  and  protects  them 
from  the  injurious  effects  of  pressure.  In  this  way,  too,  it  gives  to  the  exterior 
of  the  body  its  smooth  rounded  contour.  Further,  being  a bad  conductor  of  heat, 
the  subcutaneous  fat  must  so  far  serv'e  as  a means  of  retaining  the  warmth  of  the 
body,  especially  in  warm-blooded  creatures  exposed  to  great  external  cold,  as 
the  whale  and  other  cetaceous  animals,  in  which  it  forms  a very  thick  stratum, 
and  must  prove  a much  more  effectual  protection  than  a covering  of  fur  in  a 
watery  element. 

But  the  most  important  use  of  the  fat  consists  in  its  subserviency  to  the  process 
of  nutrition.  Composed  chiefly  of  carbon  and  hydrogen,  it  is  absorbed  into  the 
blood  and  consumed  in  respiration,  combining  with  oxygen  to  form  carbonic 
acid  and  water,  and  thus  contributing  with  other  hydrocarbon ous  matters  to 
maintain  the  heat  of  the  body ; and  it  is  supposed  that  when  the  digestive  pro- 
cess introduces  into  the  system  more  carbon  and  hydrogen  than  is  required  for 
immediate  consumption,  the  excess  of  these  elements  is  stored  up  in  the  form  of 
fat,  to  become  available  for  use  when  the  expenditure  exceeds  the  immediate 
supply.  According  to  this  view,  active  muscular  exercise,  which  increases  the 
respiration,  tends  to  prevent  the  accumulation  of  fat  by  increasing  the  consump- 
tion of  the  hydrocarbonous  matter  introduced  into  the  body.  Again,  when  the 
direct  supply  of  calorific  matter  for  respiration  is  diminished  or  cut  off  by  with- 
holding food,  or  by  interruption  of  the  digestive  process,  nature  has  recourse  to 
that  which  has  been  reserved  in  the  form  of  fat;  and  in  the  wasting  of  the  body 
caused  by  starvation,  the  fat  is  the  part  first  consumed. 

The  use  of  the  fat  in  nutrition  is  well  illustrated  by  what  occurs  in  the  hedge- 
hog and  some  other  hybemating  animals.  In  these  the  function  of  alimentation 
is  suspended  during  their  winter  sleep,  and  though  their  respiration  is  reduced  to 
the  lowest  amount  compatible  with  life,  and  their  temperature  falls,  there  is  yet 
a considerable  amount  of  hydrocarbonous  material  provided  in  the  shape  of  fat 
before  their  hybernation  commences,  to  be  slowly  consumed  during  that  period, 

VOL.  II.  7 


74 


ADIPOSE  TISSUE. 


or  perhaps  to  afford  an  immediate  supply  on  their  respiration  becoming  again 
active  in  spring. 

It  has  been  estimated  that  the  mean  quantity  of  fat  in  the  human  subject  is 
about  one-twentieth  of  the  weight  of  the  body,  but  from  what  has  been  said,  it 
is  plain  that  the  amount  must  be  subject  to  great  fluctuation.  The  proportion  is 
usually  greatest  about  the  middle  period  of  life,  and  greatly  diminishes  in  old 
age.  High  feeding,  repose  of  mind  and  body,  and  much  sleep,  favour  the  pro- 
duction of  fat.  To  these  causes  must  be  added  individual  and  perhaps  heredi- 
tary predisposition.  There  is  a greater  tendency  to  fatness  in  females  than 
males,  also,  it  is  said,  in  eunuchs.  The  effect  of  castration  in  promoting  the 
fattening  of  domestic  animals  is  weU  known. 

In  infancy  and  childhood  the  fat  is  confined  chiefly  to  the  subcutaneous  tissue. 
In  after  life  it  is  more  equally  distributed  through  the  body,  and  in  proportion- 
ately greater  quantity  about  the  viscera.  In  Hottentot  females,  fat  accumulates 
over  the  gluteal  muscles,  forming  a considerable  prominence,  and  in  a less  degree 
over  the  deltoid ; a tendency  to  local  accumulation  of  the  subcutaneous  fat  is 
known  to  exist  also  in  particular  races  of  quadrupeds. 

Development. — According  to  Valentin,  the  fat  first  appears  in  the 
human  embryo  about  the  fourteenth  week  of  intra-uterine  life.  At 
this  period  the  fat-cells  are  insulated,  but  by  the  end  of  the  fifth  month 
they  are  collected  into  small  groups.  When  first  seen,  they  are  also 
of  comparatively  small  size.  As  already  stated,  the  fcetal  fat-cells 
contain  a nucleus  in  their  early  condition,  which  afterwards  disap- 
pears ; but  it  is  not  certain  that  the  nucleus  precedes  and  gives  rise  to 
the  cell. 

It  has  been  a question  whether,  when  the  fat  undergoes  absorption,  the  vesi- 
cles are  themselves  consumed  along  with  their  contents.*  Dr.  W.  Hunter 
believed  that  they  still  remained  after  being  emptied  • he  was  led  to  this  opinion 
by  observing  the  condition  of  the  cellular  tissue  in  dropsical  bodies  from  which 
the  fat  had  disappeared,  there  being  in  such  cases  a rharked  difference  in  aspect 
between  the  parts  of  that  tissue  which  had  originally  contained  fat  and  those 
which  had  not,  which  difference  he  attributed  to  the  persistence  of  the  empty 
fat  vesicles.  Gurlt  states  that  the  fat-cells  in  emaciated  animals  are  filled  with 
serum. 

* [In  the  rete  of  insects,  during  the  larva  state,  exist  numerous  fat  vesicles  distended 
with  oil,  but  which  in  the  imago,  are  distinctly  seen  in  the  same  position  and  contain  no 
oil,  which  has  apparently  been  displaced  by  a serous  fluid. — J.  L.] 


SEROUS  MEMBRANES. 


The  serous  membranes  are  so  named  from  the  nature  of  the  fluid 
with  which  their  surface  is  moistened.  They  line  cavities  of  the  body 
which  have  no  outlet,  and  the  chief  examples  of  them  are,  the  perito- 
neum, the  largest  of  all,  lining  the  cavity  of  the  abdomen ; the  two 
pleuree  and  pericardium  in  the  chest ; the  arachnoid  membrane  in  the 
cranium  and  vertebral  canal ; and  the  tunica  vaginalis  surrounding 
each  of  the  testicles  within  the  scrotum. 

Form  and  arrangement. — In  all  these  cases  the  serous  membrane 
has  the  form  of  a closed  sac,  one  part  of  which  is  applied  to  the  walls 
of  the  cavity  which  it  lines,  the  parietal  portion ; whilst  the  other  is 
reflected  over  the  surface  of  the  organ  or  organs  contained  in  the 
cavity,  and  is  therefore  named  the  reflected  or  visceral  portion  of  the 
membrane.  Hence  the  viscera  in  such,  cavities  are  not  contained 
wiihin  the  sac  of  the  serous  membrane,  but  are  really  placed  behind 
or  outside  of  it ; merely  pushing  inwards,  as  it  were,  the  part  of  the 
membrane  which  immediately  covers  them,  some  organs  receiving  in 
this  way  a complete,  and  others  but  a partial  and  sometimes  a very 
scanty  investment. 

In  passing  from  one  part  to  another,  the  membrane  frequently  forms 
folds  which  in  general  receive  the  appellation  of  ligaments,  as,  for 
example,  the  folds  of  peritoneum  passing  between  the  liver  and  the 
parietes  of  the  abdomen,  but  which  are  sometimes  designated  by  spe- 
cial names,  as  in  the  instances  of  the  mesentery,  mesocolon  and  omen- 
tum. 

The  peritoneum,  in  the  female  sex,  is  an  exception  to  the  rule 
that  serous  membranes  are  perfectly  closed  sacs,  inasmuch  as  it  has 
two  openings  by  which  the  Fallopian  tubes  communicate  with  its 
cavity. 

A serous  membrane  sometimes  lines  a fibrous  membrane,  as  where 
the  arachnoid  lines  the  dura  mater,  or  where  the  serous  layer  of  the 
pericardium  adheres  to  its  outer  or  fibrous  part.  Such  a combination 
is  often  named  a flbro-serous  membrane. 

The  inner  surface  of  a serous  membrane  is  free,  smooth,  and 
polished ; and,  as  would  occur  with  an  empty  bladder,  the  inner  sur- 
face of  one  part  of  the  sac  is  applied  to  the  corresponding  surface  of 
some  other  part ; a small  quantity  of  fluid,  usually  not  more  than 
merely  moistens  the  contiguous  surfaces,  being  interposed.  The  parts 
situated  in  a cavity  lined  by  serous  membrane,  can  thus  glide  easily 
against  its  parietes  or  upon  each  other,  and  their  motion  is  rendered 
smoother  by  the  lubricating  fluid. 

The  outer  surface  most  commonly  adheres  to  the  parts  which  it 
lines  or  covers,  the  connexion  being  effected  by  means  of  cellular  or 
areolar  tissue,  named  therefore  “ subserous,”  which,  when  the  mem- 


76 


SEROUS  MEMBRANES. 


brane  is  detached,  gives  to  its  outer  and  previously  adherent  surface 
a flocculent  aspect.  The  degree  of  firmness  of  the  connexion  is  very 
various  : in  some  parts,  the  membrane  can  scarcely  be  separated  ; in 
others,  its  attachment  is  so  lax  as  to  permit  of  easy  displacement. 
The  latter  is  the  case  in  the  neighbourhood  of  the  openings  through 
M'hich  abdominal  hernise  pass,  and  accordingly  "wdien  such  protrusions 
of  the  viscera  happen  to  take  place,  they  usually  push  the  peritoneum 
before  them  in  form  of  a hernial  sac. 

The  visceral  portion  of  the  arachnoid  membrane  is  in  some  measure 
an  exception  to  the  rule  of  the  outer  surface  being  every  where  adhe- 
rent; for,  in  the  greater  part  of  its  extent,  it  is  thrown  loosely  round 
the  parts  which  it  covers,  a few  fine  fibrous  bands  being  the  sole  bond 
of  connexion  ; and  a quantity  of  serous  fluid  is  interposed,  especially 
in  the  vertebral  canal  and  base  of  the  cranium,  between  it  and  the  pia 
mater,  which  is  the  membrane  immediately  investing  the  brain  and 
spinal  cord. 

Structure  and  'properties. — Serous  membranes  are  thin  and  transpa- 
rent, so  that  the  colour  of  subjacent  parts  shines  through  them.  They 
are  tolerably  strong,  with  a moderate  degree  of  extensibility  and  elas- 
ticity. They  consist  of  1st,  a simple  layer  of  scaly  epithelium,  already 
described  and  figured  (page  60,  fig.  274),  which,  however,  is  ciliated 
on  the  serous  membrane  lining  the  ventricles  of  the  brain,  and  on  the 
part  of  the  peritoneum  which  covers  the  fimbriated  end  of  the  Fallo- 
pian tubes  ; 2dly,  next  to  the  epithelium,  and  supporting  it,  an  ex- 
ceedingly fine  lamella  of  simple  or  homogeneous  membrane,  named  base- 
ment membrane  by  Todd  and  Bowman,  who,  as  far  as  I know,  were 
the  first  distinctly  to  point  it  out  as  a constituent  of  the  serous  mem- 
branes; and,  3dly,  one  or  more  layers  of  fine  but  dense  cellular  or 
areolar  tissue.  This  consists,  as  usual,  of  bundles  of  white  filaments 
mixed  with  elastic  fibres : the  former,  when  there  are  two  or  more 
layers,  take  a different  direction  in  different  planes ; the  latte*"  unite 
into  a network,  and,  in  many  serous  membranes,  as  remarked  by 
Henie,  are  principally  collected  into  a reticular  layer  at  the  surface  of 
the  strata  of  cellular  tissue,  or,  to  speak  more  precisely,  immediately 
beneath  the  basement  membrane.  The  constituent  cellular  tissue  of 
the  serous  membrane,  is  of  course  continuous  with  the  usually  more 
lax  subserous  cellular  tissue  connecting  the  membrane  to  the  subjacent 
parts. 

Blood-vessels,  ending  in  a capillary  network  with  comparatively 
wide  meshes,  together  with  plexuses  of  lymphatic  vessels,  pervade  the 
subserous  tissue  and  the  cellular  tissue  which  forms  part  of  the  serous 
membrane,  but  do  not  penetrate  its  basement  membrane  or  epithelium. 
Plexuses  of  fine  nervous  fibres  have  been  described  by  several  anato- 
mists, in  or  immediately  beneath  the  serous  membranes  of  various 
regions  ; nevertheless,  it  would  seem,  that  when  in  a healthy  condition, 
these  membranes  possess  little  or  no  sensibility : they  are  altogether 
devoid  of  vital  contractility. 

Fluid. — The  internal  surface  of  serous  cavities  is  moistened  and  lubricated  with 
a transparent  and  nearly  colourless  fluid,  which  in  health  exists  only  in  a very 
small  quantity.  This  fluid,  which  is  doubtless  derived  from  the  blood-vessels  of 
the  membrane,  is  commonly  understood  to  be  similar  in  constitution  to  the  serum 


SEROUS  MEMBRANES. 


77 


of  the  blood,  and  such  unquestionably  is  generally  its  nature  when  it  accumulates 
in  unusually  large  quantity,  as  in  dropsical  effusions,  the  chief  or  only  difference 
being  in  its  proportion  of  albumen,  which  is,  for  the  most  part,  smaller  than  in 
blood-serum.  But  it  was  long  since  remarked  by  Hewson  (and  a similar  opinion 
seems  to  have  been  held  by  HaUer  and  Monro),  that  the  fluid  obtained  from  the 
serous  cavities  of  recently  killed  animals  coagulates  spontaneously,  and  thus  re- 
sembles the  lymph  of  the  lymphatic  vessels,  and,  we  may  add,  the  liquor  san- 
guinis or  plasma  of  the  blood,  the  coagulation  being,  of  course,  due  to  fibrin. 
Hewson  found  that  the  coagulability  diminished  as  the  quantity  of  the  fluid 
increased.  In  confirmation  of  Hewson’s  statement,  I may  mention  that  I have 
always  found  the  fluid  obtained  from  the  peritoneal  cavity  of  rabbits  to  coagu- 
late spontaneously  in  a greater  or  less  degree.  Hewson  made  his  observations 
on  the  fluid  of  the  peritoneum,  pleura,  and  pericardium,  in  various  animals,  viz., 
bullocks,  dogs,  geese,  and  rabbits.  The  subject  needs  further  examination,  for 
we  know  that  the  small  quantity  of  liquid  which  may  generally  be  obtained  from 
the  human  pericardium  after  death  is  not  observed  to  contain  a coagulum  nor  to 
coagulate  on  exposure.* 

When  a serous  membrane  is  inflamed,  it  has  a great  tendency  to  throw  out 
coagulable  l)mph  (or  fibrin)  and  serum,  the  two  constituents  of  the  blood  plasma, 
the  former  chiefly  adhering  to  the  inner  surface  of  the  membrane,  whilst  the 
latter  gathers  in  its  cavity.  The  coagulable  lymph  spread  over  the  surface,  in 
form  of  a “false  membrane,”  as  it  is  called,  or  agglutinating  the  opposed  sur- 
faces of  the  serous  sac  and  causing  adhesion,  becomes  pervaded  by  blood-vessels, 
and  in  process  of  time  converted  into  cellular  tissue. 

Breaches  of  continuity  in  these  membranes  are  readily  repaired,  and  the  new- 
formed  portion  acquires  all  the  characters  of  the  original  tissue. 

* See  Hewson’s  Works,  published  by  the  Sydenham  Society,  p.  157,  with  some  impor- 
tant remarks  in  notes  xviii.  and  Ixviii,  by  the  editor,  Mr.  Gulliver. 


7* 


MUCOUS  MEMBRANES. 


These  membranes,  unlike  the  serous,  line  internal  passages  and  other 
cavities  which  open  on  the  surface  of  the  body,  as  well  as  various 
recesses,  sinuses,  gland-ducts  and  receptacles  of  secretion,  w'hich  open 
into  such  passages.  They  are  habitually  subject  to  the  contact  of 
foreign  substances  introduced  into  the  body,  such  as  air  and  aliment, 
or  of  various  secreted  or  excreted  matters,  and  hence  their  surface  is 
coated  over  and  protected  by  mucus,  a fluid  of  a more  consistent  and 
tenacious  character  than  that  which  moistens  the  serous  membranes. 

The  mucous  membranes  of  several  different  or  even  disthnt  parts 
are  continuous,  and,  with  certain  unimportant  reservations,  to  be  after- 
wards explained,  they  may  all  be  reduced  to  two  great  divisions, 
namely,  the  gastro-pulmonary  and  the  genito-urinary.  The  former 
covers  the  inside  of  the  alimentary  and  air  passages  as  well  as  the  less 
considerable  cavities  communicating  with  them.  It  may  be  described 
as  commencing  at  the  edges  of  the  lips  and  nostrils  where  it  is  con- 
tinuous with  the  skin,  and  proceeding  through  the  nose  and  mouth  to 
the  throat,  whence  it  is  continued  throughout  the  whole  length  of  the 
alimentary  canal  to  the  termination  of  the  intestine,  there  again  meet- 
ing the  skin,  and  also  along  the  windpipe  and  its  numerous  divisions 
as  far  as  the  air-cells  of  the  lungs,  to  which  it  affords  a lining.  From 
the  nose  the  membrane  may  be  said  to  be  prolonged  into  the  lachrymal 
passages,  extending  up  the  nasal  duct  into  the  lachrymal  sac  and 
along  the  lachrymal  canals  until,  under  the  name  of  the  conjunctival 
membrane,  it  spreads  over  the  fore  part  of  the  eyeball  and  inside  of 
the  eyelids,  on  the  edges  of  which  it  encounters  the  skin.  Other  offsets 
from  the  nasal  part  of  the  membrane  line  the  frontal,  ethmoidal,  sphe- 
noidal, and  maxillary  sinuses,  and  from  the  upper  part  of  the  pharynx 
a prolongation  extends  on  each  side  along  the  Eustachian  tube  to  line 
that  passage  and  the  tympanum  of  the  ear.  Besides  these  there  are 
offsets  from  the  alimentary  membrane  to  line  the  lachrymal,  salivary, 
pancreatic,  and  biliary  ducts  and  the  gall-bladder.  The  genito-uri- 
nary membrane  invests  the  inside  of  the  urinary  bladder  and  the  whole 
track  of  the  urine  in  both  sexes,  from  the  interior  of  the  kidneys  to  the 
orifice  of  the  urethra,  also  the  seminal  ducts  and  vesicles  in  the  male, 
and  the  vagina,  uterus,  and  Fallopian  tubes  in  the  female. 

The  mucous  membranes  lining  the  ducts  of  the  mammary  glands, 
being  unconnected  with  either  of  the  above-mentioned  great  tracts, 
have  sometimes  been  enumerated  as  a third  division,  and  the  number 
might  of  course  be  multiplied,  were  we  separately  to  reckon  the  mem- 
branes prolonged  from  the  skin  into  the  ducts  of  the  numerous  little 
glands  which  open  on  the  surface  of  the  body. 

The  mucous  membranes  are  attached  by  one  surface  to  the  parts 
which  they  line  or  cover  by  means  of  areolar  tissue,  named  “submu- 
cous,” which  differs  greatly  in  quantity  as  well  as  in  consistency  in 


MUCOUS  MEMBRANES. 


79 


different  parts.  The  connexion  is  in  some  cases  close  and  firm,  as  in 
the  cavity  of  the'  nose  and  its  adjoining  sinuses ; in  other  instances, 
especially  in  cavities  subject  to  frequent  variation  in  capacity,  like  the 
gullet  and  stomach,  it  is  lax  and  allo'ws  of  some  degree  of  shifting  of 
the  connected  surfaces.  In  such  cases  as  the  last-mentioned,  the  mu- 
cous membrane  is  accordingly  thrown  into  folds,  when  the  cavity  is 
narrowed,  by  contraction  of  the  exterior  coat  of  the  organ,  and  of 
course  these  folds,  or  rugoB,  as  they  are  named,  are  effaced  by  disten- 
sion. But  in  certain  parts  the  mucous  membrane  forms  permanent 
folds,  not  capable  of  being  thus  effaced,  which  project  conspicuously 
into  the  cavity  which  it  lines.  The  best  marked  example  ot  these  is 
presented  by  the  valvulce  conniventes  seen  in  the  small  intestine.  These, 
as  is  more  fully  described  in  the  special  anatomy  of  the  intestines,  are 
crescent-shaped  duplicatures  of  the  membrane,  with  connecting  cellu- 
lar tissue  betw'een  their  laminse,  which  are  placed  transversely  and 
follow  one  another  at  very  short  intervals  along  a great  part  of  the 
intestinal  tract.  The  chief  purpose  of  the  valvulse  conniventes  is 
doubtless  to  increase  the  surface  of  the  absorbing  mucous  membrane 
within  the  cavity,  and  it  has  also  been  supposed  that  they  serve 
mechanically  to  delay  the  alimentary  mass  in  its  progress  down- 
wards. A mechanical  office  has  also  been  assigned  to  a series  of 
oblique  folds  of  a similar  permanent  kind,  though  on  a smaller  scale, 
which  exist  within  the  cystic  duct. 

Physical  properties. — In  most  situations  the  mucous  membranes  are 
nearly  opaque  or  but  slightly  translucent.  They  possess  no  great 
degree  of  tenacity  and  but  little  elasticity,  and  hence  are  readily  torn 
by  a moderate  force.  As  to  colour,  they  cannot  be  said  intrinsically 
to  have  any,  and  when  perfectly  deprived  of  blood  they  accordingly 
appear  white  or  at  most  somewhat  gray.  The  redness  which  they 
commonly  exhibit  during  life,  and  retain  in  greater  or  less  degree  in 
various  parts  after  death,  is  due  to  the  blood  contained  in  their  vessels, 
although  it  is  true  that  after  decomposition  has  set  in,  the  red  matter 
of  the  blood,  becoming  dissolved,  transudes  through  the  coats  of  the 
vessels,  and  gives  a general  red  tinge  to  the  rest  of  the  tissue.  The 
degree  of  redness  exhibited  by  the  mucous  membrane  after  death  is 
greater  in  the  foetus  and  infant  than  in  the  adult.  It  is  greater  too  in 
certain  situations ; thus,  of  the  different  parts  of  the  alimentary  canal, 
it  is  most  marked  in  the  stomach,  pharynx,  and  rectum.  Again,  the 
intensity  of  the  tint,  as  well  as  its  extent,  is  influenced  by  circumstances 
accompanying  or  immediately  preceding  death.  Thus  the  state  of 
inflammation  or  the  local  application  of  stimuli  to  the  membrane,  such 
as  irritant  poisons,  or  even  food,  in  the  stomach,  is  apt  to  produce 
increased  redness;  and  all  the  mucous  membranes  are  liable  to  be 
congested  with  blood  and  suffused  with  redness  when  death  is  imme  ■ 
diately  preceded  by  obstruction  to  the  circulation,  as  in  cases  of 
asphyxia,  and  in  many  diseases  of  the  heart. 

Structure. — A mucous  membrane  is  composed  of  the  corium  and 
epithelium.  The  epithelium  covers  the  surface  and  has  already  been 
described  (p.  58).  The  membrane  which  remains  after  removal  of 
the  epithelium  is  named  the  corium,  as  in  the  analogous  instance  of  the 


80 


MUCOUS  MEMBRANES. 


true  skin.  The  corium  may  be  said  to  consist  of  a fibro-vascular 
layer,  of  variable  thickness,  bounded  superficially  or  next  the  epithelium 
by  an  extremely  fine  transparent  lamella,  named  basement  membrane 
by  Bowman,  and  primary  membrane,  limitary  membrane,  and  mem- 
brana  propria  by  others  who  have  described  it.  It  must  be  explained, 
however,  that  these  two  constituents  of  the  corium  cannot  in  all  situa- 
tions be  separated  from  each  other,  nor  indeed  can  the  presence  of 
botli  be  pi'oved  by  actual  demonstration  in  all  parts  of  the  mucous 
membranes. 

The  basement  membrane  or  membrana  propria  is  best  seen  in  parts 
where  the  mucous  membrane  is  raised  into  villous  processes,  or  where 
it  forms  secreting  crypts  or  minute  glandular  recesses,  such  as  those 
which  abound  in  the  stomach  and  intestinal  canal.  On  tearing  out  a 
portion  of  the  gastric  or  intestinal  mucous  membrane  under  the  micro- 
scope, some  of  the  tubular  glands  are  here  and  there  discovered  which 
are  tolerably  well  cleared  from  the  surrounding  tissue,  and  their  parie- 
tes  are  seen  to  be  formed  of  a thin  pellucid  film,  which  is  detached 
from  the  adjoining  fibro-vascular  layer,  the  epithelium  perhaps  still 
remaining  in  the  inside  of  the  tube  or  having  escaped,  as  the  case  may 
be.  The  fine  film  referred  to  is  the  basement  membrane.  It  may  by 
careful  search  be  seen  too  on  the  part  of  the  corium  situated  between 
the  orifices  of  the  glands,  and  on  the  villi,  when  the  epithelium  is  de- 
tached, although  it  cannot  be  there  separated  from  the  vascular  layer. 
In  these  parts  it  manifestly  forms  a superficial  boundary  to  the  corium, 
passing  continuously  over  its  eminences  and  into  its  recesses,  defining 
its  surface,  and  supporting  the  epithelium.  Where  villi  and  tubular 
glands  are  wanting,  and  where  the  mucous  membrane,  more  simply 
arranged,  presents  an  even  surface,  as  in  the  tympanum  and  nasal 
sinuses,  the  actual  presence  of  a fine  film  or  basement  membrane  can- 
not be  demonstrated.  In  such  situations  it  may  possible  have  originally 
existed  as  a constituent  of  the  corium,  and  have  been  obliterated  or 
rendered  inconspicuous  in  consequence  of  subsequent  modifications. 

The  basement  membrane,  as  already  said,  forms  the  peripheral 
boundary  of  the  corium ; it  is  in  immediate  connexion  with  the  epi- 
thelium, which  it  supports,  and  in  the  production  of  which  it  is  sup- 
posed to  have  probably  some  share.  By  its  under  surface  it  more 
or  less  closely  adjoins  the  fibro-vascular  layer.  The  vessels  of  the 
latter  advance  close  up  to  the  basement  membrane,  but  nowhere 
penetrate  it ; the  delicate  film  of  which  it  consists  is  indeed  wholly 
extra-vascular.  In  respect  of  structure  the  membrane  in  question 
seems  perfectly  homogeneous,  but  marks  resembling  the  nuclei  of 
epithelium  cells  are  sometimes  seen  disposed  evenly  over  its  surface, 
and  some  observers,  considering  these  as  forming  an  integrant  part 
of  the  membrane,  have  looked  on  them  as  so  many  reproductive 
centres  from  which  new  epithelium  particles  are  generated.  Mr. 
Bowman,  on  the  other  hand,  considers  these  objects  as  nuclei  belong- 
ing to  the  undermost,  and  as  it  were  nascent  epithelium  cells,  which 
have  remained  adherent  to  the  really  simple  basement  membrane. 

The  fibro-vascular  layer  of  the  corium  is  composed  of  vessels,  both 
sanguiferous  and  lymphatic,  with  fibres  of  cellular  or  areolar  tissue ; 


MUCOUS  MEMBRANES. 


81 


the  nerves  also  which  belong  to  the  mucous  membrane  are  distributed 
in  this  part  of  its  structure. 

The  vessels  exist  universally  in  mucous  membranes,  except  in  that 
which  covers  the  anterior  surface  of  the  cornea  ; there  the  epithelium 
and  basement  membrane  are  present,  but  no  vessels.  The  branches 
of  the  arteries  and  veins  dividing  in  the  submucous  tissue  send  smaller 
branches  into  the  corium,  which  at  length  form  a network  of  capilla- 
ries in  the  fibro-vascular  layer.  This  capillary  network  lies  imme- 
diately beneath  the  basement  membrane,  advancing  with  that  mem- 
brane into  the  villi  and  papillEe,  to  be  presently  described,  and  sur- 
rounding the  tubes  and  other  glandular  recesses,  into  which  it  is  hol- 
lowed. The  lymphatics  also  form  plexuses,  the  finest  of  which  lie  at 
the  surface,  probably  just  below  the  basement  membrane;  their  ar- 
rangement generally,  as  well  as  in  the  villi,  has  been  already  de- 
scribed. 

The  fibres  of  cellular  tissue  which  enter  into  the  formation  of  the 
corium  are  arranged  in  interlacing  bundles ; but  their  amount  is  very 
different  in  different  parts.  In  some  situations,  as  in  the  gullet,  blad- 
der and  vagina,  the  fibrous  constituent  is  abundant,  and  extends 
throughout  the  whole  thickness  of  the  fibro-vascular  layer,  forming  a 
continuous  and  tolerably  compact  web,  and  rendering  the  mucous 
membrane  of  those  parts  comparatively  stout  and  tough.  In  the 
stomach  and  intestines,  on  the  other  hand,  where  the  membrane  is 
more  complex,  and  at  the  same  time  weaker  in  structure,  the  cellular 
tissue  is  in  small  proportion  ; its  principal  bundles  follow  and  support 
the  blood-vessels,  deserting,  however,  their  finer  and  finest  branches 
which  lie  next  the  basement  membrane  ; and  there  exists,  accordingly, 
next  and  for  a little  depth  below  this  membrane,  a stratum  of  the 
corium,  in  which  very  few  if  any  filaments  of  cellular  tissue  are  seen. 
In  this  superficial  stratum,  the  sanguiferous  capillaries  and  lymphatics 
are  spread  out  amidst  a soft  granular  matter,  with  a few  corpuscles, 
mostly  resembling  cell-nuclei  and  granular  cells.  Here  too,  as  well 
as  deeper  in  the  corium,  a few  bodies  are  seen  having  the  appearance 
of  fusiform  cells.  The  villi  present  the  same  internal  structure  as  this 
superficial  stratum,  and  appear  to  be  prolongations  of  it. 

The  free  surface  of  the  mucous  membranes  is  in  some  parts  plain, 
but  in  others  is  beset  with  little  eminences,  named  papillse  and  villi. 
The  papilloR  are  best  seen  on  the  tongue  ; they  are  small  processes  of 
the  corium,  mostly  of  a conical  and  cylindrical  figure,  containing 
blood-vessels,  and  nerves,  and  covered  with  epithelium.  Some  are 
small  and  simple,  others  larger  and  compound  or  cleft  into  secondary 
papillse.  They  serve  various  purposes ; some  of  them  no  doubt 
minister  to  the  senses  of  taste  and  touch,  many  appear  to  have  chiefly 
a mechanical  office,  while  others  would  seem  intended  to  give  greater 
extension  to  the  surface  of  the  corium  for  the  production  of  a thick 
coating  of  epithelium.  The  villi  are  most  frequently  developed  on  the 
mucous  coat  of  the  small  intestines.  Being  set  close  together  like  the 
pile  or  nap  of  cloth,  they  give  to  the  parts  of  the  membrane  which 
they  cover  the  aspect  usually  denominated  “ villous.”  They  are  in 
reality  little  elevations  or  processes  of  the  superficial  part  of  the 


82 


MUCOUS  MEMBRANES. 


corium,  covered  with  epithelium,  and  containing  blood-vessels  and 
lacteals,  which  are  thus  favourably  disposed  for  absorbing  nutrient 
matters  from  the  intestine.  The  more  detailed  description  of  the 
papilljE  and  villi  belongs  to  the  sp6cial  anatomy  of  the  parts  where 
they  occur. 

In  some  few  portions  of  the  mucous  membrane,  the  surface  is 
marked  with  fine  ridges  which  intersect  each  other  in  a reticular 
manner,  and  thus  inclose  larger  and  smaller  polygonal  pits  or  re- 
cesses. This  peculiar  chnracter  of  the  surface  of  the  membrane, 
which  might  be  called  “ alveolar,”  is  seen  very  distinctly  in  the  gall- 
bladder, and  on  a finer  scale  in  the  vesiculae  seminales ; still  more 
minute  alveolar  recesses  with  intervening  ridges  may  be  discovered 
with  a lens  on  the  mucous  membrane  of  the  stomach. 

Glands  of  mucous  membranes. — Many,  indeed  most  of  the  glands  of 
the  body,  pour  their  secretions  into  the  great  passages  lined  by  mucous 
membranes;  but  while  this  is  true,  there  are  certain  small  glands 
which  may  be  said  to  belong  to  the  membrane  itself,  inasmuch  as  they 
are  found  in  numbers  over  large  tracts  of  that  membrane,  and  yield 
mucus,  or  special  secretions  known  to  be  derived  from  particular  por- 
tions of  the  membrane.  Omitting  local  peculiarities,  the  glands  re- 
ferred to  may  be  described  as  of  three  kinds,  viz.: — 

1.  Tubular  follicles. — These  are  minute  tubes  formed  by  recesses 
or  inversions  of  the  basement  membrane,  and  lined  with  epithelium. 
They  are  usually  placed  perpendicularly  to  the  surface,  and  often 
very  close  together,  and  they  constitute  the  chief  substance  of  the 
mucous  membrane  in  those  parts  where  they  abound,  its  apparent 
thickness  depending  on  the  length  of  the  tubes,  which  differs  conside- 
rably in  different  regions.  The  tubes  open  by  one  end  on  the  surface; 
the  other  end  is  closed,  and  is  either  simple  or  loculated.  The  tubular 
follicles  are  abundant  in  the  stomach,  in  the  small  intestines,  where 
they  are  comparatively  short  and  known  as  the  crypts  of  Lieberkiihn, 
and  in  the  large  intestine.  They  exist  also  in  considerable  numbers  in 
the  mucous  membrane  of  the  uterus. 

2.  Saccular  follicles. — These  are  small  cavities  of  a rounded  shape, 
found  in  various  parts  of  the  mucous  membrane,  but  neither  their 
structure,  nor  the  nature  of  their  secretion,  has  yet  been  sufficiently 
made  out.  Some  of  them  are  habitually  closed,  and  only  open  occa- 
sionally to  give  issue  to  their  secretions  ; others  probably  have  con- 
stantly open  orifices.  Examples  of  the  former  variety  are  found  in 
the  agminated  and  solitary  glands  of  the  intestines. 

3.  Small  compound  glands. — Under  this  head  are  here  compre- 
hended minute  but  still  true  compound  glands  of  the  vesicular  or 
racemose  kind,  with  single  branched  ducts  of  various  lengths,  which 
open  on  different  parts  of  the  membrane.  Numbers  of  these,  yielding 
a mucous  secretion,  open  into  the  mouth  and  windpipe.  They  have 
the  appearance  of  small  solid  bodies,  often  of  a flattened  lenticular 
form,  but  varying  much  both  in  shape  and  size,  and  placed  at  different 
depths  below  the  mucous  membrane  on  which  their  ducts  open.  The 
glands  of  Brunner,  which  form  a dense  layer  in  the  commencing  part 
of  the  duodenum,  are  of  this  kind. 


MUCOUS  MEMBRANES. 


83 


Nerves. — The  mucous  membranes  are  supplied  with  nerves,  and 
endowed  with  sensibility;  but  the  proportion  of  nerves  which  they 
receive,  as  well  as  the  degree  of  sensibility  which  they  possess,  differs 
very  greatly  in  different  parts.  As  to  the  mode  of  distribution  and 
termination  of  their  nerves,  there  is  nothing  to  be  said  beyond  what 
has  been  already  stated  in  treating  of  the  nerves  in  general. 

Secretion. — Mucus  is  a more  or  less  viscid,  transparent,  or  slightly  turbid  fluid, 
of  variable  consistency.  It  is  somewhat  heavier  than  water,  though  expectorated 
mucus  is  generally  prevented  from  sinking  in  that  liquid  by  entangled  air-bub- 
bles. Examined  with  the  microscope,  it  is  found  to  consist  of  a fluid,  containing 
solid  particles  of  Various  kinds,  viz.,  1.  Epithelium  particles  detached  by  desqua- 
mation; 2.  Mucous  corpuscles,  which  are  bodies  resembhng  much  the  pale  cor- 
puscles of  the  blood ; 3.  Nucleated  cells,  with  more  or  less  ample  envelope,  and 
apparently  in  a state  of  transition  from  the  condition  of  mucous  corpuscles  to  that 
of  epithelium  particles.  The  viscidity  of  mucus  depends  on  the  liquid  part,  which 
contains  in  solution  a peculiar  substance,  named  by  the  chemists  mucin.  This 
ingredient  is  precipitated  and  the  mucus  rendered  turbid  by  tlie  addition  of  water 
or  a weak  acid,  but  it  may  be  partly  redissolved  in  an  excess  of  water,  and  com- 
pletely so  in  a strong  acid.  This  mucin  is  soluble  in  alkalies,  and  its  acid  solu- 
tions are  not  precipitated  by  ferrocyanide  of  potassium.  Little  can,  of  course,  be 
expected  from  a chemical  analysis  of  a heterogeneous  and  inseparable  mixture 
of  solid  particles  with  a liquid  solution,  such  as  we  find  in  mucus,  which  is, 
moreover,  subject  to  differences  of  quality  according  to  the  part  of  the  mucous 
membrane  whence  it  is  derived.  Examined  thus  in  the  gross,  however,  the 
nasal  mucus  has  been  found  to  yield  water,  mucin,  alcohol-extract  with  alkaline 
lactates,  water-extract  with  traces  of  albumen  and  a phosphate,  chlorides  of 
sodium  and  potassium,  and  soda.  Fat  has  been  obtained  by  analysis  of  pulmo- 
nary mucus,  reputed  healthy. 

Regeneration. — The  reparatory  process  is  active  in  the  mucous  membranes. 
Breaches  of  continuity  occasioned  by  sloughing,  ulceration,  or  other  causes,  rea- 
dily heal.  The  steps  of  the  process  have  been  examined  with  most  care  in  the 
healing  of  ulcers  of  the  large  intestine,  and  in  such  cases  it  has  been  found  that 
the  resulting  cicatrix  becomes  covered  with  epithelimn,  but  that  the  tubular 
follicles  are  not  reproduced. 


THE  SKIN. 


The  skin  consists  of  the  cutis  vera  or  corium  and  the  cuticle  or 
epidermis. 

The  epidermis,  cuticle,  or  scarf  skin,  belongs  to  the  class  of  epithelial 
structures,  the  general  nature  of  which  has  been  already  considered. 
It  forms  a protective  covering  over  every  part  of  the  true  skin,  and  is 
itself  quite  insensible  and  non-vascular.  The  thickness  of  the  cuticle 
varies  in  diflerent  parts  of  the  surface,  measuring  in  some  not  more 
than  ^lo^h,  and  in  others  from  2’^th  to  y^th  of  an  inch.  It  is  thickest 
in  the  palms  of  the  hands  and  soles  of  the  feet,  where  the  skin  is  much 
exposed  to  pressure,  and  it  is  not  improbable  that  this  may  serve  to 
stimulate  the  subjacent  true  skin  to  a more  active  formation  of  epi- 
dermis; but  the  difference  does  not  depend  solely  on  external  causes, 
for  it  is  well  marked  even  in  the  foetus. 

Structure. — The  cuticle  is  made  up  of  flattened  cells  agglutinated 
together  in  many  irregular  layers.  These  cells  arise  in  a blastema, 


[Fig.  286. 


Under  surface  of  the  cuticle,  detached  by  maceration  from  the  palm;  showing  the  double 
rows  of  depressions  in  which  the  papillae  have  been  lodged,  with  the  hard  epithelium  lining  the 
sudoriferous  ducts  in  their  course  through  the  cutis.  Some  of  these  are  contorted  at  the  end, 
where  they  have  entered  the  sweat-gland. — Magnified  30  diameters. — Todd  and  Bowman.] 

which  is  poured  out  on  the  surface  of  the  true  skin.  They  are  at  first 
round,  and  contain  nuclei  with  soft  and  moist  contents,  but,  by  suc- 
cessive formations  beneath  them,  they  are  gradually  pushed  to  the  free 


THE  SKIN. 


85 


surface,  and  in  their  progress  become  flattened  into  thin  irregular 
scales,  for  the  most  part  lose  their  nuclei,  and  are  at  last  thrown  off 
by  desquamation.  As  the  cells  change  their  form,  they  undergo 
chemical  and  physical  changes  in  the  nature  of  their  contents ; for 
those  in  the  deeper  layers  contain  a soft,  opaque,  granular  matter, 
soluble  as  well  as  their  envelope  in  acetic  acid,  whilst  the  superficial 
ones  are  transparent,  dry,  and  firm,  and  are  not  affected  by  that  acid. 
It  would  seem  as  if  their  contents  were  converted  into  a horny  matter, 
and  that  a portion  of  this  substance  is  employed  to  cement  them 
together.  The  more  firm  and  transparent  superficial  part  of  the  epi- 
dermis may  be  separated  from  the  deeper,  softer,  more  opaque,  and 
recently  formed  part,  which  constitutes  what  is  called  the  rete 
mucosum. 

Many  of  the  cells  of  the  cuticle  contain  pigment,  and  often  give  the 
membrane  more  or  less  of  a tawny  colour,  even  in  the  white  races  of 
mankind ; the  blackness  of  the  skin  in  the  negro  depends  entirely  on 
the  cuticle.  The  pigment  is  contained  principally  in  the  cells  of  the 
deep  layer  or  rete  mucosum,  and  appears  to  fade  as  they  approach  the 
surface,  but  even  the  superficial  part  possesses  a certain  degree  of 
colour.  More  special  details  respecting  the  pigment  have  been  already 
given  (page  69). 

The  under  or  attached  surface  [fig.  286]  of  the  cuticle  is  moulded 
on  the  adjoining  surface  of  the  corium,  and,  when  separated  by 
maceration  or  putrefaction,  presents  impressions  corresponding  exactly 
with  the  papillary  or  other  eminences,  and  the  furrows  or  depressions 
of  the  true  skin ; the  more  prominent  inequalities  of  the  latter  are 
marked  also  on  the  outer  surface  of  the  cuticle,  but  less  accurately. 
Fine  tubular  prolongations  of  the  cuticle  sink  down  into  the  ducts  of 
the  sweat  glands,  and  are  often  partially  drawn  out  from  their  recesses 
when  the  cuticle  is  detached,  appearing  then  like  threads  proceeding 
from  its  under  surface. 

Chemical  composition. — ^The  cuticle  consists  principally  of  a substance  peculiar 
to  the  epithelial  and  horny  tissues,  and  named  keratin.  This  horny  matter  is  in- 
soluble in  water  at  ordinary  temperatures,  and  insoluble  in  alcohol.  It  is  soluble 
in  the  caustic  alkalies.  In  composition,  it  is  analogous  to  the  albuminoid  princi- 
ples, but  with  a somewhat  larger  proportion  of  oxygen;  like  these,  it  contains 
sulphur.  Besides  keratin,  the  epidermis  yields,  on  analysis,  a small  amount  of 
fat,  with  salts,  and  traces  of  the  oxides  of  iron  and  manganese.  The  tissue  of 
the  cuticle  readily  imbibes  water,  by  which  it  is  rendered  soft,  thick,  and  opaque, 
but  it  speedily  dries  again,  and  recovers  its  usual  characters. 

The  true  skin,  cutis  vera,  derma,  or  corium,  is  a sentient  and  vas- 
cular texture.  It  is  covered  and  defended,  as  already  explained,  by 
the  insensible  and  non-vascular  cuticle,  and  is  attached  to  the  parts 
beneath  by  a layer  of  cellular  tissue,  named  “ subcutaneous,”  which, 
excepting  in  a few  parts,  contains  fat,  and  has  therefore  been  called 
also  the  “ panniculus  adiposus.”  The  connexion  is  in  many  parts  loose 
and  movable,  in  others  close  and  firm,  as  in  the  palmar  surface  of  the 
hand  and  the  sole  of  the  foot,  where  the  skin  is  fixed  to  the  subjacent 
fascia  by  numerous  stout  fibrous  bands,  the  space  between  being  filled 
with  a firm  padding  of  fat.  In  some  regions  of  the  body  the  skin  is 
moved  by  muscular  fibres,  which,  as  in  the  case  of  the  orbicular  mus- 

VOL.  II.  8 


86 


THE  SKIN. 


cle  of  the  mouth,  may  be  unconnected  to  fixed  parts,  or  may  be  at- 
tached beneatli  to  bones  or  fascia3,  like  the  other  cutaneous  muscles  of 
the  face  and  neck,  and  the  short  palmar  muscle  of  the  hand. 

Structure. — The  corium  consists  of  a fibro-vascular  layer,  which  is 
supposed  to  be  bounded  at  the  surface  next  the  cuticle  by  a fine  homo- 
geneous basement  membrane  or  memhrana propria,  like  the  correspond- 
ing part  of  the  mucous  membrane.  No  such  superficial  film  can,  it  is 
true,  be  raised  from  the  corium,  but  from  its  distinct  presence  in  small 
gland-ducts  which  are  continuous  with  the  corium,  and  from  the 
well-defined  outline  presented  by  the  papillary  eminences  on  its  sur- 
face, it  is  presumed  that  a limitary  membrane  of  this  sort  ought  to  be 
reckoned  as  an  element  of  the  corium,  although,  as  in  the  analogous 
case  of  the  mucous  membrane,  it  cannot  be  shown  to  exist  over  the 
whole  surface.  fibro-vaseular  part  is  made  up  of  an  exceedingly 
strong  and  tough  framework  of  interlaced  fibres,  with  blood-vessels 
and  lymphatics.  The  fibres  are  chiefly  of  the  white  variety,  such  as 
constitute  the  chief  part  of  the  fibrous  and  areolar  tissues,  and  are 
arranged  in  stout  interlacing  bundles,  except  at  and  near  the  surface, 
where  the  texture  of  the  corium  becomes  very  fine.  With  these  are 
mixed  yellow  or  elastic  fibres,  which  vary  in  amount  in  dilTerent  parts, 
but  in  all  cases  are  present  in  much  smaller  proportion  than  the  former 
kind.  The  interlacement  becomes  much  closer  and  finer  towards  the 
free  surface  of  the  corium,  and  there  the  fibres  can  be  discovered  only 
by  teasing  out  the  tissue.  Towards  the  attached  surface,  on  the  other 
hand,  the  texture  becomes  much  more  open,  with  larger  and  larger 
meshes,  in  which  clumps  of  fat  and  the  small  sudatory  glands  are 
lodged,  and  thus  the  fibrous  part  of  the  skin  becoming  more  and  more 
lax  and  more  mixed  with  fat,  blends  gradually  with  the  subcutaneous 
areolar  tissue  to  which  it  is  allied  in  elementary  constitution. 

In  consequence  of  this  gradual  transition  of  the  corium  into  the  sub- 
jacent tissue,  its  thickness  cannot  be  assigned  with  perfect  precision. 
It  is  generally  said  to  measure  from  a quarter  of  a line  or  less  to  nearly 
a line  and  a half.  As  a general  rule,  it  is  thicker  on  the  posterior  aspect 
of  the  head,  neck,  and  trunk,  than  in  front;  and  thicker  on  the  outer 
than  on  the  inner  side  of  the  limbs.  The  corium,  as  well  as  the 
cuticle,  is  remarkably  thick  on  the  soles  of  the  feet  and  palms  of  the 
hands.  The  skin  of  the  female  is  thinner  than  that  of  the  male. 

The  free  surface  of  the  corium  is  marked  in  various  places  with 
larger  or  smaller  furrows,  which  also  affect  the  superjacent  cuticle. 
The  larger  of  them  are  seen  opposite  the  flexures  of  the  joints,  as  those 
so  well  known  in  the  palm  of  the  hand  and  at  the  joints  of  the  fingers. 
The  finer  furrows  intersect  each  other  at  various  angles,  and  may  be 
seen  almost  all  over  the  surface : they  are  very  conspicuous  on  the 
back  of  the  hands.  These  furrows  are  not  merely  the  consequence  of 
the  frequent  folding  of  the  skin  by  the  action  of  muscles  or  the  bending 
of  the  joints,  for  they  exist  in  the  foetus.  The  wrinkles  of  old  persons 
are  of  a different  nature,  and  are  caused  by  the  wasting  of  the  soft 
parts  which  the  skin  covers.  Fine  curvilinear  ridges,  with  intervening 
furrows,  mark  the  skin  of  the  palm  and  sole;  these  are  caused  by 
ranges  of  the  papillae,  to  be  immediately  described. 


THE  SKIN. 


87 


Papilla. — The  free  surface  of  the  corium  is  beset  with  small  emi- 
nences thus  named,  which  seem  chiefly  intended  to  contribute  to  the 
perfection  of  the  skin  as  an  organ  of  touch,  seeing  that  they  are  highly 
developed  where  the  sense  of  touch  is  exquisite,  and  vice  versa.  They 
serve  also  to  extend  the  surface  for  the  production  of  the  cuticular 
tissue,  and  hence  are  large-sized  and  numerous  under  the  nail.  The 
papillae  are  large  and  in  close  array  on  the  palm  and  palmar  surface 
of  the  fingers,  and  on  the  corresponding  parts  of  the  foot  (fig.  287). 
There  they  are  ranged  in  lines,  forming  the  curvilinear  ridges  seen 
when  the  skin  is  still  covered  with  its  thick  epidermis.  They  are  of 

[Fig.  287.  Fig.  288. 


Fig.  287.  Papillae  of  the  palm,  the 
cuticle  being  detached.  Magnified  35 
diameters. — Todd  and  Bowman. 

Fig.  288.  Surface  of  the  skin  of  the 
palm,  showing  the  ridges,  furrows,  cross 
grooves,  and  orifices  of  the  sweat-ducts. 

The  scaly  texture  of  the  cuticle  is  indi- 
cated by  the  irregular  lines  on  the  sur- 
face. Magnified  20  diam. — Todd  and 
Bowman.] 

a conical  figure,  rounded  or  blunt  at  the  top,  and  are  received  into 
corresponding  pits  on  the  under  surface  of  the  cuticle.  They  measure 
on  the  hand  from  to  of  an  inch  in  height.  In  the  ridges, 

the  large  papillre  are  placed  sometimes  in  single  but  more  commonly 
in  double  rows,  with  smaller  ones  between  them,  that  is,  also  on  the 
ridges,  for  there  are  none  in  the  intervening  grooves.  These  ridges 
are  marked  at  short  and  tolerably  regular  intervals  with  notches,  or 
short  transverse  furrows,  in  each  of  which,  about  its  middle,  is  the 
minute  funnel-shaped  orifice  of  the  duct  of  a sweat-gland  (fig.  288). 
Fine  blood-vessels  enter  the  papillae,  forming  either  simple  capillary 
loops  in  each,  or  dividing  into  two  or  more  capillary  branches,  ac- 
cording to  the  size  of  the  papilla,  which  turn  round  in  form  of  loops 
and  return  to  the  veins.  Filaments  of  nerves  are  also  to  be  discovered 
ascending  into  the  papillae,  but  their  mode  of  termination  is  doubtful, 
and  what  is  known  on  the  subject  will  be  stated  hereafter.  In 
other  parts  of  the  skin  endow’ed  with  less  sensibility,  the  papillae 
are  smaller,  shorter,  fewer  in  number,  and  irregularly  scattered.  In 
parts  where  they  are  naturally  small,  they  often  become  enlarged  by 
chronic  inflammation  round  the  margin  of  sores  and  ulcers  of  long 
standing,  and  are  then  much  more  conspicuous. 

Blood-vessels  and  lymphatics.  — The  blood-vessels  divide  into 
branches  in  the  subcutaneous  tissue,  and,  as  they  enter  the  skin,  sup- 
ply capillary  plexuses  to  the  fat  clumps,  sweat  glands,  and  hair  fol- 


88 


NAILS. 


licles.  They  divide  and  anastomose  still  further  as  they  approach  the 
surface,  and  at  length  on  reaching  it,  form  a dense  network  of  capil- 
laries, with  rounded  polygonal  meshes,  as  previously  represented  in 
figure  232.  Fine  branches  are  sent  into  the  papillae,  as  already  men- 
tioned. The  lymphatics  are  abundant  in  some  parts  of  the  skin,  as  on 
the  scrotum  and  round  the  nipple ; whether  they  are  equally  so  in  all 
parts  may  be  doubted.  They  form  networks,  which  become  finer  as 
they  approach  the  surface,  and  communicate  underneath  with  straight 
vessels,  and  these,  after  a longer  or  a shorter  course,  join  larger  ones, 
or  enter  lymphatic  glands. 

JVerves. — Nerves  are  supplied  in  very  different  proportions  to  differ- 
ent regions  of  the  skin,  and  according  to  the  degree  of  sensibility. 
Their  mode  of  termination  has  been  already  considered. 

Chemical  composition. — The  corium  being  composed  chiefly  of  white  fibrous 
tissue,  has  a corresponding  chemical  composition.  It  is,  accordingly,  in  a great 
measure,  resolved  into  gelatin  by  boiling,  and  hence,  also,  its  conversion  into 
leather  by  the  tanning  process. 

JVails  and  Hairs. — The  nails  and  hairs  are  growths  of  the  epider- 
mis, agreeing  essentially  in  nature  with  that  membrane  ; like  the  epi- 
dermis, they  are  destitute  of  vessels  and  nerves  and  separable  from  the 
cutis. 

Nails. — The  posterior  part  of  the  nail  [fig.  289],  which  is  concealed  in  a 

groove  of  the  skin,  is  named  its  “ root,” 
the  uncovered  part  is  the  “ body,” 
which  terminates  in  front  by  the  “ free 
edge.”  A small  portion  of  the  nail 
near  the  root,  named  from  its  shape 
the  lunula,  is  whiter  than  the  rest. 
This  appearance  is  due  partly  to  some 
degree  of  opacity  of  the  substance  of 
the  nail  at  this  point  and  partly  to  the 
skin  beneath  being  less  vascular  than 
in  front. 

The  part  of  the  corium  to  which  the 

Section  of  the  skin  on  the  end  of  the  jg  attached,  and  by  which  in  fact 

finger: — The  cuticle  and  nail,  n,  detached  . . ’ J . 

from  the  cutis  and  matrix,  m.— Todd  and  it  IS  Secreted  or  generated,  IS  named 
Bowman]  the  matrix  [fig.  289,  ?w].  This  portion 

of  the  skin  is  highly  vascular  and  thickly  covered  with  large  vascular 
papillae.  Posteriorly  the  matrix  is  bounded  by  a crescentic  groove  or 
fold,  deep  in  the  middle  but  getting  shallower  at  the  sides,  which 
lodges  the  root  of  the  nail.  The  small  lighter  coloured  part  of  the 
matrix  next  the  groove  and  corresponding  with  the  lunula  of  the  nail, 
is  covered  with  papillae  having  no  regular  arrangement,  but  the  whole 
remaining  surface  of  the  matrix  situated  in  front  of  this,  and  support- 
ing the  body  of  the  nail,  is  marked  with  longitudinal  and  very  slightly 
diverging  ridges  formed  by  rows  of  papillm.  The  cuticle,  advancing 
from  the  back  of  the  finger,  becomes  attached  to  the  upper  surface  of 
the  nail  near  its  posterior  edge,  that  is,  all  round  the  margin  of  the 
groove  in  which  the  nail  is  lodged ; in  front  the  cuticle  of  the  point  of 
the  finger  becomes  continuous  with  the  under  surface  of  the  nail  a 
little  way  behind  its  free  edge. 


[Fig.  289. 
^ fi 


HAIRS. 


89 


The  substance  of  the  nail,  like  that  of  the  cuticle,  is  naade  up  of 
scales  derived  from  flattened  cells.  The  oldest  and  most  superflcial 
of  these  are  the  broadest  and  hardest,  but  at  the  same  time  very  thin 
and  irregular,  and  so  intimately  and  confusedly  connected  together 
that  their  respective  limits  are  scarcely  discernible.  But  the  youngest 
cells,  which  are  those  situated  at  the  root  and  under  surface,  are 
softer,  and  of  a rounded  or  polygonal  shape,  and  still  retain  their 
nuclei.  In  chemical  composition  the  nails  resemble  epidermis. 

The  growth  of  the  nail  is  effected  by  a constant  generation  of  cells 
at  the  root  and  under  surface.  Each  successive  sCTies  of  these  cells 
being  followed  and  pushed  from  their  original  place  by  others,  lose 
their  nuclei,  and  become  flattened  into  dry,  hard,  and  inseparably 
coherent  scales.  By  the  addition  of  new  cells  at  the  posterior  edge 
the  nail  is  made  to  advance,  and  by  the  apposition  of  similar  particles 
to  its  under  surface  it  is  maintained  of  due  thickness.  The  nail  being 
thus  merely  an  exuberant  part  of  the  epidermis,  the  question  whether 
that  membrane  is  continued  underneath  it  loses  its  significance.  When 
a nail  is  thrown  off  by  suppuration  or  pulled  away  by  violence,  a new 
one  is  produced  in  its  place,  provided  the  matrix  remains. 

Hairs. — A hair  consists  of  the 


root,  which  is  fixed  in  the  skin, 
the  shaft  or  stem,  and  the  point. 
The  stem  is  generally  cylindrical, 
but  often  more  or  less  flattened, 
sometimes  it  is  grooved  along  one 
side,  and  therefore  reniform  in  a 
cross  section  ; when  the  hair  is  en- 
tire it  becomes  gradually  smaller 
towards  the  point.  The  length 
and  thickness  vary  greatly  in  dif- 
ferent individuals  and  races  of 
mankind  as  well  as  in  different 
regions  of  the  body.  Light  colour- 
ed hair  is  usually  finer  than  black. 

The  stem  is  covered  with  a coat- 
ing of  finely  imbricated  scales,  the 
projecting  serrated  edges  of  which 
give  rise  to  a series  of  fine  waved 
transverse  lines,  which  may  be 
seen  with  the  microscope  on  the 
surface  of  the  hair.  VVithin  this 
scaly  covering  is  a fibrous  sub- 
stance, which  in  all  cases  consti- 
tutes the  chief  part  and  often  the 
whole  of  the  stem ; but  in  many 
hairs  the  axis  is  occupied  by  a sub- 
stance of  a different  nature,  called 


[Fig.  290. 


a.  Transverse  section  of  a hair  of  the  head, 
showing  the  exterior  cortex,  the  med  ulla  or  pith 
with  its  scattered  pigment,  and  a central  space 
filled  with  pigment,  b.  A similar  section  of  a 
hair,  at  a point  where  no  aggregation  of  pig- 
ment in  the  axis  exists,  c.  Longitudinal  sec- 
tion, without  a central  cavity,  showing  the  im- 
brication ot  the  cortex,  and  the  arrangement 
of  the  pigment  in  the  fibrous  part.  d.  Surface, 
showing  the  sinuous  transverse  lines  formed 
by  the  edges  of  the  cortical  scales,  d'.  A por- 
tion of  the  margin,  showing  their  imbrication. 
Magn.  150  diara. — Todd  and  Bowman  ] 


the  medulla  or  pith,  [fig.  290,]  for 
which  reason  the  surrounding  fibrous  part  is  often  named  “ cortical,” 
although  this  term  is  more  properly  applied  to  the  superficial  coating 

8* 


90 


HAIRS. 


of  scales  abovementioned.  The  fibrous  substance  is  translucent,  with 
short  longitudinal  opaque  streaks  of  darker  colour  intermixed ; it  is 
made  up  of  straight,  rigid,  longitudinal  fibres,  which,  when  separated, 
are  found  to  be  flattened,  broad  in  the  middle,  and  pointed  at  each 
end,  wdih  dark  and  rough  edges.* 

These  fibres,  as  will  be  afterwards  explained,  are  derived  from 
elongated  and  metamorphosed  cells ; they  are  mostly  transparent  or 
marked  with  only  a few  dark  specks.  The  coloured  streaks  in  the 
fibrous  substance  are  caused  by  collections  of  pigment  or  elongated 
cell-nuclei. 

The  medulla,  or  pith,  as  already  remarked,  does  not  exist  in  all 
hairs.  It  is  wanting  in  the  fine  hairs  over  the  general  surface  of  the 
body,  and  is  not  commonly  met  with  in  those  of  the  head.  When 
present  it  occupies  the  centre  of  the  shaft  and  ceases  towards  the 
point.  It  is  more  opaque  and  deeper  coloured  than  the  fibrous  part; 
in  the  white  hairs  of  quadrupeds  it  is  opaque  and  white.  It  seems  to 
be  composed  of  little  clumps  or  clusters  of  minute  particles,  some  re- 
sembling pigment  granules,  others  like  very  fine  fat  granules,  which 
form  a continuous  dark  mass  along  the  middle  of  the  stem,  or  are  in- 
terrupted at  parts  for  a greater  or  less  extent.  In  the  latter  case,  the 
axis  of  the  stem  at  the  interruptions  may  be  fibrous  like  the  surround- 
ing parts,  or  these  intervals  may  be  occupied  by  a clear,  colourless 
matter ; and,  according  to  Henle,  some  hairs  present  the  appearance 


Fig.  291. 


of  a sort  of  canal  running  along 
the  axis,  and  filled  in  certain 
parts  with  opaque  granular  mat- 
ter, and  in  others  with  a homo- 
geneous transparent  substance. 

The  rooi  of  the  hair  is  lighter  in 
colour  and  softer  than  the  stem ; it 
swells  out  at  its  lower  end  into  a 
bulbous  enlargement  or  knob,  and 
is  received  into  a recess  of  the 
skin  named  the  hair  follicle, 
which,  when  the  hair  is  of  consi- 
derable size,  reaches  down  into 
thesubcutaneousfat.  The  follicle, 
which  receives  near  its  mouth  the 
opening  ducts  of  one  or  more  se- 
baceous glands,  is  somewhat 
dilated  at  the  bottom,  to  corre- 
spond with  the 


Magnified  view  of  the  root  of  the  hair  (after  lOOt  ; it  Consists  of  an  Outer  COat, 
Kohlriiusch).  a.  Stem  or  shaft  of  hair  cut  across,  continuous  with  the  COfium  (fig. 

h.  Inner,  and  c outer  layer  of  the  epidermic  lining  , 7.  . 

the  hair  follicle,  called  also  the  root-sheath,  d.  291,  d,  d),  and  an  epidei  mic 
Dermic  or  external  coat  of  the  hair  follicle,  shown  hninS’  (b,  c),  COntinUOUS  with  the 

cuticle,  ihe  outer  or  dermic 
coat  is  thin,  but  firm ; it  is  made 


bulging  of  the 


lining 

of  the  hair  follicle,  called  also  the  root-sheath. 

'wn  linil.5 

in  part.  c.  Imbricated  scales  about  to  form  a cor-  - ■ 
tical  layer  on  the  surface  of  the  hair. 


* The  breadth  of  these  fibres,  measured  at  the  middle,  is  stated  by  Henle  at  ^p_jth  of  an 
inch,  but  Bidder  affirms  that,  on  macerating  a hair  in  hydrochloric  acid,  it  may  be  split 
into  fibres  a great  deal  smaller  than  this. 


HAIRS. 


91 


up  of  fibres  like  those  of  the  corium,  and  is  well  supplied  with  blood- 
vessels. The  epidermic  lining  adheres  closely  to  the  root  of  the  hair, 
and  commonly  separates,  in  great  part,  from  the  follicle,  and  abides  by 
the  hair,  when  the  latter  is  pulled  out ; hence  it  is  sometimes  named 
the  “ root-sheath.”  It  consists  of  an  outer,  softer,  and  more  opaque 
stratum  (fig.  291,  c,  c)  next  the  dermic  coat  of  the  follicle,  and  an  in- 
ternal more  transparent  layer  {b,  b)  next  the  hair.  The  former  cor- 
responds with  the  deeper  and  more  recent  layer  of  the  cuticle  in 
general,  and  contains  blastema,  with  nuclei,  and  growing  cells ; the 
latter  represents  the  superficial  and  more  mature  part  of  the  cuticle, 
and  consists  of  oblong  flattened  cells,  many  of  them  with  nuclei,  and 
lying  two  or  three  deep.  This  innermost  layer,  when  detached,  exhi- 
bits impressions  of  cross  lines  on  its  surface,  corresponding  with  those 
of  the  imbricated  scaly  coating  of  the  hair,  next  which  it  lies.  Be- 
tween the  two  layers  of  the  cuticular  lining  here  described  is  inter- 
posed a lamina  of  fenestrated  membrane,  transparent  and  homogene- 
ous, and  perforated  with  round,  oval,  and  irregular-shaped  holes.* 

The  soft  bulbous  enlargement  of  the  root  of  the  hair  is  attached  by 
its  base  to  the  bottom  of  the  follicle,  and  at  the  circumference  of  this 
attached  part  it  is  continuous  with  the  epidermic  lining  ; at  the  bottom 
of  the  follicle  it,  in  fact,  takes  the  place  of  the  epidermis,  of  which  it 
is  a growth  or  extension,  and  this  part  of  the  follicle  is  the  true  matrix 
of  the  hair,  being,  in  reality,  a part  of  the  corium  (though  sunk  below 
the  general  surface),  which  supplies  material  for  the  production  of  the 
hair.  This  productive  part  of  the  follicle  is,  accordingly,  remarkably 
vascular,  and,  in  the  large  tactile  hairs  on  the  snout  of  the  seal,  is 
raised  in  form  of  a conical  papilla  or  pulp,  which  fits  into  a corre- 
sponding excavation  of  the  hair  root,  but  there  is  no  such  marked  ele- 
vation in  the  bottom  of  the  human  hair  follicle.  Nervous  branches  of 
considerable  size  enter  the  follicles  of  the  large  tactile  hairs  referred 
to,  and  are  probably  distributed  to  the  papillae,  though,  of  course,  not 
to  the  substance  of  the  hair;  the  pain  occasioned  by  pulling  the  hair 
would  seem  to  suggest  that  the  human  hair  follicles  are  not  unprovided 
with  nerves. 

Growth  of  hair. — On  the  surface  of  the  vascular  matrix,  at  the  bot- 
tom of  the  follicle,  blastema  is  thrown  out,  in  which  nucleated  cells 
arise.  The  cells,  many  of  which  previously  get  filled  with  pigment, 
for  the  most  part  lengthen  out  into  the  flattened  fibres  and  coloured 
streaks  which  compose  the  fibrous  part  of  the  hair;  their  nuclei,  at 
first,  also  lengthen  in  the  same  manner,  but,  at  last,  mostly  become 
indistinct.  The  cells  next  the  circumference  expand  into  the  scales 
which  form  the  imbricated  cortical  layer  (fig.  291,  e,  e).  The  medulla, 
where  it  exists,  is  formed  by  the  cells  nearest  the  centre;  these  retain 

* The  fenestrated  membrane  was  first  pointed  out  in  the  hair-sheath  by  Henle,  who  de- 
scribed it  as  lying  next  to  the  hair  ; but  Mr.  Huxley  has  shown  that  a stratum  of  nucleated 
cells  intervenes  between  it  and  the  surface  of  the  hair.  (Med.  Gaz.  Nov.  1845,  p.  1340.) 
Kohlrausch  conceived  that  the  appearance  of  a fenestrated  membrane  was  fallacious,  and 
was  occasioned  by  laceration  of  the  inner  transparent  layer  of  oblong  cells.  This  inner 
layer  may,  it  is  true,  be  readily  lacerated,  but  I have  nevertheless  satisfied  myself  of  the 
independent  existence  of  a fenestrated  membrane,  interposed,  as  Mr.  Huxley  describes,  be- 
tween the  outer  and  inner  layers  of  the  cuticular  lining  of  the  hair-follicle, — however  difli- 
cult  it  may  be  to  reconcile  this  fact  with  the  known  constitution  of  the  cuticle  in  general. 


92 


HAIRS. 


their  primitive  figure  longer  than  the  rest;  their  cavities  coalesce  to- 
gether by  destruction  of  their  mutually  adherent  parietes,  whilst  col- 
lections of  pigment  granules  make  their  appearance  in  them  and 
around  their  nuclei,  forming  an  opaque  mass,  which  occupies  the  axis 
of  the  hair. 

The  substance  of  the  hair,  like  that  of  the  cuticle,  is  quite  extravas- 
cular,  but,  like  that  structure  also,  it  is  organized  and  subject  to  inter- 
nal organic  changes.  Thus,  in  the  progress  of  its  growth,  the  cells 
change  their  figure,  and  acquire  greater  consistency.  In  consequence 
of  their  elongation,  the  hair,  bulbous  at  the  commencement,  becomes 
reduced  in  diameter  and  cylindrical  above.  But  it  cannot  be  said  to 
what  precise  distance  from  the  root  organic  changes  may  extend.  Some 
have  imagined  that  the  hairs  are  slowly  permeated  by  a fluid,  from 
the  root  to  the  point,  but  this  has  not  been  proved.  The  sudden  change 
of  the  colour  of  the  hair  from  dark  to  gray,  which  sometimes  happens, 
has  never  been  satisfactorily  explained. 

Development  of  the  hair  inthe  foetus. — According  to  Valentin,  the  mdiments  of  the 
hairs  appear  at  the  end  of  the  third  or  beginning  of  the  fourth  month  of  intra-ute- 
rine  life,  as  little  black  specks  beneath  the  cuticle.  From  the  investigations  of 
Gustar-us  Simon,  on  the  origin  of  the  hairs  in  the  fetal  pig,  it  would  seem  that 
the  follicle  is  the  first  part  to  appear.  This  is  formed  of  a saccular  or  cylindrical 
recess  of  the  skin,  lined  with  epidermis,  but  whether  it  be  at  first  also  closed  by 
that  membrane  is  uncertain.  Most  of  these  follicles  contahi  dark-coloured  pig- 
ment cells  on  their  parietes,  and  a larger  collection  of  them  at  the  bottom,  which 
corresponds  to  the  knob  or  bulbous  part  of  the  future  hair;  but  in  some  this  part 
consists  of  colourless  cells.  The  diminutive  hair  then  appears,  its  shaft  being 
disproportionately  small.  As  it  lengthens  it  becomes  bent  on  itself  like  a whip, 
and  the  doubled  part  first  protrudes  from  the  follicle.  The  first  hairs  produced  in 
the  human  fetus  constitute  the  lanugo ; their  eruption  takes  place  about  the  fifth 
month,  but  many  of  them  are  shed  before  birth,  and  are  found  floating  in  the 
liquor  amnii. 

Rep-oduction. — When  a hair  is  pulled  out  a new  one  grows  in  its  place,  provided 
the  follicle  remains  entire.  The  steps  of  this  process  have  been  experimentally 
studied  by  Heusinger,  on  the  large  hairs  situated  on  the  lips  of  the  dog.  He  found 
that  a new  hair  appeared  above  the  surface  in  a few  days  after  the  evulsion  of 
the  old  one,  and  attained  its  full  size-  in  about  three  weeks.  Blood  was  at  first 
effused  into  the  follicle,  but  was  subsequently  absorbed,  and  after  some  inflam- 
mation and  swelling  of  the  coats  of  the  follicle,  which  soon  subsided,  the  new 
hair  commenced  as  a black  spot  on  the  pulp  at  the  bottom;  it  then  lengthened 
out  and  appeared  above  the  surface.  When  quadrupeds  shed  and  renew  their 
hair,  the  new  hair  is  produced  in  the  old  follicle. 

Dwtribution  and  arrangement. — Hairs  are  found  on  all  parts  of  the  skin  except 
the  palms  of  the  hands  and  soles  of  the  feet,  the  dorsal  surface  of  the  third  pha- 
langes of  the  fingers  and  toes,  the  upper  eyelids,  the  glans,  and  the  inner  surface 
of  the  prepuce.  They  are  for  the  most  part  grouped  together,  and  not  placed  at 
equal  distances.  Except  those  of  the  eyelashes,  which  are  implanted  perpendi- 
cularly to  the  surface,  they  have  usually  a slanting  direction,  which  is  wonderfully 
constant  in  the  same  parts.* 

Chemical  nature. — The  chemical  composition  of  hair  has  been  investigated 
principally  by  Vauquelin,  Scherer,  and  Van  Laer.  When  treated  with  boiling 
alcohol,  and  with  ether,  it  yields  a certain  amount  of  oily  fat,  consisting  of  mar- 
garin,  margaric  acid,  and  olein,  which  is  red  or  dark-coloured,  according  to  the 
tint  of  the  hair.  The  animal  matter  of  the  hair  thus  freed  from  fat,  is  supposed 

• The  direction  of  the  hairs  in  different  parts,  is  well  seen  in  the  new-born  infant.  As 
so  observed,  it  has  been  described  and  represented  in  figures,  by  Eschericht.  Muller’s  Ar- 
chiv.,  1837. 


HAIRS. 


93 


to  consist  of  a substance  yielding  gelatin,  and  a protein  compound  containing  a 
large  proportion  of  sulphur.  It  is  insoluble  in  water,  unless  by  long  boiling  under 
pressure,  by  which  it  is  reduced  into  a viscid  mass.  It  readily  and  completely 
dissolves  in  caustic  alkalies.  By  calcination  hair  yields  from  1 to  li  per  cent  of 
ashes,  which  consist  of  the  following  ingredients,  viz.,  peroxide  of  iron,  and  ac- 
cording to  Vauquelin,  traces  of  manganese,  silica,  chlorides  of  sodium  and  potas- 
sium, sulphates  of  lime  and  magnesia,  and  phosphate  of  lime.  With  the  exception 
of  the  bones  and  teeth,  no  tissue  of  the  body  withstands  decay  after  death  so  long 
as  the  hair,  and  hence  it  is  often  found  preserved  in  sepulchres,  when  nothing 
else  remains  but  the  skeleton. 

Glands  of  the  skin. — These  are  of  two  kinds,  the  sebaceous,  which 
yield  a fatty  secretion,  and  the  sweat  glands. 

The  sebaceous  glands  [fig.  292,]  pour  out  their  secretion  at  the  roots 
of  the  hairs,  for,  with  a very  few  isolated  exceptions,  they  open  into 


[Fig.  292. 


Sebaceous  glands,  showing  their  size  and  relation  to  the  hair  follicles; — a and  b from  the 
nose;  c from  the  beard.  In  the  latter  the  cutis  sends  down  an  investment  of  the  hair  follicle. — 
Magnified  18  diameters. — Todd  and  Bowman.] 

the  hair  follicles,  and  are  found  wherever  there  are  hairs.  Each  has  a 
small  duct,  which  opens  at  a short  distance  within  the  mouth  of  the 
hair  follicle,  and,  by  its  other  end,  leads  to  a cluster  of  small  rounded 
secreting  saccules,  which,  as  well  as  the  duct,  are  lined  by  epithelium, 
and  usually  charged  with  the  fatty  secretion,  mixed  with  detached  epi- 
thelium particles.  The  number  of  saccular  recesses  connected  with 
the  duct  usually  varies  from  four  or  five  to  twenty ; it  may  be  reduced 
to  two  or  three,  in  very  small  glands,  or  even  to  one,  but  this  is  rare. 
These  glands  are  lodged  in  the  substance  of  the  corium.  Several  may 
open  into  the  same  hair  follicle,  surrounding  it  on  all  sides,  and  their 
size  is  not  regulated  by  the  magnitude  of  the  hair.  Thus,  some  of  the 
largest  are  connected  with  the  fine  downy  hairs  on  the  alae  of  the  nose 
and  other  parts  of  the  face,  and  there  they  often  become  unduly  charged 
with  pent-up  secretion.* 

* A few  years  ago  it  was.  discovered  by  Dr.  Gustavus  Simon,  that  the  sebaceous  and 
hair  follicles  were  infested  by  a worm,  which  he  has  described  and  delineated  in  Muller’s 


94 


HAIRS. 


The  sudoriferous  glands  or  sweat  glands. — These  are  seated  on  the 
under  surface  of  the  corium,  and  at  variable  depths  in  the  subcutaneous 


[Fig.  293. 


[Fig.  294. 


Sweat-gland  and  the  commencement  of  its 
duct: — a.  Venous  radicles  on  the  wall  of  the 
cell  in  which  the  gland  rests.  This  vein  anas- 
tomoses with  others  in  the  vicinity,  b.  Ca- 
pillaries of  the  gland  separately  represented, 
arising  from  their  arteries,  which  also  anasto- 
mose. The  blood-vessels  are  all  situated  on 
the  outside  or  deep  surface  of  the  tube,  in 
contact  with  the  basement  membrane. — Mag- 
nified 35  diameters. — Todd  and  Bowman.] 

adipose  tissue.  They  have  the 
appearance  of  small  round  reddish 
bodies,  each  of  which,  when  exa- 
mined with  the  microscope,  is 
found  to  consist  of  a fine  tube, 
coiled  up  into  a ball  (though 
sometimes  forming  an  irregular 
or  flattened  figure),  from  which 
the  tube  is  continued,  as  the  duct 
of  the  gland,  upwards  through 
the  true  skin  and  cuticle,  and 
opens  on  the  surface  by  a slightly 
widened  orifice.  The  duct,  as 
it  passes  through  the  epidermis, 
is  twisted  like  a corkscrew,  that 
is,  in  parts  where  the  epidermis 
is  sufficiently  thick  to  give  room 
for  this  ; lower  down  it  is  but  slightly  curved  (fig.  294).  Sometimes 
the  duct  is  formed  of  two  coiled-up  branches,  which  join  at  a short 
distance  from  the  gland.  The  tube,  both  in  the  gland  and  where  it 
forms  the  excretory  duct,  consists  of  an  outer  coat,  continuous  with 


Vertical  section  of  the  sole: — a.  Cuticle; 
the  deep  layers  (rete  mucosum)  more  coloured 
than  the  upper,  and  their  panicles  rounded  ; 
the  superficial  layers  more  and  more  scaly. 
b.  Papillary  siructure.  c.  Cutis,  d.  Sweat-gland, 
lying  in  a cavity  on  the  deep  surface  of  the 
skin,  and  imbedded  in  globules  of  fat.  Its 
duct  is  seen  passing  to  the  surface.  Magnified 
40  diameters. — Todd  and  Bowman.] 


Archiv.  for  1842.  Since  then,  further  interesting  details  respecting  this  curious  parasite, 
with  observations  on  its  development,  have  been  contributed  by  Mr.  E.  Wilson.  Phil. 
Trans.  1844. 


THE  SKIN. 


95 


the  cerium,  and  reaching  no  higher  than  the  surface  of  the  true  skin, 
and  an  epithelial  lining,  continuous  with  the  epidermis,  which  alone 
forms  the  twisted  part  of  the  duct.  The  outer  or  dermic  coat  is  formed 
by  simple  or  basement  membrane,  strengthened  by  fine  fibres  of  cellu- 
lar tissue.  On  carefully  detaching  the  cuticle  from  the  true  skin,  after 
its  connexion  has  been  loosened  by  putrefaction,  it  usually  happens 
that  the  cuticular  linings  of  the  sweat  ducts  get  separated  from  their 
interior  to  a certain  depth,  and  are  drawn  out  in  form  of  short  threads 
attached  to  the  under  surface  of  the  epidermis.  Each  little  sweat 
gland  is  supplied  with  a dense  cluster  of  capillary  blood-vessels. 

Sweat  glands  exist  in  all  regions  of  the  skin,  and  attempts  have  been  made  to 
determine  their  relative  amount  in  different  parts,  for  they  are  not  equally 
abundant  everywhere ; but  whde  it  is  easy  to  count  their  numbers  in  a given 
space  on  the  palm  and  sole,  the  numerical  proportion  assigned  to  them  in  most 
other  regions  must  be  taken  with  considerable  allowance.  According  to  Krause, 
nearly  2,800  open  on  a square  inch  of  the  palm  of  the  hand,  and  somewhat 
fewer  on  an  equal  extent  of  the  sole  of  the  foot.  He  assigns  rather  more  than 
half  this  number  to  a square  inch  on  the  back  of  the  hand,  and  not  quite  so 
many  to  an  equal  portion  of  surface  on  the  forehead,  and  the  front  and  sides  of 
the  neck;  then  come  the  breast,  abdomen,  and  fore-arm,  where  he  reckons 
about  1,100  to  the  inch,  and  lastly,  the  lower  limbs  and  the  back  part  of  the 
neck  and  trunk,  on  which  the  number  in  the  same  space  is  not  more  than  from 
400  to  600. 

The  size  of  the  sweat  glands  also  varies.  According  to  the  observer  last 
named,  the  average  diameter  of  the  round-shaped  ones  is  about  one-sixth  of 
a line ; but  in  some  parts  they  are  larger  than  this,  as  for  example,  in  the  groin, 
but  especially  in  the  axilla.  In  this  last  situation  Krause  found  the  greater 
number  to  measure  from  one-third  of  a line  to  a line,  and  some  nearly  two  lines 
in  diameter. 

Functions  and  vital  p'operties  of  the  skin. — The  skin  forms  a general  external 
tegument  to  the  body,  defining  the  surface,  and  coming  into  relation  with  foreign 
matters  externally,  as  the  mucous  membrane,  with  which  it  is  continuous  and  in 
many  respects  analogous,  does  internally.  It  is  also  a vast  emunctory,  by  which 
a large  amount  of  fluid  is  eliminated  from  the  system,  in  this  also  resembling 
certain  parts  of  the  mucous  membrane.  Under  certain  conditions,  moreover,  it 
performs  the  office  of  an  absorbing  surface,  but  this  function  is  greatly  restricted 
by  the  epidermis.  Throughout  its  whole  extent  the  skin  is  endowed  with  tactile 
sensibility,  but  in  very  different  degrees  in  different  parts.  On  the  skin  of  the  palm 
and  fingers,  which  is  largely  supplied  with  nerves  and  furnished  with  numerous 
prominent  papillae,  the  sense  attains  a high  degree  of  acuteness ; and  this  endow- 
ment, together  with  other  conformable  arrangements  and  adaptations,  invests  the 
human  hand  with  the  character  of  a special  organ  of  touch.  A certain,  though 
low  degree  of  vital  contractility,  seems  also  to  belong  to  the  skin.  This  shows 
itself  in  the  general  shrinking  of  the  skin  caused  by  naked  exposure  to  cold  and 
by  certain  mental  emotions,  and  producing  the  state  of  the  surface  named  “ cutis 
anserina,”  in  consequence  of  the  little  eminences  becoming  more  prominent. 
The  erection  of  the  nipple  is  probably  also  due  to  contractility.  The  scrotum,  as 
is  well  known,  becomes  obviously  shrunk  and  corrugated  by  the  application  of 
cold  or  mechanical  irritation  to  its  surface ; but  in  this  case  the  contraction  takes 
place  in  the  subcutaneous  tissue,  and  the  skin  is  puckered.  It  has  been  supposed 
by  Muller  and  others,  that  the  contraction  of  the  cutaneous  and  subcutaneous 
tissue,  in  the  different  cases  mentioned,  is  caused  by  contractile  fibres,  not  dif- 
fering in  structure  from  the  fibres  of  ordinary  cellular  tissue.  In  opposition  to 
this  opinion,  however,  it  has  been  clearly  proved  that  the  subcutaneous  tissue  of 
the  scrotum  contains  true  muscular  fibres  of  the  plain  variety,  as  already  men- 
tioned ; at  the  same  time,  it  has  not  yet  been  determined  whether  similar  mus- 
cular fibres  are  in  any  proportion  intermixed  with  those  which  constitute  the 
framework  of  the  corium. 


96 


THE  SKIN. 


Reproduction  of  shin. — When  a considerable  portion  of  the  skin  is  lost,  the 
breach  is  repaired  partly  by  a drawing  inwards  of  the  adjoining  skin,  and  partly 
by  the  formation  of  a dense  tissue,  less  vascular  than  the  natural  corium,  and  in 
which,  so  far  as  I know,  hairs  and  glands  are  not  reproduced,  so  that  some  deny 
that  the  cutaneous  tissue  is  regenerated.  Still  the  new  part  becomes  covered 
with  epidermis,  and  its  substance  sufficiently  resembles  that  of  the  corium  to 
warrant  its  being  considered  as  cutaneous  tissue  regenerated  in  a simple  form. 
I may  add,  tliat  in  small  breaches  of  continuity,  from  cuts  inflicted  in  early  life, 
the  uniting  part  sometimes  acquires  furrows  similar  to  those  of  the  adjoining 
surface. 


SECRETING  GLANDS. 


The  term  gland  has  been  applied  to  various  objects,  differing 
widely  from  each  other  in  nature  and  office,  but  the  organs  of  which 
it  is  proposed  to  consider  generally  the  structure,  in  the  present 
chapter,  are  those  devoted  to  the  function  of  secretion. 

By  secretion  is  meant  a process  in  an  organized  body,  by  which 
various  matters,  derived  from  the  solids  or  fluids  of  the  organism,  are 
collected  and  discharged  at  particular  parts,  in  order  to  be  further 
employed  for  special  purposes  in  the  economy,  or  to  be  simply  elimi- 
nated as  redundant  material  or  waste  products.  Of  the  former  case, 
the  saliva  and  gastric  juice,  and  of  the  latter,  which  by  way  of  dis- 
tinction is  often  called  “ excretion,”  the  urine  and  sweat  may  be  taken 
as  examples. 

Secretion  is  very  closely  allied  to  nutrition.  In  the  one  process,  as 
in  the  other,  materials  are  selected  from  the  general  mass  of  blood 
and  appropriated  by  solid  textures;  but  in  the  function  of  nutrition  or 
assimilation,  the  appropriated  matter  is  destined,  for  a time,  to  con- 
stitute part  of  the  texture  or  organ,  whereas  in  secretion  it  is  imme- 
diately discharged  at  a free  surface.  The  resemblance  is  most  striking 
in  those  cases  in  which  the  waste  particles  of  the  texture  nourished 
are  shed  or  cast  off  at  its  surface,  as  in  the  cuticle  and  other  epithelial 
tissues.  It  has  thus  been  common,  with  physiological  writers,  to 
designate  the  selection  and  deposition  of  material  which  takes  place  in 
nutrition  by  the  term  “nutritive  secretion,”  whilst  the  function  of 
which  we  have  here  to  consider  generally  the  organs,  is  named  simply 
“ secretion,”  or  sometimes,  when  necessary  for  the  sake  of  distinction, 
“ excretive  secretion.” 

In  man,  and  in  animals  which  possess  a circulating  blood,  that  fluid 
is  the  source  whence  the  constituents  of  the  secretions  are  proximately 
derived;  and  it  is  further  ascertained,  that  some  secreted  matters  exist 
ready  formed  in  the  blood,  and  require  only  to  be  selected  and  sepa- 
rated from  the  general  mass,  whilst  others  would  seem  to  be  prepared 
from  the  materials  of  the  blood,  by  the  agency  of  the  secreting  organ. 
Among  the  secreted  substances  belonging  to  the  former  category, 
several,  such  as  water,  common  salt,  and  albumen,  are  primary  con- 
stituents of  the  blood,  but  others,  as  urea,  uric  acid,  and  certain  salts, 
are  the  result  of  changes,  both  formative  and  destructive,  which  take 
place  in  the  solid  textures  and  in  the  blood  itself,  in  the  general  pro- 
cess of  nutrition.  Again,  as  regards  those  ingredients  of  the  secretions 
which  are  prepared  or  elaborated  in  the  secretory  apparatus,  it  is  to 
be  observed,  that  they  may  undergo  changes  in  organic  form,  as  well 
as  in  chemical  composition.  Evidence  of  this  is  afforded  by  the  solid 
corpuscles  found  in  many  secretions,  as  well  as  by  the  seminal  cells  and 
spermatozoa  produced  in  the  testicle. 

In  considering,  d priori,  the  structural  adaptations  required  in  a 
secreting  apparatus,  one  important  provision  which  immediately  sug- 

VOL.  II.  9 


98 


SECRETING  GLANDS. 


gesis  itself  is,  that  the  blood-vessels  should  approach  some  free  surface 
from  which  the  secretion  may  he  poured  out.  It  is  not,  however, 
necessary  that  the  vessels  should  open  on  the  secreting  surface,  seeing 
that  their  coals,  as  well  as  the  tissue  covering  them,  are  permeable  to 
liquids;  but,  to  insure  the  most  favourable  conditions  for  the  discharge 
of  fluid,  it  is  requisite  that  the  vessels  should  be  divided  into  their  finest 
or  capillary  branches,  and  that  they  should  be  arranged  in  close  order, 
and  as  near  as  possible  to  the  surface.  In  this  condition,  their  coats 
are  reduced  to  the  greatest  degree  of  tenuity  and  simplicity,  and  the 
blood,  being  divided  into  minute  streams,  is  more  extensively  and 
thoroughly  brought  into  contact  with  the  permeable  parietes  of  its 
containing  channels,  as  well  as  more  effectually  and,  by  reason  of  its 
slower  motion,  for  a longer  time  exposed  to  those  influences,  whether 
operating  from  within  or  without  the  vessels,  which  promote  transu- 
dation. 

It  seems  not  unreasonable  to  conceive  that  such  a simple  arrange- 
ment as  that  just  indicated  would  suffice  for  the  separation  of  certain 
substances  from  the  general  mass  of  the  blood;  for  the  coats  of  the 
vessels  and  tissue  superjacent  to  them  are  not  permeated  with  equal 
facility  by  all  its  constituents;  nay,  it  is  not  unlikely  tliat,  in  certain 
instances  of  secretion  actually  occurring,  the  elimination  of  fluid  is 
effected  without  the  necessary  aid  of  any  more  complicated  apparatus. 
Thus,  the  exhalation  of  carbonic  acid  and  watery  vapour  from  the 
interior  of  the  lungs  and  air-passages,  is  probably  produced  in  this 
simple  manner,  although  the  structure  of  the  exhaling  membrane  is, 
for  other  reasons,  complex ; and  the  discharge  of  fluid  into  cavities 
lined  by  serous  membranes,  which  is  known  to  be  preternaturally 
increased  by  artificial  or  morbid  obstruction  in  the  veins,  may  be  a 
case  of  the  same  kind. 

But  another  element  is  almost  always  introduced  into  the  secreting 
structure,  and  plays  an  important  part  in  the  secretory  process ; this  is 
the  nucleated  cell.  A series  of  these  cells,  which  are  usually  of  a 
spheroidal  or  polyhedral  figure,  is  spread  over  the  secreting  surface, 
in  form  of  an  epithelium,  which  rests  on  a simple  membrane,  named 
the  basement  membrane,  or  membrana  propria.  This  membrane, 
itself  extravascular,  limits  and  defines  the  vascular  secreting  surface; 
it  supports  and  connects  the  cells  by  one  of  its  surfaces,  whilst  the 
other  is  in  contact  with  the  blood-vessels,  and  it  may  very  possi- 
bly, also,  minister,  in  a certain  degree,  to  the  process  of  secretion, 
by  allowing  some  constituents  of  the  blood  to  pass  through  it  more 
readily  than  others.  But  the  cells  are  the  great  agents  in  selecting 
and  preparing  the  special  ingredients  of  the  secretions.  They  attract 
and  imbibe  into  their  interior  those  substances  which,  already  existing 
in  the  blood,  require  merely  to  be  segregated  from  the  common  store, 
and  concentrated  in  the  secretion,  and  they,  in  certain  cases,  convert 
the  matters  which  they  have  selected  into  new  chemical  compounds, 
or  lead  them  to  assume  organic  structure.  A cell  thus  charged  with 
its  selected  or  converted  contents  yields  them  up  to  be  poured  out  with 
the  rest  of  the  secretion,  the  contained  substance  escaping  from  it 
either  by  exudation,  or,  as  is  probably  more  common,  by  dehiscence 


SECRETING  GLANDS. 


99 


of  the  cell  wall,  which,  of  course,  involves  the  destruction  of  the  cell 
itself.  Cells  filled  with  secreted  matter  may  also  be  detached  and 
discharged  entire  with  the  fluid  part  of  the  secretion,  and,  in  all  cases, 
new  cells  speedily  take  the  place  of  those  which  have  served  their 
office.  The  fluid  effused  from  the  blood-vessels,  no  doubt  supplies 
matter  for  the  nutrition  of  the  secreting  structure,  besides  affording  the 
materials  of  the  secretion,  the  residue,  when  there  is  any,  being  ab- 
sorbed. 

Examples,  illustrative  of  the  secreting  agency  of  cells,  are  afforded 
both  by  plants  and  animals.*  Thus,  cells  are  found  in  the  liver  of 
various  animals,  and  especially  of  crustaceans  and  molluscs,  some  of 
which  contain  a substance  resembling  coloured  biliary  matter,  and 
others  particles  of  fat.  Also,  in  the  urinary  organ  of  molluscs,  cells 
are  seen  which  inclose  little  opaque  masses  of  uric  acid.  The  secre- 
tion of  the  sebaceous  follicles  in  man  often  contains  detached  cells 
filled  with  fat;  and,  according  to  Mr.  Goodsir’s  observation,  the  ink- 
bag  of  the  cuttle-fish  is  lined  with  an  epithelium,  the  constituent  cells 
of  which  are  charged  with  pigment,  similar  to  that  which  imparts  the 
dark  colour  to  the  inky  secretion.  This  last  instance,  as  well  as  the 
production  of  spermatozoa,  is  an  example  of  the  formation  of  new  pro- 
ducts within  secreting  cells,  a process  further  illustrated  in  plants, 
which  afford  abundant  and  decided  evidence  of  the  production  of 
young  cells,  spermatic  filaments,  starch  granules,  oil,  various  colour- 
ing matters,  and  other  new'  compounds,  in  the  interior  of  cells. 

Both  in  animals  and  plants,  the  individual  cells  which  are  associated 
together  on  the  same  secreting  surface,  may  differ  from  each  other  in 
the  nature  of  their  contents.  Thus,  Dr.  H.  Meckel  states,  that  in  the 
liver  of  mollusca  he  found  some  cells  containing  biliary  matter,  and 
others  containing  fat ; and  in  the  recent  soft  parts  of  the  epidermis  and 
its  appendages,  it  is  quite  common  to  see  cells  filled  with  pigment 
mixed  with  others  which  are  colourless. 

A secreting  apparatus,  effectual  for  the  purpose  which  it  is  essen- 
tially destined  to  fulfil,  may 

thus  be  said  substantially  to  Fig.  295. 

consist  of  a simple  membrane, 
named  the  membrana  propria 
orbasemenimembrane  (mark- 
ed a in  the  plan,  fig.  295),  sup- 
porting a layer  of  secreting 
cells  on  one  of  its  surfaces 
(indicated  by  the  dotted  line 
b,  in  the  figure),  w'hilst  finely  ramified  blood-vessels  are  spread  over 
the  other  (c).  But,  whilst  the  structure  remains  essentially  the  same, 
the  configuration  of  the  secreting  surface,  or  (w'hat  amounts  to  the 
same  thing)  of  the  supporting  basement  membrane,  presents  various 
modifications  in  different  secreting  organs.  In  some  cases  the  secret- 
ing surface  is  plain,  or,  at  least,  expanded,  as  in  various  parts  of  the 
serous,  synovial,  and  mucous  membranes,  which  may  be  looked  on  as 

* See  various  instances  of  animal  secreting  cells  adduced  by  Goodsir,  Bowman,  H. 
Meckel,  Dr.  T.  Williams,  and  others. 


Plan  of  a secreting  membrane,  a.  Membrana 
propria,  or  basement  membrane,  b.  Epithelium, 
composed  of  secreting  nucleated  cells,  c.  Layer  of 
capillary  blood-vessels. 


100 


SECRETING  GLANDS. 


examples  of  comparatively  simple  forms  of  secreting  apparatus;  but, 
in  other  instances,  and  particularly  in  the  special  secretory  organs 
named  glands,  the  surface  of  the  secreting  membrane  is  variously 
involved  and  complicated.  An  obvious,  and  no  doubt  a principal, 
purpose  of  this  complication  is  to  increase  the  extent  of  the  secreting 
surface  in  a secreting  organ,  and  thus  augment  the  quantity  of  secre- 
tion yielded  by  it.  No  connexion  has  been  clearly  shown  to  exist 
between  the  quality  of  the  secretion  and  the  particular  configuration, 
either  internal  or  external,  of  the  organ  ; on  the  other  hand,  we  know 
that  the  same  kind  of  secretion  that  is  derived  from  a complex  organ 
in  one  animal,  may  be  produced  by  an  apparatus  of  most  simple  form 
in  another. 

Keeping  now  in  view  that  the  more  immediate  purpose  of  the  com- 
plication of  the  secreting  membrane  is  to  augment  its  surface  within 
a comparatively  circumscribed  space,  two  principal  modes  suggest 
themselves  in  which  the  membrane  might  so  increase  its  extent, 
namely,  by  rising  or  advancing,  in  form  of  a prominent  fold  or  some 
otherwise  shaped  projection  (fig.  296,  d),  or  by  retiring,  in  form  of  a 
recess  (fig.  297,  g). 

The  first-mentioned  mode  of  increase,  or  that  by  projection,  is  not 

what  is  most  generally 
followed  in  nature,  still 
it  is  not  without  exam- 
ple, and,  as  instances, 
we  may  cite  the  Haver- 
sian fringes  of  the  syno- 
vial membranes,  the  uri- 
nary organ  of  the  snail, 
which  is  formed  of  mem- 
branous lamellae,  and 
perhaps,  also,  the  choroid  plexuses  in  the  brain,  and  the  ciliary  pro- 
cesses in  the  eyeball,  although  secretion  may  not  be  the  primary  office 
of  the  last-mentioned  structures.  In  most  of  these  cases,  the  mem- 
brane assumes  the  form  of  projecting  folds,  which,  for  the  sake  of  fur- 
ther increase  of  surface,  may  be  again  plaited  and  complicated,  or 
cleft  and  fringed,  at  their  borders  (fig.  296,  e,  f). 

The  plan  of  augmenting  the  secreting  surface  by  recession  or  in- 
version of  the  membrane,  in  form  of  a cavity,  is,  with  few  exceptions, 
that  generally  adopted  in  the  construction  of  secreting  glands.  The 
first  degree  is  represented  by  a simple  recess  (fig.  297,  g,  h),  and 
such  a recess,  formed  of  secreting  membrane,  constitutes  a simple 
gland.  The  shape  of  the  cavity  may  be  tubular  {g)  or  saccular  (li), 
and,  in  either  case,  it  is  called  indifferently  a crypt,  follicle,  or  lacuna, 
for  these  names  have  not  been  strictly  distinguished  in  their  applica- 
tion. Examples  of  these  sitnple  glands  are  found  in  the  mucous  mem- 
brane of  the  stomach,  intestines,  and  some  other  parts.  The  secreting 
surface  may  be  increased,  in  a simple  tubular  gland,  by  mere  length- 
ening of  the  tube,  in  which  case,  however,  when  it  acquires  consider- 
able length,  it  is  coiled  up  into  a ball  (fig.  297,  i),  so  as  to  take  up  less 
room,  and  afford  more  ready  access  to  its  compactly  ramified  blood- 


Fig.  296. 


Finn  to  show  augmentation  of  surface  by  formation  of  pro- 
cesses. n,b,c,as  in  preceding  figure,  d,  simple,  and  e,  f, 
branched  or  subdivided  processes. 


SECRETING  GLANDS. 


101 


vessels.  The  sweat  glands,  already  described,  and  the  ceruminous 
glands  of  the  ear,  are  instances  of  simple  glands  formed  of  a long  con- 
voluted tube.  But  the  great  means  adopted  for  further  increasing  the 
secreting  surface,  is  by  the  subdivision,  as  well  as  extension,  of  the 
cavity,  and  when  this  occurs 
the  gland  is  said  to  be  com- 
pound.  There  is,  however, 
a condition  which  might  be 
looked  on  as  a step  between 
the  simple  and  compound 
glands,  in  which  the  sides  or 
extremity  of  a simple  tube 
or  sac  become  pouched  or 
loculated  (fig.  297,  k,  1). 

This  form  might  be  named 
the  multilocular  crypt. 

In  the  compound  glands, 
the  subdivisions  of  the  se- 
creting cavity  may  assume 
a tubular  or  a saccular  form, 
and  this  leads  to  the  distinc- 
tion of  these  glands  into  the 
“ tubular,”  and  the  “ vesicu- 
lar,” “ cellular,”  or  “ race- 
mose.” 

The  racemose  or  vesicular 
compound  glands  (fig.  297, 
m),  contain  a multitude  of 
small  rounded  vesicles  or 
saccules,  opening,  in  little 
clusters,  into  the  extremities 
of  a branched  tube,  named 
the  excretory  duct.  The 
little  rounded  vesicles  are, 
as  usual,  formed  by  a proper 
or  basement  membrane,  and 
lined,  or  often  rather  filled,  Plansofexlension  of  secreting  membrane,  by  inversion 
«7itVi  coordfinn- r>olle  ffirr  OQ'7  or  recession  in  form  of  Cavities.  A.  Simple  glands,  viz., 
wun  secreting  cens  I^ng.zy  /,  ^,s,raight  tube,  A,  sac,  i,  coiled  tube.  b.  Multilocular 
71);  they  are  arranged  in  crypts,  a,  of  tubular  form,  l,  saccular,  c.  Racemose  or 
groups,  each  group  opening 

into  a commencing  branch  of  tached  with  o,  branch  of  duct  proceeding  from  it.  d. 
the  duct  and  clustering  round  tubular  gland, 

it;  or  it  might,  with  equal  truth,  be  said,  that  the  branches  of  the  duct 
are  distended  at  their  extremities  into  clusters  of  vesicular  dilatations. 
The  ultimate  branches  of  the  duct  open  into  larger  branches  (o),  these 
into  larger  again,  till  they  eventually  terminate  in  one  or  more 
principal  excretory  ducts  (m),  by  which  the  secretion  is  poured  out  of 
the  gland.  It  is  from  the  clustered  arrangement  of  their  ultimate 
vesicular  recesses  that  these  glands  are  named  “ racemose,”  and  they, 
for  the  most  part,  have  a distinctly  lobular  structure.  The  lobules  are 

9* 


102 


SECRETING  GLANDS. 


lield  together  by  the  branches  of  the  duct  to  which  they  are  appended, 
and  by  uniting  cellular  tissue,  which  also  supports  the  blood-vessels  in 
their  ramification.s.  The  larger  lobules  are  made  up  of  smaller  ones, 
these  of  still  smaller,  and  so  on,  for  several  successions.  The  smallest 
lobules  (fig.  297,  n),  consist  of  two  or  three  groups  of  terminal  vesi- 
cles, with  a like  number  of  ducts,  joining  into  an  immediately  larger 
ramuscule  (o),  which  issues  from  the  lobule;  and  a collection  of  the 
smallest  lobules,  united  by  cellular  tissue  and  vessels,  forms  one  of  the 
next  size,  which,  too,  has  its  larger  branch  of  the  duct,  formed  by  the 
junction  of  the  ramuli  belonging  to  the  ultimate  lobules.  In  this  way, 
the  whole  gland  is  successively  made  up,  the  number  of  its  lobules  and 
of  the  branches  of  its  duct  depending  on  its  size;  for  whilst  some 
glands  of  this  kind,  like  the  parotid  and  pancreas,  consist  of  innume- 
rable lobules,  connected  by  a large  and^many-branched  duct,  others, 
such  as  the  duodenal  glands  of  Brunner  and  many  mucous  glands, 
are  formed  of  but  two  or  three  ultimate  lobules,  or  even  of  a single 
one,  with  a duct,  minute  in  size,  and  sparingly  branched,  to  corre- 
spond. In  fact,  a small  racemose  gland  resembles  a fragment  of  a 
larger  one. 

A great  many  compound  glands,  yielding  very  different  secretions, 
belong  to  the  racemose  or  vesicular  class.  As  examples,  it  will  be 
sufficient  to  mention  the  pancreas,  the  salivary,  lachrymal,  and  mam- 
mary glands,  with  the  glands  of  Brunner  already  referred  to,  and  most 
of  the  small  glands  which  open  into  the  mouth,  fauces,  and  windpipe. 
From  the  description  given  of  their  structure,  it  will  be  understood  why 
the  term  “ conglomerate  glands”  has  been  applied  especially,  though  not 
exclusively,  to  this  class.  Their  smallest  lobules  were  called  acini,  a 
term  which  has  also  been  used  to  denote  the  saccular  recesses  in  the 
lobules,  and  indeed  the  word  acinus,  which  originally  meant  the  seed 
of  a berry  or  the  stone  of  a grape,  or  sometimes  the  grape  itself,  has 
been  so  vaguely  applied  by  anatomists,  that  it  seems  better  to  discard 
it  altogether. 

Of  the  tubular  compound  glands,  the  most  characteristic  examples 
are  the  testicle  and  kidney.  In  these  the  tubular  ducts  divide  again 
and  again  into  branches,  which,  retaining  their  tubular  form,  are 
greatly  lengthened  out.  The  branches  of  the  ducts  are,  as  usual, 
formed  of  a limitary  or  basement  membrane,  lined  by  epithelium,  and 
in  contact,  by  its  opposite  surface,  with  capillary  blood-vessels.  By 
the  multiplication  and  elongation  of  the  tubular  branches  a vast  extent 
of  secreting  surface  is  obtained,  whilst,  to  save  room,  the  tubes  are 
coiled  up  into  a more  or  less  compact  mass,  which  is  traversed  and 
held  together  by  blood-vessels,  and  sometimes,  also,  divided  into 
lobules  and  supported,  as  in  the  testicle,  by  fibro-cellular  partitions, 
derived  from  the  inclosing  capsule  of  the  gland.  In  consequence  of 
their  intricately  involved  arrangement,  it  is  difficult  to  find  out  how  the 
tubular  ducts  are  disposed  at  their  extremities.  It  seems  probable, 
however,  that  some  are  free,  and  simply  closed  without  dilatation,  and 
that  others  anastomose  with  neighbouring  tubes,  joining  with  them  in 
form  of  loops;  in  the  kidney,  little  round  tufts  of  fine  blood-vessels 


SECRETING  GLANDS. 


103 


project  into  terminal  or  lateral  dilatations  of  the  ducts,  but  without 
opening  into  them. 

The  human  liver  does  not  precisely  agree  in  structure  with  either 
of  the  above  classes  of  compound  glands.  Its  ducts,  which  are  neither 
coiled  nor  dilated,  would  seem  to  begin  within  its  lobules  in  form  of  a 
very  close  network,  occupying  the  interstices  of  the  reticular  capillary 
blood-vessels,  which  also  are  peculiar,  inasmuch  as  they  receive  and 
transmit  venous  blood. 

Lastly,  there  are  certain  anomalous  little  bodies,  connected  with  the 
mucous  membrane  of  the  intestines,  known  by  the  names  of  the  soli- 
tary and  the  agminated  glands,  which  differ  from  all  those  hitherto 
spoken  of,  inasmuch  as  they  are  small  saccules  without  an  opening, 
and  seem  to  discharge  their  contents,  from  time  to  time,  by  bursting. 
But  the  full  description  of  these  glands,  as  well  as  of  the  peculiarities 
in  the  structure  of  the  liver  and  kidney  above  referred  to,  belongs  to 
the  details  of  special  anatomy. 

Besides  blood-vessels,  the  glands  are  furnished  with  lymphatics,  but 
the  arrangement  of  these  within  the  compound  glands,  though  it  is 
most  probably  reticular,  has  not  been  fully  traced.  Branches  of  nerves 
have  also  been  followed,  for  some  way,  into  these  organs,  and  the 
well-known  fact,  that  the  flow  of  secretion  in  several  glands  is  affected 
by  mental  emotions,  shows  that  an  influence  is  exerted  on  secreting 
organs  through  the  medium  of  the  nerves.  It  has  not  been  ascertained 
how  the  ultimate  ramifications  of  the  nerves  are  disposed  of  in  the 
glandular  structure,  nor  how  they  are  related  to  its  more  immediate 
constituents. 

From  what  has  been  stated,  it  will  be  apparent  that  the  substance 
of  a gland  consists  of  the  ducts,  blood-vessels,  lymphatics,  and  a few 
nerves,  in  some  cases  connected  by  an  intervening  tissue.  In  the 
testicle  there  is  a very  small  amount  of  intermediate  cellular  tissue, 
which  with  the  aid  of  the  blood-vessels,  holds  the  tubules  but  feebly 
together,  so  that  the  structure  is  comparatively  loose,  and  readily 
admits  of  being  teased  out;  but  then  it  is  sufficiently  protected  and 
supported  by  the  fibrous  capsule  on  the  outside,  and  the  septa  within 
the  gland.  In  the  racemose  or  vesicular  glands,  there  is  a good  deal 
of  uniting  cellular  tissue,  which  surrounds  collectively  each  group  of 
vesicles,  binds  together  the  lobules,  and  supports  the  vessels  in  their 
ramifications.  The  substance  of  the  kidney  contains  scarcely  any 
distinctly  characterized  cellular  tissue,  unless  bundles  which  here  and 
there  accompany  the  larger  branches  of  vessels,  but,  according  to  Mr. 
Bowman,  there  is  more  or  less  of  a soft  amorphous  granular  matter 
among  the  tubules  and  blood-vessels,  which  binds  them  together, 
especially  in  the  pyramids,  where  they  have  a straight  course.  Paren- 
chyma is  a word  sometimes  employed  in  describing  the  glands,  though 
less  in  use  now  than  formerly.  It  has  sometimes  been  employed 
merely  to  denote  the  solid  part  of  a gland  composed  of  all  the  tissues 
already  mentioned ; at  other  times,  it  has  been  used  to  signify  any 
substance,  of  whatever  nature,  lying  between  the  ducts,  vessels,  and 
nerves.  In  this  last  sense,  the  parenchyma  is,  in  certain  glands,  re- 


104 


SECRETING  GLANDS. 


presented  by  cellular  tissue,  in  others,  as  the  kidney,  by  amorphous 
matter,  whilst  there  are  some  in  which  it  cannot  be  said  to  exist. 

Some  glands  have  a special  envelope,  as  is  the  case  with  the  kidney 
and  testicle;  others,  as  the  pancreas,  have  none. 

The  ducts  of  glands  ultimately  open  into  cavities  lined  by  mucous 
membrane,  or  upon  the  surface  of  the  skin.  They  are  sometimes 
provided  with  a reservoir,  in  which  the  secretion  is  collected,  to  be 
discharged  when  the  purposes  of  the  economy  or  the  convenience  of 
the  individual  demand.  The  reservoir  of  the  urine  receives  the  whole 
of  the  secreted  fluid ; in  the  gall-bladder,  on  the  other  hand,  only  a 
part  of  the  bile  is  collected.  The  vesiculse  seminales  afford  another 
example  of  these  appended  reservoirs.  The  ducts  are  constructed  of 
a basement  membrane  and  lining  of  epithelium,  and  in  their  smaller 
divisions  there  is  nothing  more,  but  in  the  larger  branches  and  trunks 
a fibro-vascular  layer  is  added,  as  in  the  ordinary  mucous  membrane, 
with  which  many  of  them  are  continuous,  and  with  which  they  all 
agree  in  nature.  A more  or  less  firm  outer  coat,  composed  of  cellular 
tissue,  comes,  in  many  cases,  to  surround  the  mucous  lining,  and 
between  the  two,  or,  at  any  rate,  outside  the  mucous  coat,  there  are 
in  many  ducts  muscular  fibres  of  the  plain  variety,  disposed  in  two 
layers,  in  the  more  internal  and  more  considerable  of  which  layers  the 
fibres  run  longitudinally,  and  in  the  other  circularly.  The  epithelium 
is  usually  composed  of  spheroidal  or  polyhedral  particles  at  the  com- 
mencement of  the  ducts,  and  is  columnar  in  the  rest  of  their  length, 
though  sometimes  flattened  or  scaly,  as  in  the  mammary  gland. 


ORGANS  OF  RESPIRATION. 


The  organs  of  respiration  consist  of  the  thorax  (already  described), 
the  IxLngs  and  the  windpipe.  The  larynx,  which  is  affixed  to  the  upper 
end  of  the  air-tube,  and  opens  above  into  the  pharynx,  will  be  sepa- 
rately described  afterw’ards. 

THE  TRACHEA  AND  BRONCHI. 

The  trachea  or  loindpiye,  a^rriPia,  arteria  aspera,)  the  com- 

mon air-passage  of  both  lungs,  is  an  open  tube  which  commences  at 
the  larynx  above,  and  divides  below  into  two  smaller  tubes,  named 
the  right  and  the  left  bronchus,  there  being  one  for  each  lung. 

The  trachea  is  placed  in  the  middle  line  of  the  body,  being  situated 
partly  in  the  neck  and  partly  in  the  thorax,  and  extends  from  the 
lower  border  of  the  cricoid  cartilage  of  the  larynx  on  a level  with  the 
fifth  cervical  vertebra,  to  opposite  the  third  dorsal  vertebra  in  the 
thorax,  where  it  is  crossed  in  front  by  the  arch  of  the  aorta,  and  at  or 
immediately  below  that  point  bifurcates  into  the  two  bronchi.  It 
usually  measures  from  four  inches  to  four  inches  and  a half  in  length, 
and  from  three  quarters  of  an  inch  to  one  inch  in  width  ; but  its  length 
and  width  are  liable  to  continual  variation,  according  to  the  position 
of  the  larynx  and  the  direction  of  the  neck  ; . moreover  it  usually 
widens  a little  at  its  lower  end,  and  its  diameter  is  always  greater  in 
the  male  than  in  the  female.  In  form  the  trachea  resembles  a cylin- 
der, rounded  in  front  and  at  the  sides,  but  flattened  behind.  Its 
rounded  portion  is  firm  and  resistant,  owing  to  that  part  of  its 
walls  containing  a series  of  horizontal  cartilaginous  rings,  which, 
however,  are  deficient  behind,  so  that  the  posterior  flattened  portion  is 
entirely  membranous. 

The  trachea  is  nearly  everywhere  invested  by  a loose  cellular  tis- 
sue, and  is  very  movable  on  the  surrounding  parts.  Both  in  the 
neck  and  in  the  thorax,  it  rests  behind  against  the  oesophagus,  which 
intervenes  between  it  and  the  vertebral  column,  and  towards  its  lowmr 
part  projects  somewhat  to  its  left  side.  The  recurrent  nerves  ascend 
to  the  larynx  between  these  two  tubes. 

In  the  neck,  the  trachea  is  situated  between  the  great  vessels,  its 
sides  being  close  to  the  common  carotid  arteries  ; at  its  upper  end  it 
is  embraced  by  the  lateral  lobes  of  the  thyroid  body,  the  middle  part 
or  isthmus  of  which  crosses  over  it  just  below  the  larynx.  It  is  also 
covered  in  front  by  the  sterno-thyroid  and  sterno-hyoid  muscles,  and 
in  the  small  interval  between  the  muscles  of  the  two  sides  by  the  deep 
cervical  fascia.  The  inferior  thyroid  veins  and  the  arteria  thyroidea 
ima  (of  Neubauer),  when  that  vessel  exists,  also  lie  upon  its  anterior 
surface ; whilst  at  the  root  of  the  neck,  in  the  episternal  notch,  the 


106 


STRUCTURE  OF  TRACHEA. 


innominate  artery  and  the  left  carotid  pass  obliquely  over  it  as  they 
ascend  to  gain  its  sides. 

In  the  thorax,  the  trachea  is  covered  by  the  first  piece  of  the 
sternum,  together  with  the  sterno-thyroid  and  sterno-hyoid  muscles; 
lower  down,  by  the  left  innominate  vein,  then  by  the  commencement 
of  the  innominate  artei'y  and  left  carotid,  which  pass  round  to  its 
sides,  next  by  the  arch  of  the  aorta  and  the  deep  cardiac  plexus  of 
nerves,  and  quite  at  its  bifurcation,  by  the  place  of  subdivision  of  the 
pulmonary  artery.  Placed  between  the  two  pleurae,  the  trachea  is 
contained  in  the  posterior  mediastinum,  and  has  on  its  right  side  the 
pleura  and  pneumogastric  nerve,  and  on  the  left,  the  left  carotid 
artery,  the  pneumogastric  and  its  recurrent  branch,  together  with 
some  cardiac  nerves. 

The  two  bronchi,  (fig.  207,  h,  h,)  named  from  their  relative  position 
right  and  left,  commence  at  the  bifurcation  of  the  trachea  behind  the 
arch  of  the  aorta,  and  proceed  laterally,  one  towards  the  root  or  place 
of  attachment  of  each  lung,  where  they  are  found  on  a plane  posterior 
to  the  pulmonary  arteries  and  veins.  They  difi'er  from  each  other  in 
length,  width,  direction,  and  connexion  with  other  parts.  The  right 
bronchus,  wider  but  shorter  than  the  left,  measuring  about  an  inch  in 
length,  passes  outw'ards  almost  horizontally  into  the  root  of  the  right 
lung  on  a level  with  the  fourth  dorsal  vertebra  : it  is  embraced  above 
by  the  vena  azygos,  which  hooks  forwards  over  it,  to  end  in  the  vena 
cava  superior;  the  right  pulmonary  artery  lies  at  first  below  it  and 
then  in  front  of  it.  The  left  bronchus,  smaller  in  diameter,  but  longer 
than  the  right,  being  nearly  two  inches  in  length,  inclines  obliquely 
downwards  and  outwards  beneath  the  arch  of  the  aorta,  to  reach  the 
root  of  the  left  lung,  which  it  enters  on  a level  with  the  fifth  dorsal 
vertebra,  that  is,  about  an  inch  lower  than  the  right  bronchus.  The 
left  bronchus  crosses  in  front  of  the  oesophagus  and  descending  aorta; 
the  arch  of  the  aorta  turns  backwards  and  to  the  left  over  it,  and  the 
left  pulmonary  artery  lies  first  above  it  and  then  on  its  anterior  sur- 
face. The  remaining  connexions  of  each  bronchus,  as  it  lies  within 
the  root  of  the  corresponding  lung,  and  the  mode  in  which  it  subdi- 
vides there  into  bronchia,  will  be  presently  described. 

In  form  the  bronchi  exactly  resemble  the  trachea  on  a smaller 
scale ; they  are  rounded  and  firm  in  front  and  at  the  sides,  where  they 
are  provided  with  imperfect  cartilaginous  rings,  and  they  are  flattened 
and  membranous  behind. 

Structure  of  the  Trachea. 

The  trachea  is  composed  of  a series  of  thin  horizontal  cartilages, 
resembling  in  form  imperfect  rings,  which  are  connected  together  by 
a continuous  membranous  tube,  consisting  chiefly  of  a fibrous  layer 
lined  in  its  interior  by  the  mucous  membrane  belonging  to  the  air  pas- 
sages. The  walls  of  the  trachea  also  contain  muscular  fibres,  elastic 
tissue,  and  glands,  besides  vessels,  nerves,  and  cellular  tissue. 

The  cartilages  and  fibrous  m.embrane. — The  cartilages  are  from 
sixteen  to  twenty  in  number.  Each  has  the  form  of  a ring  or  hoop 
imperfect  behind,  so  as  to  represent  rather  more  than  two-thirds  of  a 


CARTILAGES  OF  TRACHEA. 


107 


circle,  and  resembling,  when  removed  from  the  connecting  fibrous 
membrane,  the  letter  C.  Their  depth  from  above  downwards  is  from 
one  line  and  a half  to  two  lines,  and  their  thickness  half  a line.  The 
outer  surface  of  each  is  flat,  but  the  inner  surface  is  rounded  or  convex 
from  above  downwards : this  is  best  seen  upon  a vertical  section, 
which  is  thicker  in  the  middle  and  thinner  at  the  upper  and  lower 
edge.  They  are  held  together  by  a strong  fibrous  membrane  which 
connects  the  edges  of  the  adjacent  cartilages.  This  membrane  is 
elastic  and  extensible  in  a certain  degree,  and  not  only  occupies  the 
intervals  between  the  cartilages,  but  is  prolonged  over  their  outer  and 
inner  surfaces,  so  that  they  are,  as  it  were,  embedded  in  it.  The 
layer  covering  the  outer  side  of  the  rings  is  stronger  than  that  within 
them,  and  from  this  circumstance,  together  w'ith  the  roundness  of  their 
inner  surfaces,  they  maybe  felt  more  prominently  on  the  interior  than 
the  exterior  of  the  trachea. 

The  cartilages  terminate  abruptly  behind,  (fig.  308,  r.)  At  the 
back  of  the  trachea,  where  they  are  altogether  wanting,  the  fibrous 
membrane  (/)  is  continued  across  between  their  ends,  but  it  is  here 
looser  in  its  texture. 

The  first  or  highest  cartilage,  which  is  connected  by  the  fibrous 
membrane  with  the  lower  margin  of  the  cricoid  cartilage,  is  broader 
than  the  rest,  and  is  often  divided  at  one  end.  Sometimes  it  coalesces 
in  a greater  or  less  extent  with  the  cricoid  or  with  the  succeeding 
cartilage.  The  lowest  cartilage,  which  is  placed  at  the  bifurcation  of 
the  trachea  into  the  bronchi,  is  also  peculiar  in  shape : thus,  in  the 
middle  it  is  very  deep  and  thick,  owing  to  its  lower  border  being  pro- 
longed downwards,  and  at  the  same . time  bent  backwards,  so  as  to 
form  a curved  projection  between  the  two  bronchi ; whilst,  on  each 
side,  it  is  produced  into  a short  semicircular  or  imperfect  ring,  which 
embraces  the  commencement  of  the  corresponding  bronchus.  The 
cartilage  next  above  this  one  is  slightly  widened  in  the  middle  line. 
Of  the  other  cartilages,  it  is  found,  that  sometimes  the  extremities  of 
two  adjacent  ones  are  united  together,  and  that  not  unfrequently  a carti- 
lage is  divided  at  the  end  into  two  short  branches,  the  opposite  end  of 
the. next  one  being  likewise  bifurcated  so  as  to  maintain  the  parallelism 
of  the  entire  series.  The  use  of  these  cartilaginous  hoops  is  to  keep 
the  trachea  open,  a condition  essential  for  the  maintenance  of  the 
respiratory  function. 

Muscular  fibres. — Between  the  fibrous  and  the  mucous  membrane 
at  the  posterior  flattened  part  of  the  trachea,  there  is  found  a con- 
tinuous pale  reddish  layer,  consisting  of  transverse  muscular  fibres 
(fig.  308,  n),  which  pass  across,  not  only  between  the  posterior  ex- 
tremities of  the  cartilages,  but  opposite  the  intervals  between  the  rings 
also.  Those  which  are  placed  opposite  the  cartilages  are  attached  to 
the  ends  of  the  rings,  and  encroach  also  for  a short  distance  upon  the 
adjacent  part  of  their  inner  surface. 

These  fibres  belong  to  the  involuntary  class  of  muscular  fibres,  and 
are  destitute  of  striae.  They  are  best  seen  by  taking  away  the  fibrous 
membrane  and  the  small  glands  of  the  trachea  from  behind.  They 
can  approximate  the  ends  of  the  cartilages,  so  as  to  render  the  walls 
of  the  trachea  tense,  and  at  the  same  time  diminish  its  area. 


108 


THE  LUNGS  AND  PLEURA. 


Elastic  fibres. — Situated  immediately  beneath  the  tracheal  mucous 
membrane,  and  adhering  intimately  to  it,  are  numerous  longitudinal 
fibres  of  yellow  elastic  tissue.  They  are  found  all  round  the  tube, 
internal  to  the  cartilages  and  the  muscular  layer,  but  are  much  more 
abundant  along  the  posterior  membranous  part,  where  they  are  prin- 
cipally collected  into  distinct  longitudinal  bundles,  which  produce 
visible  elevations  or  flutings  of  the  mucous  membrane.  These  bundles 
are  particularly  strong  and  numerous  opposite  the  bifurcation  of  the 
trachea.  The  elastic  longitudinal  fibres  serve  to  restore  the  windpipe 
to  its  ordinary  length  after  it  has  been  stretched  in  its  movements. 

The  gla7ids. — The  trachea  is  provided  with  very  numerous  mucous 
glands,  the  constant  secretion  from  which  serves  to  lubricate  its  in- 
ternal surface.  The  largest  of  these  glands  are  small  roundish  lenti- 
cular bodies,  situated  at  the  back  part  of  the  tube,  lying  close  upon 
the  outer  surface  of  the  fibrous  layer,  or  occupying  little  recesses 
formed  between  its  meshes  (fig.  308)  : these  are  compound  glands  ; 
their  excretoi’y  ducts  pass  forwards  between  the  muscular  fibres  and 
open  on  the  mucous  membrane,  where  multitudes  of  minute  orifices 
are  perceptible.  Other  similar  but  smaller  glands  are  found  upon  and 
within  the  fibrous  membrane  between  the  cartilaginous  rings.  Lastly, 
there  appear  to  be  still  smaller  glands  lying  close  beneath  the  mucous 
coat. 

The  mucous  membrane. — This,  which  is  continuous  above  wdth  that 
of  the  larynx,  and  below  with  that  of  the  bronchi  and  their  ramifica- 
tions, is  smooth  and  of  a pale  pinkish-white  colour  in  health,  though 
when  congested  or  inflamed,  it  becomes  intensely  purple  or  crimson. 
It  is  covered  with  a ciliated  columnar  epithelium,  the  vibratile  move- 
ments of  which,  as  is  best  seen  at  the  back  of  the  trachea,  tend  to  drive 
the  mucous  secretion  upwards  towards  the  larynx. 

Vessels  and  nerves. — The  arteries  of  the  trachea  are  principally 
derived  from  the  inferior  thyroid  ; the  veins  enter  the  adjacent  plex- 
uses of  the  thyroid  veins.  The  nerves  come  from  the  trunk  and  re- 
current branches  of  the  pneumogastric,  and  from  the  sympathetic 
system. 

Structure  of  the  Bronchi. 

The  general  structure  of  the  bronchi  corresponds  with  that  of  the 
trachea  in  every  particular.  Their  cartilaginous  rings,  which  resem- 
ble those  of  the  trachea  in  being  imperfect  behind,  are,  however, 
shorter  and  narrower.  The  number  of  rings  in  the  right  bronchus 
varies  from  six  to  eight,  whilst  in  the  left,  the  number  is  from  nine  to 
twelve. 

The  bronchi  are  supplied  by  the  bronchial  arteries  and  veins,  and 
the  nerves  are  from  the  same  source  as  those  of  the  trachea. 

THE  LUNGS  AND  PLEURAE. 

The  lungs  (pulmones)  are  double  organs  situated  in  the  lateral  parts 
of  the  thorax,  one  right  and  the  other  left,  on  each  side  of  the  heart 
and  large  vessels,  from  which  they  are  separated  by  the  pericardium, 
and  by  the  two  layers  of  the  pleura  which  form  the  median  partition 


THE  PLEURA. 


109 


or  mediastinum  already  described  (vol.  i.  p.  469).  They  occupy  by  far 
the  larger  part  of  the  cavity  of  the  chest,  and  during  life  are  so  accu- 
rately adapted  to  its  varying  dimensions,  that  they  are  always  in  con- 
tact with  the  internal  surface  of  its  walls.  Each  lung  is  attached  at 
a comparatively  small  part  of  its  inner  or  median  surface  by  a part 
named  the  root,  and  by  a thin  membranous  fold  which  is  continued 
downwards  from  it.  In  other  directions  the  lung  is  free,  and  its  sur- 
face is  closely  covered  by  a serous  membrane,  proper  to  itself  and  to 
the  corresponding  side  of  the  thorax,  and  named  accordingly,  the  right 
or  left  pleura. 

THE  PLEURiE. 

The  pleurce  are  two  independent  serous  membranes  forming  two 
shut  sacs,  quite  distinct  from  each  other,  which  line  the  right  and  left 
sides  of  the  thoracic  cavity,  form  by  their  approximation  in  the  middle 
line  the  mediastinal  partition,  and  are  reflected  each  upon  the  root  and 
over  the  entire  free  surface  of  the  corresponding  lung. — There  is, 
therefore,  a right  and  a left  pleural  sac. 

Each  pleura  consists  of  a visceral  and  a parietal  portion,  the  former 
being  named  pleura  pulmonalis,  because  it  covers  the  lung;  and  the 
latter,  where  it  lines  the  ribs  and  intercostal  spaces,  being  called  pleura 
costalis.  The  parietal  portion  also  includes  that  part  which  covers 
the  upper  convex  surface  of  the  diaphragm,  and  the  median  layer 
which  enters  into  the  formation  of  the  mediastinum  and  is  reflected  on 
the  sides  of  the  pericardium. 

Owing  to  the  oblique  position  of  the  heart  downwards  and  towards 
the  left,  that  portion  of  the  mediastinum  which  extends  between  the 
pericardium  and  the  back  of  the  sternum,  named  the  anterior  medias- 
tinum, has  also  an  oblique  direction,  so  that  its  lower  end  is  found  a 
little  to  the  left  side  of  that  bone.  Somewhat  higher  than  the  middle 
of  the  sternum,  and  at  a little  distance  behind  its  second  piece,  the  two 
layers  of  the  anterior  mediastinum,  that  is,  the  two  pleurae  touch  each 
other  over  a small  space,  their  contiguous  surfaces  being  closely  con- 
nected together  by  cellular  tissue.  Above  and  below  this  point,  and 
also  immediately  behind  the  bone,  there  is  an  interval  between  the 
layers,  which  also  inclines  downwards  and  to  the  left,  and  contains 
certaiiq  parts  already  noticed.  Proceeding  backwards  from  the  ante- 
rior mediastinum,  the  two  pleurm  cover  the  sides  of  the  pericardium 
as  far  as  the  root  of  the  lung,  and  behind  that  part  pass  on  to  reach 
the  sides  of  the  vertebral  column,  thus  forming  the  posterior  medias- 
tinum, which,  with  its  important  contents,  has  been  previously  de- 
scribed. 

At  the  root  of  each  lung,  which  is  enclosed  by  its  own  pleura,  the 
visceral  and  parietal  portions  of  this  membrane  are  continuous  with 
each  other;  and  commencing  immediately  at  thfe  lower  border  of  the 
root,  there  is  found  a triangular  fold  or  duplicature  of  the  serous  mem- 
brane, extending  vertically  between  the  inner  surface  of  the  lung  and 
the  posterior  mediastinum,  and  reaching  down  to  the  diaphragm,  to 
which  it  is  attached  by  its  point:  this  fold,  which  serves  to  attach  the 
lower  part  of  the  lung,  is  named  ligamentum  latum  pulmonis. 

VOL.  II.  - 10 


110 


THE  LUNGS. 


The  upper  part  of  each  pleura,  which  receives  the  apex  of  the  cor- 
responding lung,  projects  in  the  form  of  a cul-de-sac  through  the  supe- 
rior aperture  of  the  thorax  into  the  neck,  reaching  an  inch,  or  even 
an  inch  and  a half  above  the  margin  of  the  first  rib,  and  passing  up 
between  the  lower  end  of  the  scaleni  muscles, — a small  slip  of  which 
arising  from  the  transverse  process  of  the  last  cervical  vertebra,  is  de- 
scribed by  Mr.  Sibson*  as  expanding  into  a dome-like  aponeurosis  or 
fascia,  v\hich  covers  or  strengthens  the  pleural  cul-de-sac,  and  is  at- 
tached to  the  whole  of  the  inner  edge  of  the  first  rib.  The  right  pleura 
is  generally  stated  to  reach  higher  in  the  neck  than  the  left,  but  in 
twenty  observations  recorded  by  Mr.  Hutchinson, f the  right  lung  was 
higher  in  ten  cases,  and  the  left  in  eight,  whilst  in  two  the  height  was 
equal  on  the  two  sides.  Owing  to  the  height  of  the  diaphragm  on  the 
right  side  (corresponding  with  the  convexity  of  the  liver),  the  right 
pleural  sac  is  shorter  than  the  left ; it  is  at  the  same  time  wider. 

Structure. — The  pleura  possesses  the  usual  characters  of  serous 
membrane.  The  costal  part  of  the  membrane  is  the  thickest,  and  may 
be  easily  raised  from  the  ribs  and  intercostal  spaces.  On  the  pericar- 
dium and  diaphragm  the  pleura  is  thinner  and  more  firmly  adherent, 
but  it  is  thinnest  and  least  easily  detached  upon  the  surface  of  the 
lungs. 

THE  LUNGS. 

Form. — Each  lung  is  of  a conical  shape,  having  its  base  turned 
downwards,  and  its  inner  side  much  flattened.  The  base  is  broad, 
concave,  and  of  a semilunar  form,  and  rests  upon  the  arch  of  the  dia- 
phragm. It  is  bounded  all  round  by  a thin  margin,  which  is  received 
in  the  interval  between  the  ribs  and  the  costal  attachment  of  the  dia- 
phragm ; and  it  reaches  much  lower  down  behind,  and  at  the  outer 
side  than  in  front  and  towards  the  middle  line.  The  apex  forms  a 
blunted  point,  and  as  already  mentioned,  reaches  into  the  root  of  the 
neck,  above  the  margin  of  the  first  rib,  where  it  is  separated  from  the 
first  portion  of  the  subclavian  artery  by  the  pleural  membrane. 

The  outer  surface  of  the  lung,  which  moves  upon  the  thoracic  pa- 
rietes,  is  smooth,  convex,  and  of  great  extent,  corresponding  with  the 
arches  of  the  ribs  and  costal  cartilages.  It  is  of  greater  depth  behind 
than  in  front.  The  posterior  border  is  obtuse  or  rounded,  and  is  re- 
ceived into  the  deep  groove  formed  by  the  ribs  at  the  side  of  the  ver- 
tebral column;  measured  from  above  downwards,  it  is  the  deepest 
part  of  the  lung.  The  anterior  border  is  thin  and  overlaps  the  peri- 
cardium, forming  a sharp  margin,  which  touches  the  sides  of  the  ante- 
rior mediastinum,  and,  opposite  the  middle  of  the  sternum,  is  separated 
during  inspiration  from  the  corresponding  margin  of  the  opposite  lung 
only  by  the  two  thin  and  adherent  layers  of  the  mediastinal  septum. 
The  inner  surface  of  the  lung,  which  is  flattened  or  concave,  is  turned 
towards  the  mediastinum,  and  is  adapted  to  the  convex  pericardium. 
Upon  this  surface,  somewhat  above  the  middle  of  the  lung,  and  con- 
siderably nearer  to  the  posterior  than  the  anterior  border,  is  the  part 
called  the  root,  where  the  bronchi  and  great  vessels  enter  and  pass 

* Op.  citat.  t Op.  cilat.  postea. 


CAPACITY  OF  LUNGS. 


Ill 


out.  Each  lung  is  traversed  by  a long  and  deep  fissure,  which  is  di- 
rected from  behind  and  above,  downwards  and  forwards.  It  com- 
mences upon  the  posterior  border  of  the  lung,  about  three  inches  from 
the  apex,  and  extends  obliquely  downwards  to  the  anterior  margin, 
penetrating  nearly  through  to  the  root  of  the  organ.  The  portion  of 
lung,  or  u'pper  lobe,  (fig.  207,'*  and  as  it  is  called,  which  is  situated 
above  this  fissure,  is  smaller  than  the  one  below  it,  and  is  shaped  like 
a cone  with  an  oblique  base,  whilst  the  lower  and  larger  lobe  and 
is  more  or  less  quadrilateral.'  In  the  right  lung  only  there  is  a second 
and  shorter  fissure,  which  runs  forwards  and  upwards  from  the  principal 
fissure  to  the  anterior  margin,  thus  marking  otf  a third  small  portion, 
or  middle  lobe  (“),  which  appears  like  an  angular  piece  separated  from 
the  anterior  and  lower  part  of  the  upper  lobe.  The  left  lung,  which 
has  no  such  middle  lobe,  presents  a deep  notch  in  its  anterior  border, 
into  which  the  apex  of  the  heart  (enclosed  in  the  pericardium)  is  re- 
ceived. Besides  these  differences  the  right  lung  is  shorter,  but  at  the 
same  time  wider  than  the  left,  the  perpendicular  measurement  of  the 
former  being  less,  owing  to  the  diaphragm  rising  higher  on  the  right 
side  to  accommodate  the  liver,  whilst  the  breadth  of  the  left  lung  is  nar- 
rowed, owing  to  the  heart  and  pericardium  encroaching  on  the  left 
half  of  the  thorax.  On  the  w'hole,  however,  as  is  seen  on  conpparisons 
of  weight,  the  right  is  the  larger  of  the  two  lungs. 

Weight,  dimensions,  and  capacity. — The  lungs  vary  much  in  size 
and  weight  according  to  the  quantity  of  blood,  mucus,  or  serous  fluid, 
they  may  happen  to  contain,  which  is  greatly  influenced  by  the  cir- 
cumstances immediately  preceding  death,  as  well  as  by  other  causes. 
The  weight  of  both  lungs  together,  as  generally  stated,  ranges  from 
thirty  to  forty-eight  ounces,  the  more  prevalent  weights  being  found 
between  thirty-six  and  forty-two  ounces.  The  proportion  borne  by 
the  right  lung  to  the  left  is  about  twenty-two  ounces  to  twenty,  sup- 
posing the  weight  of  both  to  be  forty-two  ounces.  The  lungs  are  not 
only  absolutely  heavier  in  the  male  than  in  the  female,  but  appear  to 
be  heavier  in  proportion  to  the  weight  of  the  body.  The  general  ratio 
between  the  weight  of  the  lungs  and  body,  in  the  adult,  fluctuates,  ac- 
cording to  the  estimate  of  Krause,  between  one  to  thirty-five  and  one 
to  fifty. 

The  following  tables,  deduced  from  Dr.  Reid’s  and  Mr.  Hutchinson’s  observa- 
tions, show  the  average  weights  of  the  right  and  left  lungs,  and  of  both  lungs 
together,  and  also  the  relative  weight  of  the  lungs  to  the  body  in  a certain  number 
of  adults,  of  both  sexes. 

AVERAGE  OF  TWENTY-NIKE  MALES  AND  TWENTY-ONE  FEMALES. (rEID.) 

MALE.  FEMALE. 

Right  lung 24  oz 17  oz. 

Left  lung 2 1 oz 1 5 oz. 


45  oz.  32  oz. 

AVERAGE  OF  TWENTY-FIVE  MALES  AND  THIRTEEN  FEMALES. — (rEID  AND  HUTCHINSON.) 

MALE.  FEMALE. 

Proportionate  weight  of  the  ) , , o-r  , . xo 

lungs  to  the  body j ^ ^o  37 1 to  43 

The  size  and  cubical  dimensions  of  the  lungs  are  influenced  so  much  by  their 


112. 


TEXTURE  OF  LUNGS. 


state  of  inflation,  and  are  therefore  so  variable,  that  no  useful  application  can  be 
made  of  the  measurements  sometimes  given.  The  quantity  of  air  which  they 
contain  under  different  conditions  has  been  investigated  by  many  inquirers,  whose 
statements  on  this  point,  however,  are  exceedingly  various.  The  volume  of  air 
contained  in  the  lungs  after  a forced  expiration  has  been  estimated  by  Goodwyn 
at  109  cubic  inches.  After  an  ordinary  expiration  it  would  seem  that  at  least  60 
cubic  inches  more  are  retained  in  the  chest,  giving  a total  of  169  cubic  inches  in 
that  condition  of  the  lungs.  The  amount  of  air  drawn  in  and  expelled  in  ordinary 
breathing,  has  been  very  differently  estimated  by  different  observers;  it  is  most 
probably  from  16  to  20  cubic  inches.  The  recent  extensive  and  important  re- 
searches of  Mr.  Hutchinson  on  this  subject,  have  led  him  to  the  conclusion  that, 
on  an  average,  men  of  mean  height,  between  five  and  six  feet,  can,  after  a com- 
plete inspiration,  expel  from  the  chest,  by  a forced  expiration,  225  cubic  inches, 
of  air  at  a temperature  of  60°.  This  quantity  is  called  by  Mr.  Hutchinson  the 
vital  capacity  of  the  lungs.  If  to  it  be  added  the  average  quantity  found  by  Good- 
wyn to  be  retained  in  the  lungs  after  complete  e.xpiration,  viz.,  109  cubic  inches, 
the  result  will  yield  335  cubic  inches  of  air  at  60°,  as  the  average  total  capacity 
of  the  respiratory  organs  for  air  in  an  adult  male  of  ordinary  height. 

The  vital  capacity  (or  difference  between  extreme  expiration  and  extreme  in- 
spiration) is  found  by  Hutchinson  to  bear  a singularly  uniform  relation  to  the 
height  of  the  individual,  increasing  eight  cubic  inches  for  every  additional  inch  of 
stature  above  five  feet.  Its  relations  with  the  weight  of  the  body  are  not  thus 
regularly  progressive,  for  it  appears  to  increase  about  one  cubic  inch  for  each 
additional  pound  between  the  weights  of  105  pounds  and  155  pounds,  or  7|  stone 
and  11  stone,  and  to  decrease  at  a similar  rate  between  the  weights  of  11  and  14 
stone,  or  155  and  200  pounds.  From  the  age  of  15  to  35  years  the  vital  capacity 
continues  to  advance  with  the  growth  and  activity  of  the  frame,  but  between 
the  ages  of  35  and  65  it  diminishes  at  the  rate  of  upwards  of  one  cubic 
inch  per  annum.  This  differential  or  vital  capacity  is  by  no  means  in  proportion 
to  the  size  of  the  thorax,  whether  that  be  estimated  by  the  circumference  of  the 
chest,  or  by  the  sectional  area  of  its  base,  or  by  its  absolute  capacity,  as  ascertained 
by  measuring  its  cubical  contents  after  death.  It  is  found  rather,  that  the  vital 
capacity  is  strictly  commensurate  with  the  extent  of  the  thoracic  movements,  and  with 
the  integrity  of  the  lungs  themselves ; so  that  in  phthisis,  for  example,  it  becomes 
reduced  by  10  to  70  per  cent,  according  to  the  .stage  of  the  disease.  Changing 
from  the  erect  to  the  sitting  posture  is  accompanied  by  a diminution  of  the  vital 
capacity,  which  in  one  case  fell  from  260  cubic  inches  to  255  cubic  inches,  and 
on  lying  down  it  was  further  diminished  to  230  cubic  inches  in  the  supine,  and 
220  cubic  inches  in  the  prone  position  of  the  body.  Lastly,  it  is  lowered  by  from 
12  to  20  cubic  inches,  by  the  presence  of  a full  meal  in  the  stomach.* 

Texture  and  consistence. — The  substance  of  the  lung  is  of  a light 
porous  spongy  structure,  and,  when  healthy,  is  buoyant  in  water;  but 
in  the  fetus,  before  respiration  has  taken  place,  and  also  in  cases  of 
congestion  or  consolidation  from  disease,  the  entire  lungs,  or  portions 
of  them,  will  sink  in  that  fluid.  The  specific  gravity  of  a healthy  lung, 
as  found  after  death,  varies  from  345  to  740,  water  being  1000.  When 
the  lung  is  fully  distended  its  specific  gravity  is  126,  whilst  that  of  the 
pulmonary  substance,  entirely  deprived  of  air,  is  1 056.  (Krause.)  When 
squeezed,  the  lungs  impart  to  the  finger  a crepitant  sensation,  which 
is  accompanied  by  a peculiar  noise,  both  effects  being  owing  to  the 
air  contained  in  the  tissue.  On  cutting  into  the  lung,  the  same  crepi- 
tation is  heard,  and  there  exudes  from  the  cut  surface  a reddish  frothy 
fluid,  which  is  partly  mucus  from  the  air-tubes  and  air-cells,  and 
partly  a serous  exudation,  tinged  with  blood  and  rendered  frothy  by 

* See  Mr.  Hutchinson’s  Papers,  (Journal  of  Statistical  Society,  Aug.  1844,  and  Medico. 
Chirg.  Transactions,  vol.  xxix.  1846,)  for  further  details,  for  a description  of  the  mode  of 
measuring  the  vital  capacity,  and  of  the  application  of  this  measurement  as  a test  of  the 
health. 


STRUCTURE  OF  THE  LUNGS. 


113 


the  admixed  air.  This  fluid  escapes  in  largest  quantity  from  the  pos- 
terior portion  of  the  lung. 

The  pulmonary  tissue  is  endowed  with  great  elasticity,  in  conse- 
quence of  which,  the  lungs  collapse  to  about  one-third  of  their  bulk, 
when  the  thorax  is  opened  and  the  resistance  offered  by  the  walls  of 
that  cavity  to  the  atmospheric  pressure  on  their  outer  surface  is  in  this 
way  removed.  Owing  to  this  elasticity  also,  the  lungs,  when  artifi- 
cially inflated  out  of  the  body,  resume  their  previous  volume  if  the  air 
be  again  allowed  to  escape. 

Colour. — In  infancy  the  lungs  are  of  a pale  rose-pink  colour,  which 
might  be  compared  to  blood-froth ; but  as  life  advances  they  become 
darker,  and  are  mottled  or  variegated  with  spots,  patches,  and  streaks 
of  dark  slate-colour,  which  sometimes  increase  to  such  a degree  as  to 
render  the  surface  uniformly  black.  The  dark  colouring  matter  to 
which  this  is  owing  is  deposited  mostly  near  the  surface  of  the  lung ; 
it  is  not  found  so  abundantly  in  the  deeper  substance.  It  exists  some- 
times in  the  air-cells,  and  on  the  coats  of  the  larger  vessels.  Its  quantity 
increases  with  age,  and  is  said  to  be  less  abundant  in  females  than  in 
men.  In  persons  who  follow  the  occupation  of  colliers,  the  lungs  are 
often  intensely  charged  with  black  matter.  The  black  colouring  sub- 
stance of  the  lung  is  unlike  the  black  pigment  of  the  choroid  coat  of 
the  eye  or  of  the  negro’s  skin,  for  it  is  not  destroyed  by  the  action  of 
chlorine.  It  seems  to  be  a carbonaceous  mixture,  consisting  of  car- 
bon and  some  animal  matter.  A black  substance  of  precisely  the 
same  nature  is  found  in  the  bronchial  glands. 

Opinions  differ  as  to  the  source  of  this  carbonaceous  deposit ; some  have  con- 
tended that  it  is  introduced  into  the  lungs  from  without,  by  the  inhalation  of 
minute  particles  of  carbon  floating  in  the  air:  the  very  dark  colour  of  the  lungs 
of  colliers  has  been  supposed  to  favour  this  view,  but  it  is  by  no  means  established. 
On  the  contrary,  it  is  supposed  by  many  that  its  existence  is  in  some  way  con- 
nected with  the  chemical  changes  incidental  to  the  respiratory  process, — that,  for 
example,  it  may  consist  of  carbon  eliminated  from  the  blood,  not  as  carbonic  acid, 
but  in  the  form  of  a solid  deposit  within  the  pulmonary  tissue. 

STRUCTURE  OF  THE  LUNGS. 

The  lungs  are  composed  of  an  external  or  serous  coat,  a subserous 
cellular  layer,  and  of  the  pulmonary  substance.  Beneath  the  serous 
covering,  which  has  been  already  noticed,  is  a thin  layer  of  subserous 
cellular  membrane  mixed  with  much  elastic  tissue.  It  is  continuous 
with  the  cellular  tissue  in  the  interior  of  the  lung,  and  has  been  de- 
scribed as  a distinct  coat  under  the  name  of  the  second  or  inner  layer 
of  the  pleura.  In  the  lungs  of  the  lion,  seal,  and  leopard,  this  subse- 
rous layer  forms  a very  strong  membrane,  composed  principally  of 
elastic  tissue. 

The  substance  of  the  lung  is  composed  of  numerous  small  lobules 
which  are  attached  to  the  ramiffcations  of  the  air-tubes,  and  are  held 
together  by  those  tubes,  by  the  blood-vessels,  and  by  an  interlobular 
cellular  tissue.  These  lobules  are  of  various  sizes,  the  smallest  uniting 
into  larger  ones;  they  are  polyhedral,  or  bounded  by  flattened  sides, 
and  are  thus  compactly  fitted  to  each  other  and  to  the  larger  air-tubes 

10* 


114 


PULMONARY  VESSELS. 


and  vessels  of  the  lungs.  On  the  surface  of  the  organ  they  are  pyra- 
midal, with  a lozenge-shaped  base  turned  outwards,  from  half  a line 
to  a line  in  diameter:  in  the  interior  of  the  lung  they  have  many  sides, 
and  are  of  various  shapes.  Though  mutually  adherent,  they  are  quite 
distinct  one  from  the  other,  and  may  be  readily  separated  by  dissec- 
tion in  the  lungs  of  young  animals,  and  in  those  of  the  human  foetus. 

The  interlobular  cellular  tissue  which  invests  these  lobules  and  con- 
nects them  together,  and  is  continuous  with  the  sub-pleural  cellular 
membrane,  is  very  fine.  It  is  generally  moistened  with  serosity,  is 
traversed  by  numerous  lymphatic  vessels,  and  contains  no  fat.  In 
one  form  of  disease  of  the  lung,  named  interlobular  emphysema,  this 
intermediate  tissue  becomes  inflated  with  air,  which  has  escaped  by 
rupture  from  tlie  interior  of  the  lobules.  By  forcing  air  beneath  the 
serous  coat  of  the  lung,  this  condition  may  be  imitated  after  death; 
and  in  either  case  the  lozenge-shaped  bases  of  the  larger  lobules  may 
be  seen  on  the  surface  of  the  organ  bounded  by  elevated  lines  formed 
by  the  inflated  interlobular  tissue. 

These  small  pulmonary  lobules  may  be  regarded  as  lungs  in  minia- 
ture, the  same  elements  entering  into  their  composition  as  form  the 
lung  itself.  The  structure  of  a single  lobule  represents  in  fact  that  of 
the  entire  organ,  each  lobule,  besides  its  investment  of  cellular  mem- 
brane, being  made  up  of  the  following  constituents:  the  air-tubes  and 
their  terminating  cells,  the  pulmonary  and  bronchial  blood-vessels,  with 
lymphatics,  nerves,  and  interstitial  cellular  tissue.  The  diflerent  ves- 
sels and  nerves  just  enumerated  enter  the  lung  by  its  root.  Up  to  that 
point  the  air-tubes,  or  right  and  left  bronchi,  have  already  been  traced, 
and  the  bronchial  arteries  and  veins,  and  the  lymphatics  have  also  been 
elsewhere  described.  We  will  now  follow  the  pulmonary  vessels  up 
to  the  same  point. 

PULMONARY  ARTERY  AND  VEINS.  ' 

The  pulmonary  artery,  (fig.  207,®,)  is  a short  wide  vessel,  which 
carries  the  dark  blood  from  the  right  side  of  the  heart  to  the  lungs. 
It  arises  from  the  infundibulum  or  conus  arteriosus  of  the  right  ven- 
tricle, and  passes  for  the  space  of  nearly  two  inches  upwards,  and  at 
the  same  time  backwards  and  to  the  left  side,  to  reach  the  concavity 
of  the  aortic  arch,  where  it  bifurcates  into  its  right  and  left  branches, 
a,  a.  The  mode  of  attachment  of  the  pulmonary  artery  to  the  base 
of  the  ventricle  has  already  been  fully  noticed.  At  each  side  of  its 
commencement  is  the  corresponding  coronary  artery  springing  from 
the  aorta,  and  in  contact  with  its  sides  are  the  two  auricular  ap- 
pendages. It  is  at  first  in  front  of  the  aorta,  and  conceals  the  origin 
of  that  vessel ; but  higher  up,  where  it  lies  in  front  of  the  left  auricle, 
it  crosses  to  the  left  side  of  the  ascending  aorta,  and  is  finally  placed 
beneath  the  transverse  part  of  the  arch.  The  pulmonary  artery  and 
the  aorta  are  connected  together  by  the  serous  layer  of  the  pericardium, 
which  for  the  space  of  about  two  inches  forms  a single  tube  around 
both  vessels.  Rather  to  the  left  of  its  point  of  bifurcation  it  is  con- 
nected to  the  under  side  of  the  aortic  arch  by  means  of  a short  fibrous 


ROOT  OF  THE  LUNGS. 


115 


cord,  which  passes  obliquely  upwards,  backwards,  and  to  the  left. 
This  is  the  remains  of  a large  vessel  peculiar  to  the  foetus,  named  the 
ductus  arteriosus,  which  has  been  previously  described. 

The  two  branches  of  the  ■pulmonary  artery. — The  right  branch, 
longer  and  somewhat  larger  than  the  left,  runs  almost  transversely 
outwards  behind  the  ascending  aorta  and  the  superior  vena  cava  into 
the  root  of  the  right  lung.  The  left  branch,  shorter  than  the  right, 
passes  horizontally  in  front  of  the  descending  aorta  and  left  bronchus 
into  the  root  of  the  left  lung. 

Pulmonary  Veins. — The  pulmonary  veins,  (fig.  207,  v,  u,)  which  con- 
vey the  red  blood  back  from  the  lungs  to  the  left  side  of  the  heart, 
ultimately  converge  mio  four  short  venous  trunks,  w'hich  are  found 
two  on  each  side  in  the  root  of  the  corresponding  lung.  The  two 
veins  of  the  right  side,  which  are  longer  than  those  of  the  left,  pass 
below  the  right  pulmonary  artery,  and  behind  the  superior  vena  cava, 
the  right  auricle,  and  the  aorta,  to  enter  the  left  auricle.  The  two  left 
pulmonary  veins  reach  the  same  cavity  after  a shorter  course,  passing 
in  front  of  the  descending  aorta. 

Root  of  the  Lung. 

The  root  of  each  lung  is  composed  of  the  bronchus  and  the  large 
blood-vessels,  together  with  the  nerves,  lymphatic  vessels  and  glands, 
all  of  which  parts  are  closely  connected  together  by  cellular  tissue, 
and  are  enclosed  in  a sheath  formed  by  the  reflection  of  the  pleura. 

The  root  of  the  right  lung  lies  behind  the  superior  vena  cava  and 
part  of  the  right  auricle,  and  below  the  azygos  vein,  which  arches 
over  it  to  enter  the  superior  cava.  That  of  the  left  lung  passes  below 
the  arch  of  the  aorta,  and  in  front  of  the  descending  aorta.  The 
phrenic  nerve  descends  in  front  of  the  root  of  each  lung,  and  the 
pneumogastric  nerve  behind,  whilst  the  ligamentum  latum  pulmonis 
is  continued  from  the  lower  border.  The  bronchus,  together  with  the 
bronchial  arteries  and  veins,  the  lymphatics  and  lymphatic  glands,  are 
placed  on  a plane  posterior  to  the  great  blood-vessels;  the  pulmonary 
artery  lies  more  forward  than  the  bronchus,  and  to  a great  extent 
conceals  it,  whilst  the  pulmonary  veins  are  still  further  in  advance. 
The  pulmonary  plexuses  of  nerves  lie  on  the  anterior  and  posterior 
aspect  of  the  root  beneath  the  pleura,  the  posterior  being  the  larger  of 
the  two. 

The  order  of  position  of  the  great  air-tube  and  pulmonary  vessels 
from  above  downwards  differs  on  the  two  sides  (see  fig.  207);  for 
whilst  on  the  right  side  the  bronchus  is  highest  and  the  pulmonary  artery 
next,  on  the  left,  the  air-tube,  in  getting  beneath  the  arch  of  the  aorta, 
has  to  pass  below  the  level  of  the  left  pulmonary  artery,  which  is  the 
highest  vessel.  On  both  sides  the  pulmonary  veins  are  the  lowest  of 
the  three. 

Before  entering  the  substance  of  the  lung,  the  bronchus  divides  into 
two  branches,  an  upper  and  a lower,  one  being  intended  for  each 
corresponding  lobe.  The  lower  branch  is  the  larger  of  the  two,  and 
on  the  right  side  gives  off  a third  small  branch  which  enters  the 


IIG 


THE  AIR-TUBES. 


middle  lobe  of  that  lung.  The  subsequent  ramifications  of  the  bronchi 
through  the  lungs  have  been  distinguished  by  the  name  of  bronchia.* 

The  pulmonary  artery  also  divides,  before  penetrating  the  lung  to 
which  it  belongs,  into  two  branches,  of  which  the  lower  is  the  larger 
and  supplies  the  lower  lobe.  The  upper  of  these  two  branches,  gives 
the  branch  to  the  middle  lobe.  A similar  arrangement  prevails  in 
regard  to  the  right  pulmonary  veins,  the  upper  one  of  which  is  foi'med 
by  branches  proceeding  from  the  superior  and  middle  lobes  of  the 
ri  fht  lun^^. 

O O 

Arrangement  and  Structure  of  Parts  within  the  Lung. 

The  Air-tubes. — The  principal  subdivisions  of  the  bronchi,  go  on 
dividing  and  subdividing  in  succession  into  smaller  and  smaller  tubes, 
named  generally  the  bronchia  or  the  bronchial  tubes,  which  diverge 
through  the  lung  in  all  directions,  and  never  anastomose.  The  pre- 
vailing form  of  division  is  dichotomous;  but  sometimes  three  branches 
arise  together,  and  often  lateral  branches  are  given  off  at  intervals 
from  the  sides  of  a main  trunk.  The  larger  branches  diverge  at 
rather  acute  angles,  but  the  more  remote  and  smaller  ramifications 
spring  more  and  more  obtusely.  After  a certain  stage  of  subdivision, 
each  bronchial  tube  is  reduced  to  a very  small  calibre,  and,  forming 
what  has  been  termed  a lobular  bronchial  tube,  enters  a distinct  pul- 
monary lobule,  within  which  it  undergoes  still  further  division,  and  at 
last  ends  in  the  small  cellular  recesses  named  the  air  cells  or  pulmonary 
cells.  It  follows,  therefore,  that  a multitude  of  air-cells,  supported  and 
invested  by  cellular  tissue  and  opening  into  the  finest  branches  of  a 
lobular  bronchial  tube,  constitute  together  with  vessels  and  nerves 
a pulmonary  lobule, — that  several  of  these  combined  together  form  a 
larger  lobule, — and  that  a large  number  of  these  again  are  aggregated 
together  to  form  a lobe. 

Within  the  lungs  the  air-tubes  are  not  flattened  behind  like  the 
bronchi  and  trachea  without,  but  form  completely  circular  tubes. 
Hence,  although  they  contain  the  same  elements  as  the  large  air- 
passages,  reduced  gradually  to  a state  of  tenuity,  they  possess  certain 
peculiarities  of  structure.  Thus,  the  cartilages  no  longer  appear  as 
imperfect  rings  running  only  upon  the  front  and  lateral  surfaces  of  the 
air-tube,  but  are  scattered  over  all  sides  of  the  tube  in  the  form  of 
irregularly-shaped  plates  of  various  sizes,  adapted  as  it  were  to  each 
other.  These  cartilaginous  laminae  are  most  marked  at  the  points  of 
division  of  the  bronchia,  where  they  form  a sharp  concave  ridge  pro- 
jecting inwards  into  the  tube.  They  may  be  traced,  becoming  how- 
ever rarer  and  rarer,  and  of  course  greatly  reduced  in  size,  as  far  as 
those  divisions  of  the  bronchia,  which  are  only  one-fourth  of  a line  in 
diameter,  beyond  which  the  tubes  are  entirely  membranous.  The  use 
of  these  cartilages  is  evidently  to  keep  the  air-tubes  open ; and  the 
reason  why  they  are  not  found  in  the  finest  branches  is  probably 
because  these  can  never  be  completely  emptied  of  air.  The  fibrous 
coat  extends  to  the  very  smallest  tubes,  becoming  thinner  by  degrees 
and  degenerating  into  cellular  tissue.  The  mucous  membrane,  which 

* “ Eos  ramos  veteres  bronchia,  syringes  et  aortas  dixerunt.”  Haller,  Elem.  Phys. 


THE  AIR-CELLS. 


117 


extends  throughout  the  whole  system  of  air-passages,  and  is  continuous 
with  that  lining  the  air-cells,  is  also  thinner  than  in  the  trachea  and 
bronchus,  but  it  retains  its  ciliated  columnar  epithelium.  The  yellow 
longitudinal  bundles  of  elastic  fibres  are  very  distinct  in  both  the  large 
and  small  bronchia,  and  may  be  followed  as  far  as  the  tube  can  be 
laid  open.  The  muscular  fibres,  which  in  the  trachea  and  bronchi 
are  confined  to  the  back  part  of  the  tube,  here  surround  it  with  a con- 
tinuous layer  of  annular  fibres,  lying  inside  the  irregular  cartilaginous 
plates;  they  are  found,  however,  beyond  where  the  cartilages  exist, 
and  appear  as  irregular  annular  fasciculi  even  in  the  smallest  tubes: 
they  are  pale  and  unstriped,  and  have  all  the  characters  of  the  involun- 
tary muscular  fibres. 

The  Air-cells,  or  Pulmonary  cells. — These  cells,  in  which  the  finest 
ramifications  of  each  lobular  bronchial  tube  ultimately  terminate,  are 
in  the  natural  state  always  filled  with  air.  They  are  readily  seen  on 
the  surface  and  upon  a section  of  a lung  which  has  been  inflated  with 
air  and  dried;  also  upon  portions  of  fcetal  or  adult  lung  injected  with 
mercury.  In  the  lungs  of  some  animals,  as  of  the  lion,  cat,  and  dog, 
they  are  very  large,  and  are  distinctly  visible  on  the  surface  of  the 
organ.  In  the  adult  human  lung  they  vary  from  ^00  of  an 

inch  in  diameter;  they  are  larger  on  the  surface  than  in  the  interior, 
and  largest  towards  the  thin  edges  of  tile  organ : they  are  also  said  to 
be  very  large  at  the  apex  of  the  lung.  Their  dimensions  go  on  in- 
creasing from  birth  to  old  age,  and  they  are  larger  in  men  than  in 
women.  In  vesicular  emphysema,  and  in  asthmatic  persons,  they  are 
unnaturally  and  sometimes  enormously  increased  in  size. 

Very  different  opinions  as  to  the  mode  of  comUaunication  of  the  air- 
cells  with  each  other  and  their  connexion  with  the  bronchial  tubes 
have  been  entertained.  All  anatomists  are  now  agreed  that  the  cells 
of  one  lobule,  isolated  by  its  investing  membrane,  do  not  communicate 
with  those  of  another.  Some,  however,  maintain  that  the  cells  w'ilhin 
each  lobule  communicate  freely  by  lateral  anastomoses,  or  even  so  as 
to  form  a labyrinth  of  short  canals,  enclosed  by  the  proper  membrane 
of  the  lobule  and  opening  into  its  bronchial  tube.  By  others  again,  it 
is  held  that  the  air-cells  do  not  communicate  directly,  but  are  the  ter- 
minations of  the  air-tubes,  which  ramify  like  a tree  without  anasto- 
mosing, and  have  been  supposed  to  end  either  in  bunches  of  blind 
dilated  extremities  (Willis),  or  in  very  short  hemispherical  pullulations, 
which  are  scarcely  if  at  all  dilated  (Reisseissen). 

[Fig.  298  represents  groups  of  air-cells,  of  the  size 
of  nature,  from  an  emphysematous  lung.  I.  A group 
of  air-cells  laid  open  and  exhibiting  the  fact  that 
there  is  no  lateral  intercommunication.  2.  Two  air- 
cells;  the  one  to  the  left  exhibits  its  bronchiolar  ori- 
fice. 3.  Another  group;  to  the  left  is  represented 
two  cells  freely  communicating  from  the  partition 
being  ruptured  by  over-distension;  and  between  the 
two  cells  to  the  right  is  observed  some  inflated 
areola;  of  areolar  tissue. — J.  L.] 

[There  are  two  sources  of  error  which  may  lead  to  the  opinion  that  the  air-cells 
of  the  lungs  directly  and  freely  intercommunicate : one  is  the  liability  of  con- 
founding intercellular  areolar  tissue  when  mfiated  with  the  air-cells  themselves ; 


[Fig.  298. 


118 


THE  AIK-CELLS. 


the  other,  is  the  liability  of  mistaking  the  bronchioles  for  air-cells.  If  all  these 
points  be  carefully  distinguished,  and  a group  of  air-cells,  in  the  vicinity  of  a 
bronchiole,  be  e.xamined  one  after  another  with  a microscope  of  moderate  power, 
it  will  be  found  that  each  cell  has  but  one  opening,  and  that  into  the  bronchiole, 
and  that  there  are  no  lateral  intercommunications.  This  fact  may  be  more  satis- 
factorily determined  if  a portion  of  inflated  lung  which  has  been  in  an  emphyse- 
matous condition  be  e.xamined,  in  which  air-cells  will  be  frequently  observed  so 
largely  dilated  that  their  integrity  may  be  seen  with  the  naked  eye,  as  indicated 
in  figure  298,  representing  severaj  groups  of  air-cells  drawn  the  size  of  nature  from 
a preparation  by  Dr.  Goddard. — J.  L.] 

From  recent  observations  on  the  lungs  of  man  and  mammalia,*  it 
would  appear  that,  on  tracing  one  of  the  smaller  bronchial  tubes, 
suppose  for  example  one  entering  a separate  lobule,  the  small  air-tube 
divides  and  subdivides  from  four  to  nine  times,  according  to  the  size 
of  the  lobule;  its  branches,  which  diverge  at  more  and  more  obtuse 
angles,  at  first  diminish  at  each  subdivision,  but  afterwards  continue 
stationary  in  size,  being  about  -^oth  to  ^^th  of  an  inch  in  diameter. 
Moreover,  they  gradually  lose  their  cylindrical  form,  and  appear  more 
like  irregular  passages  through  the  substance  of  the  lung,  which  are 
beset,  at  first  sparingly,  but  afterwards  closely  and  on  all  sides,  with 
numerous  little  recesses  or  dilatations,  and  ultimately  terminate  near 
the  surface  of  the  lobule  in  a group  of  similar  recesses.  These  small 
recesses  or  loculi,  whether  seated  along  the  course  or  at  the  extremity 
of  an  air-passage,  are  in  fact  the  air-cells.  They  give  the  loculated 
character  to  a section  of  the  lung,  as  seen  when  magnified  by  a mode- 
rate power,  which  reveals  a honeycomb  structure,  traversed  .by  the 
comparatively  large  air-passages.  The  cells  themselves  appear  like 
polyhedral  alveolar  cavities,  separated  from  each  other  by  thin  and 
rather  shallow  intervening  septa,  and  of  course  opening  into  the  air- 
passages.  They  do  not  open  into  one  another  by  anastomosis  or 
lateral  communication,  but  freely  communicate  through  the  medium 


: 

A B 


Three  diagrams,  to  show  the  progressive  advance  in  the  cellular  structure  of  the  lung  of  rep- 
tiles.— A.  The  upper  portion  of  the  lung  of  a serpent:  the  summit  has  cellular  walls,  the  lower 
part  forms  merely  a membranous  sac.  B.  Lung  of  the  frog,  in  which  the  cellular  structure  ex- 
tends over  the  whole  internal  surface  of  the  lung,  but  is  more  marked  at  the  upper  part.  c. 
Lung  of  the  turtle:  the  cells  here  have  extended  so  as  to  occupy  nearly  the  whole  thickness  of 
the  lung. 

of  the  common  air-passage  to  which  they  belong.  The  ultimate 
arrangement  of  the  finest  air-passages  and  air-cells  in  the  lungs  of 
mammalia  would  seem,  therefore,  closely  to  resemble,  though  on  a 

* See  Rainey,  Med.  Chir.  Transact,  vol.  xxviii.  1845.  Rossignol,  Recherches  sur  la 
Structure  intiuie  du  Poumon,  &c.,  Bruxelles,  1846. 


Fig.  299. 


THE  PULMONARY  VESSELS. 


119 


smaller  scale,  the  reticulated  structure  of  the  tortoise’s  lung,  in  which 
large  open  passages  lead  in  all  directions  to  clusters  of  wide  alveoli, 
separated  from  each  other  by  intervening  septa  of  various  depths. 

At  the  point  where  the  small  bronchial  tubes  lose  their  cylindrical 
character,  and  become  covered  on  all  sides  with  the  cells,  their 
structural  elements  also  undergo  a change.  The  muscular  fibres  dis- 
appear, the  longitudinal  elastic  bundles  are  broken  up  into  an  inter- 
lacement of  areolar  and  elastic  tissue,  which  surrounds  the  tubes  and 
forms  the  basis  of  their  walls.  The  mucous  membrane  becomes  less 
opaque,  and  ceases  to  be  provided  with  a ciliated  epithelium.  On  the 
contrary,  it  is  exceedingly  delicate,  consisting  merely  of  a thin  trans- 
parent membrane,  covered  by  a stratum  of  squamous  epithelium.  A 
similar  membrane  lines  the  air-cells,  and  by  a doubling  inwards  of 
itself,  forms  the  intervening  septa.  The  walls  of  the  cells,  their 
orifices,  and  the  margins  of  the  septa,  are  supported  and  strengthened 
by  scattered  and  coiled  elastic  fibres.  The  arrangement  of  the  capil- 
lary vessels  will  be  noticed  immediately. 

[Fig.  300.  Fig.  301. 


1 


The  relative  arrangement  of  the  air-cells  to  the  bronchioles  will  be  better  understood  by  the 
student  upon  examining  the  annexed  diagrams.  Fig.  300  represents  a transverse  section  of  a 
portion  of  parenchyma  of  the  lungs.  1.  The  orifices  of  bronchioles.  2.  The  air-cells  arranged 
around  the  bronchioles,  and  opening  into  them,  but  not  communicating  laterally.  3.  Interspaces 
filled  with  areolar  tissue,  which,  when  inflated,  is  liable  to  be  mistaken  for  the  true  air-cells. 

Fig.  301  represents  a longitudinal  section  of  a terminating  bronchiole.  1.  The  bronchiole,  in 
which  are  seen  the  orifices  (3)  of  the  air-cells  (2)  arranged  around  it  and  at  its  termination. — J.  L.] 

The  pulmonary  vessels. — These  vessels,  which  are  very  large,  and 
convey  the  blood  sent  through  the  lung  for  aeration,  have  the  following 
arrangement  within  that  organ : — 

The  branches  of  the  ptdmonary  artery  accompany  the  bronchial 
tubes,  but  they  subdivide  more  frequently,  and  are  much  smaller,  espe- 
cially in  their  remote  ramifications.  They  do  not  anastomose  in  their 
course,  and  at  length  terminate  upon  the  walls  of  the  air-cells  in  a fine 
and  dense  capillary  network,  from  which  the  radicles  of  the  pulmonary 
veins  arise.  The  smaller  branches  of  these  veins,  especially  near  the 


120 


THE  BRONCHIAL  VESSELS. 


surface  of  the  lung,  frequently  do  not  accompany  the  bronchia  and 
arterial  branches  (Dr.  T.  Addison,  Bourgery),  but  are  found  to  run 
alone  for  a short  distance  through  the  substance  of  the  organ,  and  then 
to  join  some  deeper  vein  which  does  run  by  the  side  of  a bronchial 
tube,  uniting  together,  and  also  forming,  according  to  Rossignol,  fre- 
quent lateral  communications.  The  veins  coalesce  into  large  branches, 
which  at  length  accompany  the  arteries,  and  thus  proceed  to  the  root 
of  the  lung.  In  their  course  through  the  lung,  the  artery  is  usually 
found  above  and  in  front  of  a bronchial  tube,  and  the  vein  below. 

The  pulmonary  vessels  are  peculiar,  inasmuch  as  the  artery  conveys 
dark  blood,  whilst  the  veins  carry  red  blood.  The  pulmonary  veins, 
unlike  the  other  veins  of  the  body,  are  not  more  capacious  than  their 
corresponding  arteries;  indeed,  according  to  Winslow,  Santorini, 
Haller,  and  others,  they  are  somewhat  less  so.  These  veins  have  no 
valves.  Lastly,  it  may  be  remarked,  that  whilst  the  arteries  of  different 
lobules  are  independent,  their  veins  freely  anastomose  together. 

The  capillary  network  of  the  pulmonary  vessels  is  spread  beneath 
the  thin  transparent  mucous  membrane  of  both  the  terminal  and  lateral 
air-cells,  and  is  found  wherever  the  finest  air-tubes  have  lost  their 
cylindrical  character,  and  become  beset  with  cells.  Around  the  bottom 
of  each  cell  there  is  an  arterial  circle,  which  communicates  freely  with 
similar  neighbouring  circles,  the  capillary  system  of  ten  or  twelve 
cells  being  thus  connected  together,  as  may  be  seen  upon  the  surface 
of  the  lung.  From  these  circular  vessels,  which  vary  in  diameter 
from  TsVu  to  VTg  inch,  the  capillary  network  arises,  covering  the 
bottom  of  each  cell,  ascending  also  between  the  duplicature  of  mucous 
membrane  in  the  intercellular  septa,  and  surrounding  the  openings  of 

the  cells.  According  to  Mr.  Rainey, 
the  capillary  network,  where  it  rises 
into  the  intercellular  partitions,  forms 
a double  layer  in  the  lungs  of  reptiles, 
but  is  single  in  the  lungs  of  man  and 
mammalia. 

The  capillaries  themselves  are  very 
fine,  the  smallest  measuring,  in  injected 
specimens,  from  o to  soVffth  inch ; 
the  network  is  so  close  that  the  meshes 
are  scarcely  wider  than  the  vessels 
themselves.  The  coats  of  the  capil- 
laries are  also  exceedingly  thin,  and 
air-cells  to  aVonchiole,7ndtife'd^^^^^^  more  readily  allow  of  the  free 

of  the  capillaries  t.  A bronchiole ; at  Us  gjjhalation  and  absorption  of  which 

bottom  IS  seen  the  orifices  oi  two  smaller  , , n * i tt-  •! 

bronchioles,  and  upon  ils  surface  a capillary  the  pulmonary  Cells  are  the  Seat.  Iveil 
rete  communicating  with  that  (3)  of  the  air-  Hales  estimated  the  entire  extent 
cells  (2).  f rom  a preparation  by  Topping.  » , . ^ , 

_j.  L.]  j r D inner  surface  of  the  air-tubes 

and  pulmonary  cells  at  more  than 
21,000  square  inches;  but  no  great  reliance  can  be  placed  on  such 
calculations. 

The  bronchial  vessels. — The  bronchial  arteries  and  veins,  which  are 
much  smaller  than  the  pulmonary  vessels,  carry  blood  for  the  nutrition 


[Fig.  302. 


Represents  the  relative  arrangement  of 


THE  BRONCHIAL  VESSELS. 


121 


of  the  lung,  and  are  doubtless,  also,  the  principal  source  of  the  mucous 
secretion  found  in  the  interior  of  the  air-tubes,  and  of  the  thin  albu- 
minous fluid  which  moistens  the  pleura  pulmonalis. 

The  bronchial  arteries,  from  one  to  three  in  number  for  each  lung, 
arise  from  the  aorta,  or  from  an  intercostal  artery,  and  follow  the 
divisions  of  the  air-tubes  through  the  lung.  They  are  ultimately  dis- 
tributed in  three  ways:  many  of  their  branches  ramify  in  the  bronchial 
lymphatic  glands,  the  coats  of  the  large  blood-vessels,  and  on  the  walls 
of  the  large  and  small  air-tubes,  as  far  as  these  retain  their  cylindrical 
form  and  their  opaque  ciliated  mucous  membrane;  others  form  plexuses 
in  the  interlobular  cellular  tissue;  and  lastly,  branches  spread  out  upon 
the  surface  of  the  lung  beneath  the  pleura. 

The  superficial  set,  or  subpleural  arteries,  form  plexuses  and  a ca- 
pillary network,  which  may  be  distinguished  from  those  of  the  pul- 
monary vessels  of  the  superficial  air-cells  by  their  tortuous  course  and 
open  arrangement,  and  also  by  their  being  outside  the  investing  mem- 
brane of  the  lobules,  and  by  ultimately  ending  in  the  branches  of  the 
superficial  set  of  bronchial  veins.  Of  the  deeper  seated  arteries,  those 
which  supply  the  bronchial  lymphatic  glands,  and  those  which  pene- 
trate a certain  distance  upon  the  air-tubes  and  large  vessels,  end  in 
corresponding  deep  bronchial  veins ; the  interlobular  arterial  plexuses 
send  venous  radicles,  which  end  either  in  the  superficial  or  the  deep 
set  of  bronchial  veins,  and  serve  to  connect  them  together;  lastly,  the 
capillary  network  of  the  innermost  branches  of  the  bronchial  arteries, 
which  is  found  upon  the  finest  cylindrical  air-tubes,  communicates 
with  the  system  of  pulmonary  vessels,  so  that  its  blood  returns  by  the 
pulmonary  veins.  The  exact  nature  of  this  last-named  communication 
is  difficult  to  determine,  inasmuch  as  experiments  by  injection,  espe- 
cially of  so  delicate  a capillary  system  as  that  of  the  lung,  are  liable 
either  to  be  defective  or  to  be  rendered  inaccurate  by  rupture  and  ex- 
travasation. According  to  Ruysch,  Haller,  Soemmerring,  and  Reis- 
seissen,  the  terminations  of  the  deep  bronchial  arteries  anastomose 
with  those  of  the  pulmonary  arteries,  or,  at  any  rate,  the  capillary 
networks  of  the  two  sets  of  vessels  anastomose.  Rossignol  denies 
even  the  latter  mode  of  communication,  because  he  could  not  succeed 
in  injecting  from  the  pulmonary  artery  the  vessels  of  the  cylindrical 
air-tubes,  which  are  destitute  of  air-cells:  he  believes  that  the  only 
communication  between  the  bronchial  and  pulmonary  vessels  is  by 
means  of  some  minute  bronchial  venous  radicles  which  end  in  the  pul- 
monary veins. 

It  was  found  by  Rossignol,  first,  that  injections  by  the  bronchial  arteries  re- 
turned by  both  the  pulmonary  and  bronchial  veins,  but  not  by  the  pulmonary 
artery;  secondly,  that  injections  by  the  prdmonary  arteries  returned  entirely  by 
the  pulmonary  veins,  but  not  by  the  bronchial  arteries ; and  thirdly,  that  by  in- 
jecting the  pulmonary  veins,  it  was  easy  to  fill  all  the  other  vessels,  viz.,  the  pul- 
monary artery  and  the  bronchial  arteries  and  veins. 

The  bronchial  veins,  therefore,  have  not  quite  so  large  a distribution 
in  the  lung  as  the  bronchial  arteries.  The  superficial  and  deep  veins 
unite  at  the  root  of  the  lung,  and  on  the  right  side  open  into  the  vena 
azygos,  on  the  left  usually  into  the  superior  intercostal  vein. 

VOL,  II.  11 


122 


DEVELOPMENT  OF  THE  LUNGS. 


The  absorbent  vessels. — The  lungs  are  well  supplied  with  lymphatic 
vessels  and  glands.  The  lymphatics  consist  of  a superficial  and  a deep 
set.  The  former  constitute  a network  on  the  surface  of  the  lung,  and 
being  joined  by  the  interlobular  lymphatics  of  the  deep  set,  which  tra- 
verse the  interlobular  cellular  tissue,  run  towards  the  root  of  the  lung. 
Here,  together  with  the  deep  absorbents,  they  pass  through  the  bron- 
chial lymphatic  glands  found  in  that  situation.  These  glands,  which 
are  numerous  and  of  considerable  size,  lie,  some  within  the  lung  around 
the  largest  bronchia,  and  some  near  the  bifurcation  of  the  trachea 
and  around  the  bronchi.  They  have  a great  tendency  to  induration, 
and  usually  contain  much  of  the  peculiar  carbonaceous  colouring 
matter  already  mentioned  as  existing  in  the  lung,  and  which  is  also 
found  in  abundance  along  the  course  of  the  lymphatic  vessels. 

JVerves. — The  lungs  are  supplied  by  nerves  from  the  anterior  and 
posterior  pulmonary  plexuses.  These  are  formed  chiefly  by  branches 
from  the  pneumogastric  nerves,  joined  by  others  from  the  sympathetic 
system.  The  fine  nervous  cords  enter  at  the  root  of  the  lung,  and 
follow  the  air-tubes.  Their  final  distribution  requires  further  exami- 
nation. According  to  Remak,  whitish  filaments  (from  the  par  vagum) 
follow  the  bronchia  as  far  nearly  as  the  surface  of  the  lung.  Grayish 
filaments  proceeding  from  the  sympathetic,  and  having  very  minute 
ganglia  upon  them  in  their  course,  have  also  been  traced  by  the  last- 
mentioned  anatomist  to  the  bronchia  and  pleura. 


DEVELOPMENT  OF  THE  LUNGS  AND  TRACHEA. 

The  lungs  first  appear  as  two  little  protrusions  upon  the  front  of  the  cesophageal 
portion  of  the  alimentary  canal,  completely  hid  by  the  rudimentary  heart  and  liver. 
These  primitive  protrusions  or  tubercles  are  visible  in  the  chick  on  the  third  day 
of  incubation  (see  fig.  303  for  their  appearance  on  the  fourth  day.)  According  to 
Baer  and  others,  they  are,  from  the  first,  hollow,  their  internal  cavities  communi- 
cating with  the  oesophagus  and  being 


Fig.  303. 


lined  by  a prolongation  of  its  inner  layer. 
At  a later  period  they  are  connected  with 
the  oesophagus  by  means  of  a long  pe- 
dicle, which  ultimately  forms  the  trachea, 
whilst  the  bronchia  and  air-cells  are  de- 
veloped by  the  successive  ramification 
of  the  internal  cavity  to  form  caecal  tubes, 
after  the  manner  of  the  ducts  of  glands. 
Reichert  and  Bischoff,  on  the  other  hand, 
are  of  opinion  that  the  rudiments  of  the 
lungs  are  at  first  solid,  and  are  produced 
by  a thickening  or  protrasion  of  the  outer 
layers  only  of  the  cesophageal  tube.  The 
inner  layer  never  enters  them,  but  they 
Fig.  303  illustrates  the  development  of  the  ggou  become  connected  with  the  com- 
respi'ralory  orpns,— (Ralhke.)— A.  ®sop  agus  trachea,  which  appears  like  a 

of  a chick  on  the  fourth  day  of  incubation,  with  . & ’ , up  , , ^ 

the  rudimentary  lung  of  iheleft  side,  seen  late-  white  streak  along  the  whole  length  oi 
rally.  1.  The  front,  and  2.  The  back  of  the  ceso-  the  oesophagus.  The  rudimentary  lungs, 
phagus.  3.  Rudimentary  lung  protruding  from  which  are  at  first  Smooth  and  undivided, 
that  tube.  4.  Stomach,  b.  The  same  seen  in  consist  of  two  masses  of  blastema  COm- 
front,  so  as  to  show  boih  lun^^^  and  ^heir  Sub- 

respiratory  organs  oi  embryo  ot  the  horse.  1.  i i • j_  r 

Tongue.  2.  Larynx.  3.  Trachea.  4.  Lungs  Stance,  the  bronchi  soon  begin  to  form 
seen  from  behind.  as  solid  white  tracts,  which  join  the 

trachea,  and  the  future  cavity  in  their 
interior  first  appears  as  a deeper  coloured  line.  The  ultimate  bronchial  ramifica- 


THE  LARYNX.  123 

tions,  and  probably  the  air-cells  too,  are  formed  by  the  successive  budding  out 
and  subsequent  excavation  of  the  earlier  developed  bronchial  tubes. 

As  to  the  trachea  itself,  its  precise  mode  of  origin  and  formation  is  undetermined. 
Baer  regards  it  as  a tubular  prolongation  from  the  (Esophagus,  but  this  is  doubtful, 
and  others  believe  it  to  be  formed  upon  the  (Esophagus,  and  afterwards  to  open 
into  that  canal.  According  to  Fleischmann,  the  rings  of  the  trachea  are  seen  at 
the  fourth  week  in  the  human  embryo,  formed  of  lateral  halves  which  afterwards 
unite.  Rathke  and  Valentin  state,  on  the  contrary,  that  they  arise  by  simple 
strips  of  cartilage.  They  appear  to  increase  in  number  during  development.  The 
vibratile  cilia  have  been  seen  very  early. 

For  a long  time  the  lungs  are  very  small,  and  occupy  only  a little  space  at  the 
back  part  of  the  chest.  In  an  embryo  16  lines  in  length,  their  proportionate 
weight  to  the  body  was  found  by  Meckel  to  be  1 to  25;  in  another,  29  lines  long, 
it  was  1 to  27 ; at  4 inches  in  length  1 to  41,  and  at  the  full  period  1 to  70. 
Huschke  found  that  the  lungs  of  stdl-born  male  children  were  heavier  in  propor- 
tion to  the  weight  of  the  body  than  those  of  female  children ; the  ratio  being, 
amongst  females,  1 to  76,  and  in  males  1 to  55. 

Changes  after  birth. — No  organ  undergoes  such  rapid  and  remarkable  changes 
after  birth,  as  those  which,  in  consequence  of  the  commencement  of  respiration, 
affect  the  lungs  in  almost  every  respect,  viz.,  in  size,  position,  form,  consistence, 
texture,  colour,  and  weight.  An  accurate  knowledge  of  these  changes  furnishes 
the  only  means  of  distinguishing  between  a still-born  child  and  one  that  has  re- 
spired.* 

Position,  size,  and  form. — In  a fcetus  at  the  full  period  or  in  a still-bom  child,  the 
lungs,  comparatively  small,  lie  packed  at  the  ba(3k  of  the  thorax,  and  do  not 
entirely  cover  the  sides  of  the  pericardium  ; subsequently  to  respiration,  they  ex- 
pand and  completely  cover  the  pleural  portions  of  that  sac,  and  are  also  in  con- 
tact with  every  part  of  the  thoracic  parietes,  which  is  covered  with  the  pleural 
membrane.  At  the  same  time,  their  previously  thin  sharp  margins  become  more 
obtuse,  and  their  whole  form  is  less  compressed. 

Consistence,  texture,  and  colour. — The  introduction  of  air,  and  of  an  increased 
quantity  of  blood  into  the  compact,  heavy,  granular,  yellowish-pink,  gland-like 
substance  of  the  fcetal  lungs,  which  ensues  immediately  upon  birth,  converts  their 
tissue  into  a loose,  light,  rose  pink,  spongy  structure,  which,  as  already  mentioned, 
floats  in  water.  The  changes  thus  simultaneously  produced  in  their  consistence, 
colour,  and  texture,  occur  first  at  their  anterior  borders,  and  proceed  backwards 
through  the  lungs  : they,  moreover,  appear  in  the  right  lung  a little  in  advance  of 
the  left. 

Weight. — The  absolute  weight  of  the  lungs,  having  gradually  increased  from  the 
earliest  period  of  development  to  birth,  undergoes  at  that  time  from  the  blood  then 
poured  into  them,  a very  marked  addition,  amounting  to  more  than  one-third  of  their 
previous  weight : for  example,  the  lungs  before  birth  weigh  about  one  and  a half 
ounce,  but,  after  complete  expansion  by  respiration,  they  weigh  as  much  as  two 
and  a half  ounces.  The  relative  weight  of  the  lungs  to  the  body,  which,  at  the 
termination  of  intra-uterine  life  is  about  1 to  70,  becomes,  after  respiration,  on  an 
average  about  1 to  35  or  40,  a proportion  which  is  not  materially  altered  through 
life.  Their  specific  gravity  is  at  the  same  time  changed  from  1-056  to  about  -342. 

Changes  in  the  trachea  after  birth. — In  the  fcetus,  the  trachea  is  flattened  before 
and  behind,  its  anterior  surface  being  even  somewhat  depressed;  the  end  of  the 
cartilages  touch;  and  the  sides  of  the  tube,  which  now  contains  only  mucus,  are 
applied  to  one  another.  The  effect  of  respiration  is  at  first  to  render  the  trachea 
open,  but  stfll  flattened  in  front ; afterwards  it  becomes  convex. 

THE  LARYNX,  OR  ORGAN  OF  VOICE. 

The  upper  part  of  the  air-passage  is  modified  in  its  structure  to  form 
the  organ  of  voice.  This  organ,  nam,ed  the  larynx,  [Xapuvto,  to  cry,]  is 

* It  must  be  remembered  that  these  changes  may  present  themselves,  in  different  cases, 
in  every  possible  degree  of  variety,  owing  to  the  amount  of  respiration  which  has  taken 
place,  in  either  or  both  lungs.  For  particular  details  on  these  points,  and  also  for  an  ex- 
planation of  certain  sources  of  fallacy,  see  the  proper  treatises  on  medical  jurisprudence. 


124 


THYROID  CARTILAGE. 


placed  at  the  upper  and  fore  part  of  the  neck,  where  it  forms  a con-, 
siderable  prominence  in  the  middle  line.  It  lies  between  the  large 
vessels  of  the  neck,  and  below  the  tongue  and  os  hyoides,  to  which 
bone  it  is  suspended.  It  is  covered  in  front  by  the  cervical  fascia 
along  the  middle  line,  and  on  each  side  by  the  sterno-hyoid,  sterno- 
thyroid, and  thyro-hyoid  muscles,  by  the  upper  end  of  the  thyroid 
body,  and  by  a small  part  of  the  inferior  constrictor  of  the  pharynx. 
Behind,  it  is  covered  by  the  pharyngeal  mucous  membrane,  and  forms 
the  anterior  boundary  of  the  lower  part  of  the  pharynx,  into  which 
cavity  it  opens  above,  whilst  below  it  leads  into  the  windpipe. 

The  larynx  is  cylindrical  at  the  lower  part,  where  it  joins  the 
trachea,  but  it  widens  above,  becomes  flattened  behind  and  at  the 
sides,  and  presents  a blunted  vertical  ridge  in  front. 

The  larynx  consists  of  a framework  of  cartilages,  articulated  to- 
gether and  connected  by  proper  ligaments,  two  of  which,  named  the 
true  vocal  cords,  are  immediately  concerned  in  the  production  of  the 
voice.  It  also  possesses  muscles,  which  move  the  cartilages  one  upon 
another,  a mucous  membrane  lining  its  internal  surface,  numerous 
mucous  glands,  and  lastly,  blood-vessels,  lymphatics,  and  nerves, 
besides  cellular  tissue  and  fat. 

Cartilages  of  the  Larxjnx. 

The  cartilages  of  the  larynx  consist  of  three 
single  and  symmetrical  pieces,  named  respec- 
tively the  thyroid  cax'lilage,  the  cricoid  cax'ti- 
lage,  and  the  cartilage  of  the  epiglottis,  and 
of  six  others,  which  occur  in  pairs,  namely, 
the  two  arytenoid  cartilages,  the  cornicula 
laryngis,  and  the  cuneiform  cartilages.  In 
all,  there  are  nine  distinct  pieces,  the  two  cor- 
nicula and  two  cuneiform  cartilages  being 
very  small.  Of  these,  only  the  thyroid  and 
cricoid  cartilages  are  seen  on  the  front  and 
sides  of  the  larynx  (see  fig.  304);  the  aryte- 
noid cartilages,  surmounted  by  the  cornicula 
laryngis,  together  with  the  back  of  the  cricoid 
cartilage,  on  which  they  rest,  form  the  poste- 
rior wall  of  the  larynx,  whilst  the  epiglottis 
is  situated  in  front,  and  the  cuneiform  carti- 
lages on  each  side  of  the  upper  opening. 

The  thyroid  cartilage  (cartilago  thyreoidea, 
v.  scLitiformis  ; a shield,  and  £k5os,)  is  the 

ridge,  or  pomum  Adami.  2.  largest  of  the  pieces  Composing  the  larynx. 

It  is  formed  by  two  flat  lamellte,  united  in 
5,  6.  Cricoid  cartilage.  7.  Right  front,  at  an  acute  angle  along  the  middle  line, 
arytenoid  cartilage.  where  they  form  a vertical  projection  (fig. 

304,^),  which  becomes  gradually  efl’aced,  as  it  is  traced  from  above 
downwards.  The  two  lamellae,  diverging  one  from  the  other 
backwards,  embrace  the  cricoid  cartilage,  and  terminate  posteriorly 
by  two  thick  projecting  vertical  borders,  separated  widely  from  each 


Fig.  304. 


Cartilages  of  the  larynx  sepa- 
rated and  seen  in  front.  1 lo  4. 
Thvroid  cartilaere.  1.  Verrical 


CRICOID  CARTILAGE. 


125 


other;  hence,  the  thyroid  cartilage  is  altogether  wanting  behind.  The 
angular  projection  on  the  anterior  surface  in  the  median  line  is  subcu- 
taneous, and  is  much  more  prominent  in  the  male  than  in  the  female, 
being  named  in  the  former  the  pomum  Adami.  The  lateral  haloes  (2), 
or  lamellae,  named  the  alee,  are  somewhat  quadrilateral  in  form,  and 
are  perfectly  symmetrical.  The  external  flattened  surface  of  each  ala 
is  marked  by  an  indistinct  oblique  line,  which,  commencing  at  a tu- 
bercle situated  at  the  back  part  of  the  upper  border  of  the  cartilage, 
passes  downwards  and  forwards,  so  as  to  mark  off  the  anterior  three- 
fourths  of  the  surface  from  the  remaining  posterior  portion.  This  line 
gives  attachment  below  to  the  sterno-thyroid,  and  above  to  the  thyro- 
hyoid muscle,  whilst  the  small  smooth  surface  behind  it  gives  origin  to 
part  of  the  inferior  constrictor  of  the  pharynx,  and  affords  attach- 
ment, by  means  of  cellular  tissue,  to  the  thyroid  body.  On  their  inter- 
nal or  posterior  surfaces,  the  two  aim  are  smooth,  and  slightly  concave, 
and  by  their  union  in  front,  form  a retreating  angle  within  correspond- 
ing with  the  ridge  on  the  anterior  aspect  of  the  cartilage.  The  greater 
portion  of  the  internal  surface  of  the  thyroid  cartilage  is  connected  to 
other  parts,  but  the  upper  and  posterior  portion  of  each  ala  is  lined 
loosely  by  the  mucous  membrane  of  the  pharynx  only,  and  forms  the 
outer  boundary  of  a lateral  groove  seen  on  each  side  at  the  back  of 
the  larynx.  The  upper  border  of  the  thyroid  cartilage  is  slightly  con- 
cave at  the  sides,  and  deeply  notched  in  the  middle  line,  above  the 
pomum  Adami  (1).  This  border  is  connected,  in  its  whole  extent,  to 
the  os-hyoides  by  a strong  membrane,  named  the  thyro-hyoid.  The 
lower  border,  which  is  shorter  than  the  upper,  is  scolloped  out  into 
three  shallow  concavities,  a wider  one  in  the  middle  and  a smaller  one 
at  each  side,  separated  from  the  first  by  an  intervening  tubercle.  This 
border  is  connected  with  the  cricoid  cartilage,  in  the  median  line  by 
the  crico-thyroid  membrane,  and  on  each  side  by  the  crico-thy- 
roid  muscle.  The  posterior  borders  of  the  thyroid  cartilage,  which 
are  rather  thick  and  rounded,  have  a vertical  direction,  and  are 
prolonged  upwards  and  downwards,  into  two  processes,  named 
cornua,  which  form  respectively  the  posterior  limits  of  the  shallow 
lateral  notches  seen  on  the  upper  and  lower  margins  of  the  cartilage. 
The  stylo-pharyngeus  and  palato-pharyngeus  muscles  of  each  side  are 
attached  to  these  posterior  borders.  Of  the  four  cornua,  all  of  which 
bend  inwards,  the  tw6  superior,  or  great  cornua  (3),  pass  backwards, 
upwards,  and  inwards,  and  terminate  each  by  a blunt  extremity,  which 
is  connected,  by  means  of  the  lateral  thyro-hyoid  ligament,  to  the  tip 
of  the  corresponding  great  cornu  of  the  os  hyoides.  The  inferior,  or 
smaller,  cornua  (4),  which  are  somewhat  thicker  but  shorter,  are  di- 
rected forwards  and  inwards,  and  present  each,  on  the  inner  aspect 
of  the  tip,  a smooth  surface,  for  articulation  with  a prominence  on  the 
side  of  the  cricoid  cartilage. 

The  cricoid  cartilage,  so  named  from  its  being  shaped  like  a ring 
(x^ixos,  a ring;  siSos,)  is  thicker  in  substance  and  stronger  than  the  thy- 
roid cartilage;  it  forms  the  inferior,  and  a considerable  portion  of  the 
back  part  of  the  larynx,  and  is  the  only  one  of  the  cartilages  which 
completely  surrounds  this  organ.  It  is  deeper  behind  (®),  where  the 

11* 


126 


ARYTENOID  CARTILAGES. 


thyroid  cartilage  is  deficient,  measuring  in  the  male  about  an  inch 
from  above  downwards,  but  is  much  narrower  in  front  (®),  where  its 
vertical  measurement  is  only  two  lines  and  a half.  The  cricoid  car- 
tilage is  circular  beloio,  but  higher  up  it  is  somewhat  compressed  late- 
rally, so  that  the  passage  through  it  is  elliptical,  its  antero-posterior 
diameter  being  longer  than  the  transverse.  The  external  surface  is 
convex  and  smooth  in  front  and  at  the  sides,  where  it  affords  attach- 
ment to  the  crico-thyroid  muscles,  and  behind  these  to  the  inferior 
constrictor  muscle  on  each  side.  The  surface  posteriorly  is  three  or 
four  times  deeper  and  somewhat  broader.  It  presents  in  the  middle 
line  a slight  vertical  ridge,  to  which  some  of  the  longitudinal  fibres  of 
the  oesophagus  are  attached.  On  each  side  of  this  ridge  is  a broad 
depression  for  the  posterior  crico-arytenoid  muscle,  and  externally  and 
anteriorly  to  that  a small  rounded  and  slightly  raised  surface  for  arti- 
culation on  either  side  with  the  inferior  cornu  of  the  thyroid  cartilage. 
The  internal  surface  of  the  cricoid  cartilage  is  smooth,  and  is  lined 
by  the  laryngeal  mucous  membrane.  The  lower  border  is  rounded 
and  horizontal,  and  is  connected  by  a membrane  to  the  first  ring  of 
the  trachea.  The  upper  border  which,  owing  to  the  greater  depth  of 
the  cartilage  behind,  is  inclined  obliquely  upwards  and  backwards,  is 
connected,  in  front,  to  the  thyroid  cartilage  by  the  crico-thyroid  mem- 
brane. On  each  side  it  gives  attachment  to  the  lateral  part  of  the 
crico-thyroid  membrane,  and  to  the  lateral  crico-arytenoid  muscle. 
Posteriorly  this  border  of  the  cartilage  presents  a slight  notch  in  the 
middle  line,  which  gives  origin  to  some  of  the  fibres  of  the  arytenoid 
muscle.  On  the  sides  of  this  notch,  and  consequently  on  the  highest 
part  of  the  cartilage,  are  two  convex  oval  articular  facets,  directed  up- 
wards and  outwards,  to  which  the  arytenoid  cartilages  are  articulated. 

The  arytenoid  cartilages,  (cartilagines  arytasnoidese,  v.  pyramidales, 
fig.  304,^;  a^uTaiva,  a kind  of  ewer,  sihg,)  are  two  in  number,  and  are 
perfectly  symmetrical  in  form.  They  may  be  compared  to  two  three- 
sided  pyramids  recurved  at  the  summit,  measuring  from  five  to  six 
lines  in  height,  resting  by  their  bases  on  the  posterior  and  highest  part 
of  the  cricoid  cartilage,  and  approaching  near  to  one  another  towards 
the  median  line.  Each  measures  upwards  of  three  lines  in  width,  and 
more  than  a line  from  before  backwards.  Of  its  three  faces,  the  pos- 
terior is  broad,  triangular,  and  excavated  from  above  downwards,  so 
that  the  summit  of  the  cartilage  is  curved  backwards.  This  concave 
smooth  surface  lodges  part  of  the  arytenoid  muscle.  The  anterior 
surface,  convex  in  its  general  outline,  and  somewhat  rough,  gives 
attachment  to  the  thyro-arytenoid  muscle,  and,  by  a small  tubercle,  to 
the  corresponding  superior  or  false  vocal  cord.  The  internal  surface, 
which  is  the  narrowest  of  the  three,  and  somewhat  flattened,  is 
parallel  with  and  very  near  to  that  of  the  opposite  cartilage,  being 
covered  by  the  laryngeal  mucous  membrane.  The  anterior  and  pos- 
terior borders,  which  limit  the  internal  face,  ascend  nearly  in  the  same 
vertical  plane,  whilst  the  external  border,  which  separates  the  anterior 
from  the  posterior  surface,  is  directed  obliquely  upwards  and  inwards. 

The  base  of  each  arytenoid  cartilage  is  slightly  hollowed,  having 
towards  its  inner  part  a smooth  surface  for  articulation  with  the  cri- 


EPIGLOTTIS. 


127 


coid  cartilage.  Two  of  its  angles  are  remarkably  prominent,  viz., 
one  external,  short,  and  rounded,  which  projects  backwards  and  out- 
wards, and  into  which  the  posterior  and  the  lateral  crico-arytenoid 
muscles  are  inserted;  the  other  anterior,  which  is  more  pointed,  and 
forms  a horizontal  projection  forwards,  to  which  the  corresponding 
true  vocal  cord  is  attached. 

The  apex  of  each  arytenoid  cartilage  curves  backwards  and  a little 
inwards,  and  terminates  in  a rounded  point,  which  is  surmounted  by’' 
a small  cartilaginous  appendage  named  corniculum  laryngis,  to  be 
next  described. 

The  cornicula  laryngis,  or  cartilages  of  Santorini,  (capitula  Santo- 
rini,) are  two  small  yellowish  cartilaginous  nodules  of  a somewhat 
triangular  or  conical  shape;  which  are  articulated  with  the  summits  of 
the  arytenoid  cartilages,  and  serve  as  it  were  to  prolong  them  back- 
wards and  inwards.  They  are  sometimes  united  to  the  arytenoid 
cartilages. 

The  cuneiform  cartilages,  or  cartilages  of  Wrisherg,  are  two  very 
small  soft  ymllowish  cartilaginous  bodies,  placed  one  on  each  side  of 
the  larynx  in  the  fold  of  mucous  membrane  which  extends  from  the 
summit  of  the  arytenoid  cartilage  to  the  epiglottis.  They  have  a 
conical  form,  their  base  or  broader  part  being  directed  upwards.  They 
occasion  small  conical  elevations  of  the  mucous  membrane  within  the 
larynx,  a little  in  advance  of  the  cartilages  of  Santorini,  with  which, 
however,  they  are  not  directly  connected. 

The  epiglottis,  (smyXuT'ng  ; fig.  308,  e,)  is  a single  median  part  formed 
by  a thin  lamella  of  yellow  cartilage,  shaped  somewhat  like  a cordate 
leaf,  and  covered  by  mucous  membrane.  It  is  placed  in  front  of  the 
superior  opening  of  the  larynx  projecting  upwards  immediately  behind 
the  base  of  the  tongue.  In  the  ordinary  condition  its  direction  is  ver- 
tical, the  free  extremity  curving  forward  towards  the  tongue,  but 
during  the  act  of  swallowing  it  is  carried  downwards  and  backwards 
over  the  entrance  into  the  larynx,  which  it  covers  and  protects. 

The  cartilage  of  the  epiglottis  is  broad  and  somewhat  rounded  at 
its  upper  free  margin,  but  inferiorly  becomes  pointed,  and  is  prolonged 
by  means  of  a long,  narrow,  fibrous  band  (the  thyro-epiglottic  liga- 
ment) to  the  deep  angular  depression  between  the  alae  of  the  thyroid 
cartilage,  to  which  it  is  attached,  behind  and  below'  the  median  notch. 
Its  lateral  borders,  which  are  convex,  are  only  partly  free,  being  in 
part  concealed  within  the  folds  of  mucous  membrane  which  pass  back 
on  each  side  to  the  arytenoid  cartilages.  The  anterior  or  lingual  sur- 
face is  free  only  in  the  upper  part  of  its  extent,  where  it  is  covered  by 
mucous  membrane.  Lower  down,  the  membrane  is  reflected  from  it 
forwards  to  the  base  of  the  tongue,  forming  one  median  fold  and  two 
lEfteral  folds  or  frgenula,  sometimes  called  the  glosso-epiglottidean  liga- 
ments. The  adherent  portion  of  this  surface  is  also  connected  with 
the  posterior  surface  of  the  os  hyoides  by  means  of  a median  elastic 
tissue  named  the  hyo-epiglottic  ligament,  and  is  moreover  in  contact 
with  some  glands  and  fatty  tissue.  The  posterior  or  laryngeal  sur- 
face of  the  epiglottis,  which  is  free  in  the  whole  of  its  extent,  is  con- 
vex from  above  downwards,  but  concave  from  side  to  side.  It  is 


128 


LIGAMENTS  OF  THE  LARYNX. 


closely  covered  by  the  mucous  membrane,  on  removing  which,  the 
yellow  cartilaginous  lamella  of  which  the  epiglottis  consists  is  seen  to 
be  pierced  by  numerous  little  pits  and  perforations,  in  wdiich  are 
lodged  small  glands  which  open  on  the  surface  of  the  mucous  mem- 
brane. 

Structure  of  the  cartilages  of  the  larynx. — The  epiglottis,  together 
with  the  cornicula  laryngis  and  cuneiform  cartilages,  are  composed  of 
what  is  called  yellow  or  spongy  cartilage,  which  has  little  tendency 
to  ossify.  The  structure  of  all  the  other  cartilages  of  the  larynx  re- 
sembles that  of  the  costal  cartilages,  like  which,  they  are  very  prone 
to  ossification  as  life  advances. 

Ligaments  of  the  larynx. — The  ligaments  of  the  larynx  zxe  extrinsic, 
or  those  which  connect  it  with  contiguous  parts,  as  the  os  hyoides  and 
the  trachea,  and  intrinsic,  by  means  of  which  its  several  cartilaginous 
pieces  are  connected  one  to  the  other. 

Extrinsic  ligaments. — The  larynx  is  connected  with  the  os  hyoides 
by  a broad  membrane  and  by  two  round  lateral  ligaments.  The  thyro- 
hyoid membrane,  or  middle  thyro-hyoid  ligament,  is  a broad,  fibrous, 
and  somewhat  elastic  membrane,  which  passes  up  from  the  whole 
length  of  the  superior  border  of  the  thyroid  cartilage  to  the  os  hyoides, 
being  attached  not  to  the  inferior  part  of  that  bone,  but  along  the 
highest  part  of  its  internal  or  posterior  surface.  Owing  to  this  ar- 
rangement, the  top  of  the  larynx,  when  drawn  upwards,  is  permitted 
to  slip  within  the  circumference  of  the  hyoid  bone,  between  which  and 
the  upper  part  of  the  thyroid  cartilage,  there  is  occasionally  found  a 
small  synovial  bursa.  The  thyro-hyoid  membrane  is  thick  and  sub- 
cutaneous towards  the  middle  line,  but  on  each  side  becomes  thin  and 
loose,  and  is  covered  by  the  thyro-hyoid  muscles.  Behind  it  is  the 
epiglottis  with  the  mucous  membrane  of  the  base  of  the  tongue,  sepa- 
rated however  by  much  adipose  tissue  and  some  glands.  It  is  perfo- 
rated by  the  superior  laryngeal  artery  and  nerve  of  each  side. 

At  the  posterior  limits  of  the  thyro-hyoid  membrane  are  found  the 
right  and  left  lateral  thyro-hyoid  ligaments,  rounded  yellowish  cords, 
which  pass  up  from  the  superior  cornua  of  the  thyroid  cartilage,  to 
the  rounded  extremities  of  the  great  cornua  of  the  hyoid  bone.  These 
lateral  thyro-hyoid  ligaments  are  distinctly  elastic,  and  frequently  en- 
close a small  oblong  cartilaginous  nodule,  which  has  been  named  car- 
tilaso  triticea:  sometimes  this  nodule  is  bony. 

The  membrane  which  connects  the  lower  border  of  the  larynx  (cri- 
coid cartilage)  to  the  first  ring  of  the  trachea,  forms  the  commencement 
of  that  tube. 

Intrinsic  ligaments. — The  thyroid  and  cricoid  cartilages  are  con- 
nected together  in  front  and  at  each  side.  In  the  former  direction, 
a strong  triangular  yellowish  ligament,  consisting  chiefly  of  elastic 
tissue,  is  attached  to  the  contiguous  borders  of  these  two  cartilages. 
It  is  named  the  crico-thyroid  membrane,  and  sometimes  the  jiyramidal 
or  conoid  ligament  (fig.  306).  Its  base  is  turned  downwards,  and 
is  fixed  to  the  upper  margin  of  the  cricoid  cartilage.  Its  anterior  sur- 
face is  convex  and  is  covered  at  the  sides  by  the  crico-thyroid  mus- 
cles, and  crossed  horizontally  by  a small  anastomotic  arterial  arch, 
formed  by  the  junction  of  the  crico-thyroid  branches  of  the  right  and 


INTERIOR  OF  THE  LARYNX. 


129 


left  superior  thyroid  arteries.  The  posterior  surface  of  this  membrane 
is  covered  only  by  the  mucous  membrane  of  the  larynx. 

On  tracing  the  crico-thyroid  membrane  backw'ards,  its  lateral  por- 
tions, which  are  fixed  on  each  side  to  the  inner  lip  of  the  upper  border 
of  the  cricoid  cartilage,  become  much  thinner  and  are  found  to  be 
continuous  upwards  with  the  lower  margin  of  the  inferior  or  true  vocal 
cords,  becoming  blended  with  them  firmly  in  front.  These  lateral 
portions  of  the  crico-thyroid  membrane,  described  by  Cruveilhier  as 
\\\e. lateral  crico-thyroid  ligaments,  are  lined  by  the  mucous  membrane 
of  the  larynx,  and  correspond  externally  with  the  lateral  crico-aryte- 
noid  and  adjoining  thyro-arytenoid  muscles. 

On  the  sides,  the  inferior  cornua  of  the  thyroid  cartilage  are  con- 
nected by  two  small  but  distinct  articulations,  having  each  a liga- 
mentous capsule  and  a synovial  membrane,  with  the  sides  of  the  cricoid 
cartilage.  The  prominent  oval  articular  surfaces  of  the  cricoid  car- 
tilage are  directed  upwards  and  outwards,  whilst  those  of  the  thyroid 
cartilage,  which  are  slightly  concave,  look  in  the  opposite  direction. 
The  capsular  fibres  form  a stout  band  behind  this  small  joint,  which 
possesses  but  little  motion. 

The  crico-arytenoid  articulations  are  looser  than  the  crico-thyroid 
just  described.  They  are  surrounded  by  a series  of  thin  capsular 
fibres,  which,  together  with  a loose  synovial  membrane,  serve  to  connect 
the  convex  elliptical  articular  surfaces  on  the  upper  border  of  the  cri- 
coid cartilage  with  the  concave  articular  depressions  seen  on  the  bases 
of  the  arytenoid  cartilages.  There  is,  ntoreover,  a strong  posterior 
crico-arytenoid  ligament  on  each  side,  (fig.  309,  arising  from 

the  cricoid,  and  inserted  into  the  inner  and  back  part  of  the  Base  of 
the  arytenoid  cartilage. 

The  summits  of  the  arytenoid  cartilages  and  the  cornicula  laryngis 
have  usually  a fibrous  and  synovial  capsule  to  connect  them,  but  it  is 
frequently  indistinct. 

Two  yellow  elastic  bands  belonging  to  the  epiglottis,  named  the 
ht/o-epiffloUic  and  thy ro-epi glottic  ligaments,  which  connect  the  epiglot- 
tis in  the  middle  line  with  the  hyoid  bone  and  the  thyroid  cartilage, 
have  already  been  incidentally  noticed.  The  arijteno- epiglottidean 
ligaments  and  the  superior  thyro-arytenoid  ligaments  or  false  vocal 
cords,  both  of  which  are  little  more  than  folds  of  mucous  membrane, 
and  also  the  interior  thyro-arytenoid  ligaments  or  true  vocal  cords, 
will  be  most  conveniently  described  with  the  interior  of  the  larynx. 

Interior  of  the  larynx. — The  superior  aperture  of  the  larynx  (see  fig. 
308),  by  which  it  communicates  with  the  pharynx,  is  a triangular 
opening,  wide  in  front  and  narrow  behind,  the  lateral  margins  of  which 
slope  obliquely  downwards  and  backwards.  It  is  bounded  in  front  by 
the  epiglottis  (e),  behind  by  the  summits  of  the  arytenoid  cartilages  (a) 
and  cornicula  laryngis  with  the  crescentic  border  of  mucous  membrane 
crossing  the  median  space  between  them,  and  on  the  sides  by  two 
folds  of  mucous  membrane,  named  the  aryteno-epiglottidean  folds, 
which,  enclosing  a few  ligamentous  and  muscular  fibres,  pass  forwards 
from  the  tips  of  the  arytenoid  cartilages  and  cornicula  to  the  lateral 
margins  of  the  epiglottis. 


130 


THE  VOCAL  CORDS. 


On  looking  dovv'n  through  the  superior  opening  of  the  larynx,  the 
air-passage  below  this  part  is  seen  to  become  gradually  contracted, 
especially  in  its  transverse  diameter,  so  as  to  assume  the  form  of  a 
long  narrow  fissure  running  from  before  backwards.  This  narrow 
part  of  the  larynx  is  called  the  glottis.  It  is  situated  on  a level  with 
the  lower  part  of  the  arytenoid  cartilages.  Below  it,  at  the  upper 
border  of  the  cricoid  cartilage,  the  interior  of  the  larynx  assumes  an 
elliptical  form,  and  lower  down  still  it  becomes  circular.  The  glottis 
is  bounded  laterally  by  four  strongly  marked  folds  of  the  mucous 
membrane,  stretched  from  before  backwards,  two  on  each  side,  and 
named  the  vocal  cords.  The  superior  vocal  cords  are  much  thinner 
and  weaker  than  the  inferior,  and  are  arched  or  semilunar  in  form  ; 
the  inferior  or  true  vocal  cords  are  thick,  strong,  and  straight.  Be- 
tween the  right  and  left  inferior  vocal  cord  is  the  narrovV  opening  of 
the  glottis,  named  the  rima  glottidis,  and  sometimes  the  glottis  vera,  or 
true  glottis  (fig.  309,^).  Bounded  above  by  the  superior  and  below 
by  the  inferior  vocal  cord  of  each  side,  are  two  deep  oval  depressions, 
seen,  of  course,  one  on  each  side  of  the  glottis,  and  named  the  sinuses, 

or  ventricles  of  the  larynx  (fig. 

' 305,  v)  ; and  lastly,  leading  up- 

wards from  the  anterior  part  of 
these  depressions,  and  on  the 
outer  side  of  the  superior  vocal 
cord,  are  two  small  culs-de-sac, 
named  the  laryngeal  pouches  (s). 
Each  of  these  parts,  which  are 
covered  with  the  mucous  mem- 
brane, requires  a separate  de- 
scription. 

The  superior  vocal  cords,  also 
called  \\\e  false  vocal  cords,  be- 
cause they  are  not  concerned  in 
the  production  of  the  voice,  are 
two  folds  of  mucous  membrane, 
containing  a few  slight  fibrous 
fasciculi,  named  the  superior  thy- 
ro-arytenoid  ligaments.  These  li- 
gaments (above  v,  fig.  305)  are 
fixed  in  front  to  the  depression 
between  the  alas  of  the  thyroid 
cartilage,  somewhat  above  its 
middle  close  to  the  attachment  of 
the  epiglottis;  whilst  behind  they 
are  connected  to  the  tubercles  on 
the  rough  anterior  surface  of 
the  arytenoid  cartilages  (a). 
Above,  they  are  continuous  with 
the  scattered  fibrous  bundles 
contained  in  the  aryteno  epiglot- 
Below,  enclosed  in  the  mucous  membrane,  each  forms 


View  of  the  interior  of  the  left  half  of  the  larynx, 
to  show  the  ventricle  and  laryngeal  pouch.  (After 
Hillon;  Guy’s  Hosp.  Reports,  No.  5.)  a.  Left  ary- 
tenoid cartilage,  c,  c.  Sections  of  the  cricoid  carti- 
lage. (.  Thyroid  cartilage,  e.  Epiglottis,  v.  Left 
ventricle  of  the  larynx,  r.  Left  inferior  or  true  vo- 
cal cord.  s.  Laryngeal  pouch,  b.  Aiyleno-epiglot- 
tidean  muscle,  or  compressor  sacculi  laryngis.  /. 
inside  of  trachea,  which  has  been  added  to  this 
figure. 

tidean  folds. 


LIGAMENTS  OF  THE  LARYNX. 


131 


a free  crescentic  margin,  which  hounds  the  corresponding  veniricle  of 
the  larynx,  the  aperture  of  which  is  seen  on  looking  down  into  the 
laryngeal  cavity,  because  the  superior  vocal  cords  are  separated  farther 
from  each  other  than  the  inferior  cords. 

The  inferior  or  true  vocal  cords  (fig.  305,  r ; 309,  ^ ®),  for  it  is  by 
their  vibration  that  the  voice  is  produced,  are  two  bands  of  elastic 
tissue,  named  the  inferior  thyro- arytenoid  ligaments,  which  are  at- 
tached in  front  to  about  the  middle  of  the  depression  between  the 
alas  of  the  thyroid  cartilage  below  the  superior  cords,  and  are  inserted 
behind  to  the  elongated  anterior  processes  of  the  base  of  the  arytenoid 
cartilages.  These  bands  consist  of  closely  arranged  parallel  fibres. 
They  are  continuous  below  with  the  thin  lateral  portions  of  the  crico- 
thyroid membrane;  on  their  outer  side  they  are  in  contact  with  and 
connected  to  the  fibres  of  the  thyro-arytenoid  muscles ; in  other  direc- 
tions they  are  free,  and  arc  covered  by  the  mucous  membrane,  which 
is  here  so  thin  and  closely  adherent  as  to  show  the  white  colour  of 
these  ligaments  through  it.  Their  upper  and  free  edges,  which  are 
sharp  and  straight,  form  the  lower  boundaries  of  the  ventricles,  and 
are  the  parts  thrown  into  vibration  during  the  production  of  the  voice. 
The'ir  inner  surfaces  are  flattened,  and  look  towards  each  other. 

[Several  years  since  I published  a description*  of  the  arrangement  of  the 
ligamentous  structure  of  the  larynx,  in  which  the  existence  of  the  vocal  cords  is 
denied,  to  which  opinion  I still  adhere. 

“ If  the  muscular  layer,’’  which  is  placed  beneath  the  alee  of  the  thyroid  carti- 
lage, “be  raised  up,  the  crico-thyroid  membrane  (fig.  306,)  will  be  exposed. 


Fig.  306. 


Represents  the  right  ala  of  the  thyroid  cartilage  thrown  forward,  the  muscles  removed,  and 
the  membrana  vocalis  exposed. 

This  will  be  found  to  have  its  origin  from  the  inner  circumference  of  the  superior 
edge  of  the  cricoid  cartilage  anterior  to  the  arytenoid  cartilages,  and  from  the 
anterior  part  of  the  bases  of  the  latter,  and  to  have  its  insertion  into  the  interior 
half  of  the  entering  angle  of  the  thyroid  cartilage.  Its  internal  face  is  in  contact 
with  the  lining  or  mucous  membrane  of  the  larynx,  and  a good  view  of  it  may 
be  obtained  by  removmg  the  latter.  Its  anterior  inferior  part  is  thickened  and 

» Am.  Journ.  of  Med.  Sci.,  vol,  xii.  No.  23,  N.  S.  p.  141.  Philada.  1846. 


132 


VENTRrCLES  OF  THE  LARYNX. 


pierced  by  several  foramina  for  the  transmission  of  blood-vessels ; its  superior 
edge  is  also  a little  thickened,  and  is  on  a line  with  the  inferior  edge  of  the  opening 
of  the  ventricle  of  the  larynx,  constituting  what  is  generally  described  as  a 
distinct  structure,  under  the  name  of  the  inferior  thyro-arytenoid  ligaments  or 
vocal  cords,  but  which,  as  such,  really  do  not  exist.  More  properly  this  membrane 
cannot  be  considered  to  stop  here,  as  it  may  be  traced,  though  in  a very  thinned 
condition,  over  the  whole  periphery  of  the  ventricle  of  the  larynx,  even  so  far  as 
the  epiglottis.’’ 

A little  thickening  in  this  membrane  at  the  line  corresponding  to  the  superior 
edge  of  the  orifice  of  the  ventricle  of  the  larynx  produces  the  so-called  superior 
thyro-arytenoid  ligaments. 

This  membrane,  which  may  be  called  the  vocal  membrane  (membrana  vocalis), 
throughout  its  whole  extent  is  composed  of  the  yellow  elastic  tissue,  but  above 
the  inferior  edge  of  the  ventricle  of  the  larynx  is  intermingled  with  a good  pro- 
portion of  areolar  tissue. — J.  L.] 

The  rima  glottidis  (fig.  309,*),  an  elongated  fissure  formed  between 
the  inferior  or  true  vocal  cords,  and,  posteriorly,  between  the  bases  of 
the  arytenoid  cartilages,  is,  when  slightly  open,  of  a lancet-shape,  the 
pointed  extremity  being  turned  forwards ; when  further  opened  it  is 
triangular,  becoming  widened  behind;  and  in  its  fully  dilated  condition 
it  has  the  figure  of  an  elongated  lozenge,  with  its  posterior  angle  trun- 
cated. This  aperture  is  the  narrowest  part  of  the  interior  of  the 
larynx;  in  the  adult  male  it  is  about  eleven  lines,  or  nearly  an  inch  in 
its  antero-posterior  measurement,  and  about  four  lines  across  at  its 
widest  part,  which  may  be  dilated  to  nearly  half  an  inch.  In  the 
female  its  dimensions  are  less,  its  antero-posterior  diameter  being  about 
eight  lines,  and  its  transverse  diameter  about  two.  The  vocal  liga- 
ments, which  are  shorter  than  the  glottis,  measure  about  seven  lines 
in  the  male  and  five  in  the  female. 

The  ventricles,  or  sinuses  of  the  larynx  (fig.  305,  rj),  [ventriculi 
Galeni  s.  Morgagni,]  formed  between  the  superior  and  inferior  vocal 
cords  on  each  side,  are  two  oblong  cavities,  narrower  at  their  orifice 
than  in  their  interior.  The  upper  margin  of  each  is  crescentic,  and 
the  lower  straight ; the  outer  surface  is  covered  by  the  upper  fibres  of 
the  corresponding  thyro-arytenoid  muscle. 

The  small  culs-de-sac,  named  the  laryngeal  pouches  (s),  lead  from 
the  anterior  part  of  the  ventricle  upwards,  for  the  space  of  half  an 
inch,  between  the  superior  vocal  cords  on  the  inner  side,  and  the  thy- 
roid cartilage  on  the  outer  side,  reaching  as  high  as  to  the  upper 
border  of  that  cartilage  at  the  sides  of  the  epiglottis.  Each  of  these 
supplementary  cavities  is  conical  in  shape,  and  curved  slightly  back- 
wards, so  as  to  have  been  compared  in  form  to  a Phrygian  cap.  Its 
opening  into  the  corresponding  ventricle  is  narrow,  and  is  generally 
limited  by  two  folds  of  the  lining  mucous  membrane.  Numerous 
small  glands,  sixty  or  seventy  in  number,  open  into  its  interior,  and  it 
is  surrounded  by  a quantity  of  fat.  Externally  to  the  fat,  this  little 
pouch  receives  a fibrous  investment,  which  is  continuous  below  with 
the  superior  vocal  cord.  Over  its  laryngeal  side  and  upper  end,  is  a 
thin  layer  of  muscular  fibres  (compressor  sacculi  laryngis,  arytasno- 
epiglottideus  inferior;  Hilton)  connected  above  with  those  found  in 
the  aryteno-epiglottidean  folds  (6).  The  upper  fibres  of  the  thyro- 
arytenoid muscles  pass  over  the  outer  side  of  the  pouch,  some  few 


MUSCLES  OF  THE  LARYNX. 


133 


being  attached  to  its  lower  part  Lastly,  the  laryngeal  pouch  is  sup- 
plied abundantly  with  nerves,  derived  from  the  superior  laryngeal. 


Besides  certain  extrinsic  muscles  already  described,  viz. : the  sterno- 
hyoid, omo-hyoid,  sterno-thyroid,  and  thyro-hyoid  muscles,  together 
with  the  muscles  of  the  supra-hyoid  region,  and  the  middle  and  inferior 
constrictors  of  the  pharynx,  all  of  which  act  more  or  less  upon  the 
entire  larynx,  there  are  certain  intrinsic  muscles  which  move  the 
different  cartilages  upon  one  another.  These  intrinsic  muscles  are  the 
crico-thyroid,  the  'posterior  crico- arytenoid,  the  lateral  crico-arytenoid, 
the  thyro-arytenoid,  and  the  arytenoid,  together  with  certain  slender 
muscular  fasciculi  connected  with  the  epiglottis.  All  these  muscles, 
except  the  arytenoid,  which  crosses  the  middle  line,  exist  in  pairs. 

The  crico-thyroid  muscle  (crico-thyroideus,  fig.  307,  k),  is  a short 
thick  triangular  muscle,  seen  on  the  front  of  the  larynx,  situated  on 


Side  view  of  the  thyroid  (e,  g)  and  cricoid  (a,  b)  cartilages,  with  part  of  the  trachea,  m,  n, 
crico-thyroid  membrane  or  ligament,  k,  crico-thyroid  muscle. — C.] 

the  fore  part  and  side  of  the  cricoid  cartilage.  It  arises  by  a broad 
origin  from  the  cricoid  cartilage,  reaching  from  the  median  line  back- 
wards upon  the  lateral  surface,  and  its  fibres,  passing  obliquely 
upwards  and  outwards  and  diverging  slightly,  are  inserted  into  the 
lower  border  of  the  thyroid  cartilage,  from  the  tubercle  on  each  side 
of  the  median  notch  to  the  lesser  cornu,  and  also  into  the  anterior 
border  of  the  latter  process.  The  fibres  of  insertion  reach  from  half 
VOL.  II.  12 


Muscles  of  the  Larynx. 


[Fig.  .S07 


134 


LATERAL  CRICO-ARYTENOID. 


Fiff.  308. 


a line  to  a line  upon  the  inner  surface  of  the  thyroid  cartilage.  The 
lower  portion  of  the  muscle,  which  is  nearly  horizontal  in  direction, 
and  is  inserted  into  the  lesser  cornu,  is  usually  distinct  from  the  rest. 
Some  of  the  superficial  fibres  are  almost  always  continuous  with  the 
inferior  constrictor  of  the  pharynx. 

The  inner  borders  of  the  muscles  of 
the  two  sides  are  separated  from  each 
other  in  the  middle  line  by  a triangular 
interval,  broader  above  than  below,  and 
occupied  by  the  crico-thyroid  mem- 
brane. The  crico-thyroid  muscle  is 
covered  by  the  sterno-thyroid,  and  it 
covers  the  fore  part  of  the  lateral 
crico-arytenoid  and  thyro-arytenoid 
muscles:  its  lower  border  is  in  contact 
with  or  covered  by  the  thyroid  body, 
and  its  upper  border  adjoins  the  inferior 
constrictor  of  the  pharynx. 

The  posterior  crico-arytenoid  muscle 
(crico-arytsenoideus  posticus,  fig.  308, 
h),  is  found  at  the  back  of  the  larynx 
beneath  the  mucous  membrane  in  that 
situation.  It  arises  from  the  broad  de- 
pression seen  on  the  corresponding  half 
of  the  posterior  surface  of  the  cricoid 
cartilage.  From  this  broad  origin  its 
fibres  converge  upwards  and  outwards 
towards  the  base  of  the  arytenoid  car- 

Posterior  view  of  larynx,  and  part  of  tilage.  The  Upper  fibres  are  short 

trachea,  dissected  to  show  the  muscles.  j i i.  i • * i 

a.  Right  arytenoid  cartilage,  t,  t.  Poste-  RRO.  RllTlOSt  horizontal  ^ tho  micldlo  RTG 
rior  margins  of  thyroid  cartilage,  c.  Back  the  longest  and  run  obliquely;  whilst 

Epigionif  1!  Ldf%ostr°o\^^r'ico!arytei  the  lower  or  anterior  fibres  are  nearly 
noid  muscle,  s.  Arytenoid  muscle.  1.  vertical.  The  muscle  is  inserted  (fig. 
Fibrous  membrane  at  back  of  trachea,  4\  u 

■with  the  glands  lying  in  it.  n.  Muscular  ^09,  ) by  3-  narrow  slip,  pai  tly  flosh^  and 
fibres  of  the  trachea,  r.  Cartilaginous  partly  tendinous,  into  the  external  pro- 
rings  of  trachea.  cess,  or  posterior  and  outer  surface  of 

the  base  of  the  arytenoid  cartilage,  behind  the  attachment  of  the  lateral 
crico-arytenoid  muscle.  This  muscle  is  situated  between  the  pharyn- 
geal mucous  membrane  and  the  cricoid  cartilage. 

The  lateral  crico-arytenoid  muscle  (crico-arytsenoideus  lateralis,  figs. 
309;®  310,®). — To  obtain  a proper  view  of  this  muscle  and  the  thyro- 
arytenoid, which  will  be  next  described,  it  is  necessary  to  remove  the 
corresponding"  ala  of  the  thyroid  cartilage,  by  which  they  are  in  a 
great  measure  hidden.  The  lateral  crico-arytenoid  is  smaller  than 
the  posterior,  and  is  of  an  oblong  form.  It  arises  from  the  upper 
border  of  the  side  of  the  cricoid  cartilage,  its  origin  extending  as  far 
back  as  the  articular  surface  for  the  arytenoid  cartilage.  Its  fibres 
passing  obliquely  backwards  and  upwards,  the  anterior  or  upper  ones 
being  the  longest,  are  attached  to  the  external  process  or  outer  side  of 
the  base  of  the  arytenoid  cartilage  and  to  the  adjacent  part  of  its  an- 


THYRO-ARYTENOID. 


135 


terior  surface,  in  front  of  the  insertion  of  the  posterior  crico-arytenoid 
muscle. 

This  muscle  lies  in  the  interval  between  Fig.  309. 

the  ala  of  the  thyroid  cartilage  and  the 
interior  of  the  larynx,  being  lined  w'ithin 
by  the  mucous  membrane  of  the  larynx. 

Its  anterior  part  is  covered  by  the  upper 
part  of  the  crico-thyroid  muscle.  The 
upper  border  is  in  close  contact,  and  in- 
deed, is  sometimes  blended  with  the  thyro- 
arytenoid muscle. 

The  thyro-arytenoid  (thyro-arytsenoi- 
deus,  figs.  309  310,’')  is  a broad  flat  mus- 

cle situated  above  the  lateral  crico-aryte- 
noid. It  is  thick  below  and  in  front,  and 
becomes  thinner  upwards  and  behind.  It  ^ 
consists  of  several  muscular  fasciculi,  Willis,  showing  a bird’s-eye  view  of 

which  arise  in  front  from  the  internal  [he  interior  oi  larynx,  i.  opening  of 
- r } I -1  -1  r I ine  glottis.  2,  2.  Arytenoid  cartilages, 

surlace  ot  the  thyroid  cartilage,  from  the  3.  3.  Vocal  cords.  4,  4.  Posterior 

lower  two-thirds  of  the  retreating  angle  "'co-aryienoid  muscles.  5 Right 
- 1 1 I - - c I ° 1 lateral  crico-arylenoid  muscle;  that 

formed  by  the  junction  of  the  two  alas,  of  the  left  side  is  removed.  6.  Ary- 
They  extend  almost  horizontally  back-  'enoid  muscle.  7.  Thyro-arylenoid 
, , I ’i  1 muscle  of  the  left  side  ; that  of  the 

wards  and  outwards  to  reach  the  base  right  side  is  removed.  8.  Upper 

of  the  arytenoid  cartilage.  The  /outer  parhhige.  9, 9. 

r I 1 ^ I • I r Upper  border  and  back  of  the  cncoid 

portion  of  the  muscle,  which  forms  a cartilage.  13.  Posterior  crico-aryte- 
thick  fasciculus,  receives  a few  addi-  ligament. 


tional  fibres  from  the  posterior  surface 

of  the  crico-thyroid  membrane,  and  is  inserted  into  the  anterior  pro- 
jection on  the  base  of  the  arytenoid  cartilage  and  to  the  adjacent  part 
of  the  surface  close  to  the  insertion  of  the  lateral  crico-arytenoid  mus- 
cle. The  thinner  portion  of  the  thyro-arylenoid  muscle  is  inserted 
higher  up  on  the  anterior  surface  and  outer  border  of  that  cariilage. 
The  lower  portion  of  the  muscle  lies  parallel  with  the  rima  glotlidis, 
immediately  on  the  outer  side  of  the  corresponding  true  chorda  vocalis 
with  which  it  is  intimately  connected,  and  into  the  outer  surface 
of  which  some  of  its  fibres  are  inserted.  According  to  some  authori- 
ties, however,  the  cord  and  muscle  can  be  completely  separated.  The 
upper  thin  portion  lies  upon  the  outer  side  of  the  corresponding  laryn- 
geal pouch  and  ventricle  close  beneath  the  mucous  membrane.  The 
entire  muscle  may  be  dissected  indeed  from  the  interior  of  the  larynx 
by  raising  the  mucous  membrane  and  vocal  cord.  Its  outer  surface 
is  covered  by  a loose  cellular  tissue,  w'hich  separates  it  from  the  in- 
ternal surface  of  the  ala  of  the  thyroid  cariilage.  Some  of  the  fibres 
of  this  muscle  pass  round  the  border  of  the  arytenoid  cartilage,  and 
become  continuous  with  some  of  the  oblique  fibres  of  the  arytenoid 
muscle,  to  be  presently  described. 


Santorini  described  three  thyro-arytenoid  muscles,  an  inferior  and  middle,  which 
are  constant,  and  a superior,  as  sometimes  present.  The  fibres  of  the  superior 
fasciculus,  when  present,  arise  nearer  to  the  notch  of  the  thyroid  cartilage,  and 
are  attached  to  the  upper  part  of  the  arytenoid  cartilage.  This  is  named  by 


136 


MUSCULAR  FIBRES  CONNECTED  WITH  THE  EPIGLOTTIS. 


ScDinmerring  the  small  thyro-arytenoid,  whilst  the  two  other  portions  of  the  muscle 
constitute  the  gi'cat  thyro-arytenoid  of  that  author. 

Muscular  fibres  connected  with  the  'epiglottis. — Under  the  name  of 
thyro-epiglottideus  and  arytceno-epighttideus  muscle,  some  thin  scat- 
tered fasciculi  have  been  noticed  and  described  by  anatomists,  as  ex- 
tending on  each  side  from  the  thyroid  and  arytenoid  cartilages  to  the 
corresponding  margin  of  the  epiglottis.  The  thyro-epiglottidean  fibres 
arise  from  the  inner  surface  of  the  thyroid  cartilage  close  upon  the  outer 
side  of  the  origin  of  the  thyro-arytenoid  muscle,  and  ascend  to  reach 
the  margin  of  the  epiglottis.  They  constitute  the  depressor  epiglottidis. 
The  arytceno-epiglottidean  fibres  (fig.  305,  b)  arise  from  the  corre- 
sponding arytenoid  cartilage  just  above  the  point  of  attachment  of  the 
superior  vocal  cord,  and  passing  forwards  spread  out  so  as  to  cover 
the  upper  end  and  part  of  the  side  of  the  laryngeal  pouch  on  its  laryn- 
geal aspect,  and  are  finally  inserted  by  a broad  expanse  into  the  mar- 
gin of  the  epiglottis.  That  part  of  the  muscle  which  covers  the  pouch 
was  described  by  Mr.  Hilton  as  the  arytoeno-epiglotUdeus  inferior  or 
compressor  sacculi  laryngis,  and  is  stated  by  him  to  be  distinguished 
by  a cellular  interval  from  another  fasciculus  of  fibres  situated  higher 
up  in  the  aryteno-epiglottidean  folds,  which  might  be  named  the  ary- 
tceno-epiglottideus  superior.  Sometimes  a few  of  the  fibres  of  the  ary- 
teno-epiglottidean muscle  appear  to  be  continuous  round  the  outer 
border  of  the  arytenoid  cartilage  with  some  of  the  oblique  fasciculi  of 
the  arytenoid  muscle. 


[Fig.  310. 


Represents  the  larynx  with  the  right  ala  (1)  detached  from  its  connexions  and  thrown  for- 
wards, exhibiting  the  muscular  layer  beneath.  2.  The  ericoid  cartilage.  3.  The  right  arytenoid 
cartilage.  4 Epiglottis.  f>.  Cririo-thyroideus  muscle.  6.  Crico  arytsenoideus  lateralis.  7.  Thyro- 
aryltenoideus,  with  the  thyro-epiglottidean  layer  of  muscular  fibres  passing  from  its  upper  part. 
8 Aryteno-epiglottidean  layer  of  muscular  fibres.  9 Inferior  anterior  part  of  the  crico  thyroid 
or  vocal  membrane.  10.  Acetabulum  for  the  articulation  of  the  inferior  cornu  of  the  thyroid 
with  the  cricoid  cartilage. — J.  L.J 


ARYTENOID  MUSCLE. 


137 


[The  muscular  fibres  connected  with  the  epiglottis  are  presented  in  various 
conditions  of  development  in  different  larynges.  The  thyro-epiglottidean  layer 
of  fibres,  (fig.  310,)  appears  to  be  constituted  by  the  divergence  of  the  fibres  of 
the  upper  edge  of  the  thyro-arytenoid  muscle  (')  having  the  origin  at  the  entering 
angle  of  the  thyroid  cartilage,  and  the  expanded  edge  terminating  in  the  areolar 
tissue,  between  the  fold  of  mucous  membrane  extending  from  the  tip  of  the  ary- 
tenoid to  the  epiglottis  cartilage  and  in  the  margin  of  the  latter.  Frequently  these 
fibres  are  indistinct  and  occasionally  do  not  exist  at  all.  The  aryteno-epiglotti- 
dean  fibres  (®)  usually  form  a thin  layer,  lying  e.xternal  to  the  e.xpanded  portion 
of  the  thyro-epiglottidean  layer,  and  attached  to  the  outer  side  of  the  arytenoid 
cartilcige  at  one  extremity,  and  to  the  margin  of  the  epiglottis  at  the  other.  Fre- 
quently this  layer  is  separated  into  two  bands  by  an  interspace  of  areolar  tissue. 
The  upper  band  (arytseno-epiglottideus  superior)  is  usually  the  smaller;  the  lower 
(arytasno-epiglottideus  inferior  s.  compressor  sacculi  laryngis)  is  sometimes  rein- 
forced by  accessory  fibres  from  the  fhyro-arytaenoideus,  or  by  a distinct  band 
carving  backwards  from  the  entering  angle  of  the  thyroid  cartilage.  Occasionally 
the  aryteno-epiglottidean  layer  is  indistinct,  or,  consists  only  of  a few  scattered 
fibres. — J.  L.] 

The  arytenoid  musde  (aryttenoideus,  fig.  308,  s),  the  only  single 
muscle  belonging  to  the  larynx,  is  situated  beneath  the  mucous  mem- 
brane on  the  back  of  this  organ,  lying  upon  the  posterior  concave  sur- 
faces of  the  arytenoid  cartilages,  and  stretching  across  the  interval 
betvt'cen  them.  This  muscle,  which  is  short  and  thick,  arises  from  the 
whole  length  of  the  outer  border  and  posterior  surface  of  one  aryte- 
noid cartilage,  and  is  inserted  in  the  corresponding  parts  of  the  other 
cartilage.  It  consists  of  three  sets  of  fibres:  one  transverse,  and  two 
oblique.  The  transverse  fibres  (arytrenoideus  transversus),  the  deepest 
and  most  numerous,  pass  straiglit  across,  whilst  the  two  sets  of  oblique 
fibres  (arytsenoideus  obliquus)  pass  from  the  base  of  one  cartilage  to 
the  apex  of  the  opposite  one,  crossing  each  other  in  the  middle  line 
superficially  to  the  transverse  set.  Some  of  these  oblique  fibres  be- 
come continuous  round  the  side  of  the  arytenoid  cartilage  with  fibres 
of  the  thyro-arytenoid  and  aryteno-epiglottic  muscles,  as  already  men- 
tioned. 

The  lower  border  of  the  arytenoid  muscle  touches  the  cricoid  carti- 
lage, from  which  a few  muscular  fibres  generally  arise;  its  posterior 
surface  is  covered  by  the  pharyngeal  mucous  membrane,  which  is 
prolonged  over  its  upper  border  and  a small  part  of  its  anterior  sur- 
face between  the  arytenoid  cartilages,  to  be  continued  into  the  interior 
of  the  larynx. 

ACTION  or  THE  INTRINSIC  MUSCLES  OF  THE  LARYNX. 

The  two  crico-thyroid  muscles  (fig.  307,i")  must  cause  the  thyroid  and  cricoid 
cartilages  to  turn  on  each  other  at  their  posterior  articulation,  whereby  they  are 
made  to  approach  in  front,  whilst  the  summit  of  the  cricoid  behind  is  carried  for- 
wards upon  the  cricoid,  or,  vice  versa,  the  cricoid  backwards  from  the  thyroid ; 
and  since  the  arytenoid  cartilages  are  moved  backwards  together  with  the  cri- 
coid, in  consequence  of  their  connexion  to  it  by  the  strong  posterior  crico-aryte- 
noid  ligaments,  the  action  of  the  crico-thyroid  muscles  will  be  to  elongate  and 
tighten  the  vocal  cords.  Tire  posterior  crico- arytenoid  muscles  (fig.  309, cause 
the  arytenoid  cartilages  to  swing  upon  their  base  with  a rotatory  movement  out- 
wards and  backwards,  which  is  not  hindered  by  the  aforesaid  ligament,  so  that 
tbeir  anterior  processes,  together  with  the  attached  vocal  cords,  part  from  each 
other,  and  the  opening  of  the  glottis  is  thus  dilated.  The  lateral  crico-arytenoid 
muscles  (^^)  swmg  the  arytenoid  cartilages  back  again  in  the  opposite  direction  to 


138 


tMUCOUS  MEMBRANE  OF  LARYNX. 


the  last-named  muscles,  so  as  to  approximate  their  anterior  extremities,  and  thus 
contract  the  opening  of  the  glottis. 

The  thjro-anjtcnoid  muscles  (’)  also  bring  the  anterior  processes  of  the  aryte- 
noid cartilages  together,  and  thus  constrict  the  glottis.  According  to  Mr.  Willis, 
their  further  and  chief  action,  is  to  draw  forwards  the  arytenoid  cartilages,  with 
the  back  part  of  the  cricoid  cartilage,  to  which  these  are  affixed,  and  thus  to 
cause  the  cricoid  cartilage  to  turn  on  the  inferior  cornua  of  the  thyroid,  by  which 
means  the  crico-thyroid  interval  in  front  is  increased,  and  the  vocal  cords  are 
shortened  and  relaxed ; but,  according  to  another  opinion,  it  has  been  conceived 
that  these  muscles  tighten  the  cords  by  the  rotation  inwards  of  the  arytenoid 
cartilages,  or  by  the  action  of  some  fibres  supposed  to  be  attached  to  the  outer 
surface  of  the  cords. 

The  single  arytenoid  muscle  (“)  approximates  the  arytenoid  cartilages,  and  thus 
constricts  the  posterior  part  of  the  rima  glottidis.  The  tendency  of  some  of  its 
fibres,  but  especially  the  superficial  and  oblique  ones,  to  rotate  the  arytenoid 
cartilages  outwards,  and  thus,  by  drawing  more  apart  their  anterior  processes,  to 
widen  the  opening  of  the  glottis,  is  counteracted  by  the  lateral  crico-arytenoid 
muscles.  The  few  scattered  fibres  of  the  arytenoid  muscle,  which,  together  with 
those  of  the  thyro-arytenoid  and  aryteno-epiglotlidean  muscles,  encircle  as  it  were 
the  upper  part  of  the  larynx,  must  tend  to  contract  its  superior  aperture.  The 
fasciculi  of  the  thyro-arytaenoidei  on  the  outer  side,  and  those  of  the  arytaeno-epi- 
glottidei  (fig.  305,  b)  upon  the  summit  and  inner  sides,  of  the  laryngeal  pouches, 
will  serve  to  compress  these  sacs. 

Lastly,  the  thyro-epiglottideij  so  far  as  they  operate,  are  depressors  of  the  epi- 
glottis. 

The  mucous  membrane  and  glands  of  the  larynx. — The  mucous 
membrane  of  the  larynx  is  continuous  above  with  that  of  the  mouth 
and  pharynx,  and  below  with  that  of  the  trachea.  Reaching  the 
anterior  surface  and  sides  of  the  epiglottis,  from  the  root  of  the 
tongue,  it  forms  the  three  glosso-epiglottidean  folds,  and  is  then  re- 
flected over  the  posterior  or  laryngeal  surface  of  the  epiglottis.  From 
the  margins  of  the  epiglottis  to  the  summits  of  the  arytenoid  carti- 
lages, it  forms  the  aryteno-epiglottidean  folds,  or  lateral  boundaries  of 
the  superior  aperture  of  the  larynx.  Lastly,  in  the  notch  between  the 
summits  of  the  arytenoid  cartilages,  it  turns  over  the  upper  border  of 
the  arytenoid  muscle.  Sinking  thus  into  the  larynx  (see  fig.  305),  it 
turns  over  the  superior  vocal  cords,  lines  the  ventricles  and  sacculi 
laryngis,  and  is  then  reflected  over  the  inferior  vocal  cords  (?•),  below 
which  it  descends  {d)  upon  the  lateral  and  middle  portions  of  the 
crico-thyroid  membrane,  and  finally  lines  the  entire  inner  surface  of 
the  cricoid  cartilage  (c  c). 

The  laryngeal  mucous  membrane  is  thin  and  of  a pale  pink 
colour.  In  some  situations  it  adheres  intimately  to  the  subjacent 
parts,  especially  on  the  epiglottis,  and  still  more  in  passing  over  the 
true  vocal  cords,  on  which  it  is  extremely  thin  and  most  closely 
adherent.  About  the  upper  part  of  the  larynx,  above  the  glottis,  it  is 
extremely  sensitive.  In  or  near  the  aryteno-epiglottidean  folds  it 
covers  a quantity  of  loose  cellular  tissue,  which  is  liable  in  disease  to 
infiltration,  constituting  oedema  of  the  glottis.  Like  the  mucous  mem- 
brane in  the  rest  of  the  air  passages,  that  of  the  larynx  is  covered  in 
the  greater  part  of  its  extent  with  a columnar  ciliated  epithelium,  by 
the  vibratory  action  of  which  the  mucus  is  urged  upwards.  The 
cilia  are  found  higher  up  in  front  than  on  each  side  and  behind,  reach- 
ing in  the  former  direction  as  high  as  the  widest  portion  of  the  epi- 


DEVELOPMENT  OF  LARYNX. 


]39 


glottis,  and  in  other  directions,  to  a line  or  two  above  the  border  of  the 
superior  vocal  cords:  higher  tlian  these  points  the  epithelium  loses  its 
cilia,  and  gradually  assumes  a squamous  form,  like  that  of  the  pharynx 
and  m.outh. 

Glands. — The  lining  membrane  of  the  larynx  is  provided  with 
numerous  glands,  which  secrete  an  abundant  mucus;  and  the  orifices 
of  which  may  be  seen  almost  everywhere,  excepting  upon  and  near 
the  true  vocal  cords.  They  abound  particularly  upon  the  epiglottis 
(fig.  308,  e)  in  the  substance  of  which  are  found  upwards  of  fifty  little 
compound  glands.  Between  the  anterior  surface  of  the  epiglottis,  ihe 
os  hyoides,  and  the  root  of  the  tongue,  is  a mass  of  yellowish  fat,  erro- 
neously named  the  epiglottidean  gland,  in  or  upon  which  some  real 
glands  may  exist.  Another  collection  of  glands,  named  arytenoid,  is 
placed  within  the  fold  of  mucous  membrane  in  front  of  each  arytenoid 
cartilage,  from  which  a series  may  be  traced  forwards,  along  the  cor- 
responding superior  vocal  cord.  The  glands  of  the  laryngeal  pouches 
have  already  been  described. 

Vessels  and  JVerves  of  the  Larynx. 

The  arteries  of  the  larynx  are  derived  from  the  superior  thyroid, 
a branch  of  the  external  carotid,  and  from  the  inferior  thyroid,  a 
branch  of  the  subclavian.  The  veins  join  the  superior,  middle,  and  in- 
terior thyroid  veins.  The  lymphatics  are  numerous  and  pass  through 
the  cervical  glands.  The  rierves  are  supplied  from  the  superior  laryn- 
geal and  inferior  or  recurrent  laryngeal  branches  of  the  pneumogastric 
nerve,  joined  by  branches  of  the  sympathetic.  The  superior  laryngeal 
nerves  supply  the  mucous  membrane,  and  also  the  crico-thyroid  mus- 
cles, and  in  part  the  arytenoid  muscle.  The  inferior  laryngeal  nerves 
supply,  in  part,  the  arytenoid  muscle,  and  all  the  other  muscles,  ex- 
cepting the  crico-thyroid. 

The  superior  and  inferior  laryngeal  nerves  of  each  side  communi- 
cate with  each  other  in  two  places,  viz.,  at  the  back  of  the  larynx,  be- 
neath the  pharyngeal  mucous  membrane,  and  on  the  side  of  the 
larynx,  under  the  ala  of  the  thyroid  cartilage. 

DEVELOPMENT  AND  GROWTH  OF  THE  LARYNX. 

Development. — ^The  rudimentary  larynx  consists,  according  to  Valentin,  of  two 
slight  enlargementshaving  a fissure  between  them,  and  embracing  the  entrance 
from  the  (Esophagus  into  the  trachea.  According  to  Reichert,  the  rudiments  of 
the  arytenoid  cartilages  are  the  first  to  appear.  Rathke,  however,  states  that  aU 
the  cartilages  form  at  the  same  time,  and  are  recognisable  together  as  the  larynx 
enlarges,  the  epiglottis  appearing  last.  In  the  human  embryo,  Fleischmann  could 
not  detect  the  cartilages  at  the  seventh  week,  though  the  larynx  was  half  a line 
in  length,  but  at  the  eighth  week  there  were  visible  the  thyroid  and  cricoid  car- 
tilages, consisting  then  and  afterwards  of  two  lateral  halves,  which  are  united 
together  by  the  sixth  month. 

Growth. — During  childhood  the  growth  of  the  larynx  is  very  slow.  Richerand 
found  that  there  was  scarcely  any  difference  between  the  dimensions  of  this 
organ  in  a child  of  three  and  in  one  of  twelve  years  of  age.  Up  to  the  age  of 
puberty  the  larynx  is  similar  in  the  male  and  female,  the  chief  characteristics  at 
that  period  being  the  small  size  and  comparative  slightness  of  the  organ,  and  the 
smooth  rounded  form  of  the  thyroid  cartilage  in  front.  In  the  female  these  con- 
ditions are  permanent,  expecting  that  a slight  increase  in  size  takes  place.  In  the 


140 


THE  THYROID  BODY. 


male,  on  the  contrary,  remarkable  changes  rapidly  occur,  and  the  larynx  speedily 
becomes  more  prominent  and  more  perceptible  at  the  upper  part  of  the  neck. 
Its  cartilages  become  larger,  thicker,  and  stronger,  and  the  alee  ol  the  thyroid 
cartilage  project  forward  in  front  so  as  to  form  at  their  union  with  one  another,  at 
an  acme  angle,  the  prominent  ridge  named  pomitm  Adami.  At  the  same  time  the 
median  notch  on  its  upper  border  is  considerably  deepened.  In  consequence  of 
these  changes  in  the  thyroid  cartilage,  the  distance  between  its  angle  in  front  and 
the  arytenoid  cartilages  behind  becomes  greater,  and  the  chordee  vocales  are 
necessarily  lengthened.  Hence  the  dimensions  of  the  glottis,  which,  at  the  time 
of  puberty,  are  increased  by  about  one-third  only  in  the  female,  are  nearly 
doubled  in  the  male,  and  the  adult  male  larynx  becomes  altogether  one-third 
larger  than  that  of  the  female. 

Towards  the  middle  of  life,  the  cartilages  of  the  larynx  first  show  a tendency 
to  ossification ; this  commences  first  in  the  thyroid  cartilage,  then  appears  in  the 
cricoid,  and  lastly  in  the  arytenoid  cartilages.  In  the  thyroid  cartilage  the  ossifi- 
cation usually  begins  at  the  cornua  and  posterior  borders:  it  then  gradually  e.x- 
tends  along  the  whole  inferior  border,  and  subsequently  spreads  upwards  through 
the  cartilage.  The  cricoid  cartilage  first  becomes  ossified  at  its  upper  border 
upon  each  side,  near  the  two  posterior  auricular  eminences,  and  the  ossification 
invades  the  lateral  parts  of  the  cartilage  before  encroaching  on  it  either  in  front 
or  behind.  The  arytenoid  cartilages  become  ossified  from  below  upwards. 

TIIK  THYROID  BODY. 

The  thyroid  body  is  a soft,  reddish,  and  highly  vascular  organ, 
situated  in  the  lower  part  of  the  neck,  embracing  the  front  and  sides 
of  the  upper  part  of  the  trachea,  and  reaching  up  to  the  sides  of  the 
larynx.  Prom  ils  general  resemblance  to  the  glandular  organs,  it  has 
been  called  ihe  thyroid  gland,  but  it  possesses  no  syslem  of  excretory 
ducts.  Its  function  is  unknown,  but,  owing  to  its  local  connexion 
with  the  principal  cartilage  of  the  larynx,  is  usually  described  with 
that  organ,  and  has  received  the  name  thyroid.  It  is  of  an  irregular, 
semilunar  form,  consisting  of  two  lateral  lobes,  united  together  towards 
their  lower  ends  by  a transverse  portion  named  the  isthmus.  Viewed 
as  a whole,  the  thyroid  body  is  convex  on  the  sides  and  in  front, 
forming  a rounded  projection  upon  the  trachea  and  larynx.  It  is 
covered  hy  the  sterno-hyoid,  sterno-thyroid,  and  omo-hyoid  muscles, 
and  behind  them  it  comes  into  contact  with  the  sheath  of  the  great 
vessels  of  the  neck.  Its  deep  surface  is  concave  where  it  rests  against 
the  trachea  and  larynx.  It  usually  extends  so  far  back  as  to  touch 
the  lower  portion  of  the  pharynx,  and  on  the  left  side  the  oesophagus 
also. 

Each  lateral  lobe  measures  usually  two  inches  or  upwards  in  length, 
and  three-quarters  of  an  inch  in  its  thickest  part,  which  is  below  its 
middle.  The  right  lobe  is  usually  a few  lines  longer  and  thicker  than 
the  left.  The  general  direction  of  each  is,  from  below,  obliquely  up- 
wards and  backwards,  reaching  from  opposite  the  sixth  ring  of  the 
trachea  to  the  posterior  border  of  the  thyroid  cartilage,  of  which  it 
covers  the  inferior  cornu  and  adjoining  part  of  the  ala.  The  upper 
end  of  the  lobe,  which  is  thinner,  and  sometimes  called  the  cornu,  is 
usually  connected  to  the  side  of  the  thyroid  and  cricoid  cartilages  by 
cellular  tissue. 

The  transoerse  part,  or  isthmus,  which  connects  the  two  lateral 
lobes  together  a little  above  their  lower  ends,  measures  nearly  half  an 
inch  in  breadth,  and  from  a quarter  to  three  quarters  of  an  inch  in 


STRUCTURE  OF  THE  THYROID. 


141 


depth;  it  commonly  lies  across  the  third  and  fourth  rings  of  the 
trachea,  but  is  very  inconstant  in  size  and  shape,  so  that  the  portion 
of  trachea  left  uncovered  by  it  is  subject  to  corresponding  variation. 
From  the  upper  part  of  the  isthmus,  or  from  the  adjacent  portion  of 
eilher  lobe,  but  most  frequently  the  left,  a conical  portion  of  the  thy- 
roid body,  named,  from  its  shape  and  position,  the  pyramid  or  middle 
lobe  (cornu  medium,  columna  media),  often  proceeds  upwards  to  the 
middle  of  the  hyoid  bone,  to  which  its  apex  is  attached  by  loose 
fibrous  tissue.  Commonly  this  process  lies  .somewhat  to  the  left; 
occasionally  it  is  thicker  above  than  below,  or  is  completely  detached, 
or  is  split  into  two  parts.  Sometimes  it  appears  to  consist  of  fibrous 
tissue  only,  but  often  presents  a reddish  fibrous  appearance,  as  if  con- 
taining muscular  fibres.  According  to  Cruveilhier,  the  muscle  de- 
scribed by  Soemmerring,  under  the  name  of  the  levator  glandulce  thy- 
reoidecB  is  nothing  more  than  this  process  of  the  thyroid  body.  There 
can  be  no  doubt,  however,  that  in  certain  cases  true  muscular  fasci- 
culi, probably  part  of  the  thyro-hyoid  muscle,  descend  from  the  hyoid 
bone  to  the  thyroid  gland  or  its  pyramidal  process.  It  sometimes, 
though  rarely,  happens  that  the  isthmus  is  altogether  wanting,  the 
lateral  lobes  being  then  connected  by  cellular  or  fibrous  tissue  only. 

The  iveight  of  the  thyroid  body  varies  ordinarily  from  one  to  two 
ounces.  It  is  always  larger  in  the  female  than  in  the  male,  and  ap- 
pears in  the  former  to  increase  periodically  about  the  time  of  men- 
struation. The  thyroid  body,  moreover,  is  subject  to  much  variation 
of  size,  and  is,  occasionally,  the  seat  of  enormous  hypertrophy,  con- 
stituting the  disease  called  goitre.  The  colour  of  the  thyroid  body  is 
of  a dusky  brownish  red,  but  sometimes  it  presents  a yellowish  hue. 

Structure. — The  texture  of  this  organ  is  firm  and  granular.  It  is 
invested  with  a thin  transparent  layer  of  dense  cellular  tissue,  which 
connects  it  with  the  adjacent  parts,  surrounds  and  supports  the  vessels 
as  they  enter  it,  and  imperfectly  separates  its  substance  into  small 
masses  of  irregular  form  and  size.  This  interstitial  cellular  tissue  is 
free  from  fat. 

When  the  thyroid  body  is  cut  into,  a yellow  glairy  fluid  escapes 
from  the  divided  substance,  which  is  itself  found  to  consist  of  multi- 
tudes of  minute  closed  vesicles,  composed  of  a simple  external  capsular 
membrane,  and  containing  a yellow  fluid,  with  corpuscles  resembling 
cell-nuclei  and  sometimes  nucleated  cells  floating  in  it.  These  vesicles 
are  surrounded  by  capillary  vessels,  and  are  held  together  in  groups 
or  imperfect  lobules  by  areolar  tissue.  They  vary  in  size  from  gy^th 
of  an  inch  in  diameter  to  that  of  a millet-seed,  so  as  to  be  visible  to 
the  naked  eye, — differing  in  size,  however,  in  different  individuals, 
more  than  in  the  same  thyroid  body.  The  vesicles  are  spherical, 
oblong,  or  flattened,  and  are  perfectly  distinct  from  each  other ; the 
corpuscles,  according  to  Simon,*  are  in  the  foetus  and  young  subject 
disposed  in  close  apposition  and  in  a single  layer  on  the  inner  side  of 
the  vesicles,  but  detach  themselves  in  the  progress  of  growth.  The 
fluid  coagulates  by  the  action  of  heat  or  of  alcohol,  preserving,  how- 
ever, its  transparency.  According  to  the  recent  analyses,  the  sub- 
stance of  the  thyroid  body  consists  principally  of  albumen  with  traces 
* Physiological  Essay  on  the  Thymus  Gland,  Lond.  1845,  p,  78. 


142 


THE  THYMUS  GLAND. 


of  gelatine,  stearine,  oleine,  and  extractive  matter,  besides  alkaline  and 
earthy  salts  and  vrater.  The  salts  are  chloride  of  sodium,  a little 
alkaline  sulphate,  phosphates  of  potash,  lime,  and  magnesia,  with  some 
oxide  of  iron. 

Vessels. — The  arteries  of  the  thyroid  body  are  the  superior  and 
inferior  thyroids  of  each  side,  to  which  is  sometimes  added  a fifth 
vessel,  named  the  lowest  thyroid  of  Neubauer  and  Erdmann.  The 
arteries  are  remarkable  for  their  relative  size,  and  for  their  frequent 
and  large  anastomoses;  they  terminate  in  a capillary  network,  upon 
the  outside  of  the  closed  vesicles.  The  veins,  which  are  equally  large, 
ultimately  form  plexuses  on  the  surface,  from  which  a superior,  mid- 
dle, and  inferior  thyroid  vein  are  formed  on  each  side.  The  superior 
and  middle  thyroid  veins  open  into  the  internal  jugular;  the  inferior 
veins  emanate  from  a plexus  formed  in  front  of  the  trachea,  and  open 
on  the  right  side  into  the  superior  cava,  and  on  the  left  into  the  brachio- 
cephalic vein.  The  lymphatics  of  the  thyroid  body  are  extremely  nu- 
merous and  large,  and  indeed  are  supposed  to  be  concerned  in  con- 
veying into  the  blood  the  products  formed  within  this  organ. 

JM'erves. — The  nerves  are  derived  from  the  pneumogastric,  and  from 
the  middle  and  inferior  cervical  ganglia  of  the  sympathetic. 

Development. — According  to  Mr.  Goodsir,*  the  thyroid  body  is  derived  from,  or 
rather  is  a remnant  of,  the  blastodermic  or  germinal  membrane,  an  origin  which 
he  also  assigns  to  the  thymus  gland  and  suprarenal  capsules.  It  may  be  easily 
recognised,  he  says,  as  distinct  from  the  thymus  by  its  more  opaque  and  homo- 
geneous appearance,  and  by  its  containing  a larger  quantity  of  vascular  tissue 
round  its  component  cells.  According  to  the  same  observer,  the  superior  and 
inferior  thyroid  arteries  are  derived  respectively  from  the  first  and  second  primi- 
tive aortic  arches.  The  transverse  part  is  developed  subsequently  to  the  two 
lateral  lobes.  In  the  fcetus,  and  during  early  infancy,  this  organ  is  relatively 
larger  than  in  after  life ; its  proportion  to  the  weight  of  the  body  in  the  new-born 
infant  being  1 to  243  or  400,  whilst  at  the  end  of  three  weeks  it  becomes  only  1 
to  1166,  and  in  the  adult  1 to  1800.  (Krause.)  In  advanced  life  the  thyroid  body 
becomes  indurated,  and  frequently  contains  earthy  deposit;  its  vesicles  also  attain 
a very  large  size. 

THE  THYMUS  GLAND. 

The  thymus  gland  or  body  (glandula  thymus,  corpus  thymicum),  is 
a temporary  organ  which  reaches  its  greatest  size  at  about  the  end  of 
the  second  year,  after  which  period  it  ceases  to  grow,  and  is  gradually 
reduced  to  a mere  vestige.  When  examined  in  its  mature  state  in  an 
infant  under  two  years  of  age,  it  appears  as  a narrow  elongated 
glandular-looking  body,  situated  partly  in  the  thorax,  and  partly  in  the 
lower  part  of  the  neck  ; lying,  below,  in  the  anterior  mediastinal  space, 
close  behind  the  sternum,  and  in  front  of  the  great  vessels,  and  reaching 
upwards  upon  the  trachea  in  the  neck.  Its  colour  is  grayish,  with  a 
pinkish  tinge;  its  consistence  is  soft  and  pulpy,  and  its  surface  appears 
distinctly  lobulated.  It  consists  of  two  lateral  parts,  or  lobes,  which 
touch  each  other  along  the  middle  line,  and  are  nearly  symmetrical  in 
form,  though  generally  unequal  in  size,  sometimes  the  left,  and  some- 
times the  right  lobe  being  the  larger  of  the  two.  Often  an  intermediate 
lobe  exists  between  the  two  lateral  ones,  and  occasionally  the  whole 
* Philosoph.  Transact.  1846. 


STRUCTURE  OF  THE  THYMUS. 


143 


body  forms  a single  mass.  The  forms  of  the  smaller  lobules  also 
differ  on  the  two  sides. 

Each  lateral  lobe  is  of  an  elongated  triangular  form,  its  base  being 
directed  downwards.  The  summit,  or  upper  extremity,  usually  mounts 
up  into  the  neck,  reaching  above  the  sternum,  as  high  as  to  the  lower 
border  of  the  thyroid  body.  The  base  rests  on  the  upper  part  of  the 
pericardium,  to  w'hich  it  is  connected  by  cellular  tissue.  The  ante- 
rior surface,  slightly  convex,  is  covered  by  the  first  and  the  upper  part 
of  the  second  bone  of  the  sternum,  reaching,  in  the  infant  at  birth,  as 
low  down  as  opposite  the  fourth  costal  cartilage.  It  is  attached  to  the 
sternum  by  loose  cellular  tissue,  but  opposite  the  upper  part  of  that 
bone  is  separated  from  it  by  the  origins  of  the  sterno-hyoid  and  sterno- 
thyroid muscles,  which  also  cover  it  in  the  neck.  The  fosterior 
surface,  somewhat  concave,  rests,  in  the  thorax,  upon  the  front  of  the 
aortic  arch,  and  the  large  arteries  arising  from  thence,  and  also  on 
the  left  innominate  vein,  some  cellular  tissue  interposing  between  it 
and  these  parts.  In  the  neck,  it  lies  upon  the  front  and  corresponding 
side  of  the  trachea,  as  high  as  the  thyroid  body.  Its  external  border 
is  in  contact  with  the  corresponding  layer  of  the  mediastinal  pleura, 
near  the  internal  mammary  artery,  and  higher  up  (in  the  neck),  with 
the  carotid  artery,  or  its  sheath.  The  internal  border  is  in  close 
contact  with  that  of  the  opposite  lateral  lobe.  The  dimensions  of  the 
thymus  of  course  vary  according  to  its  stage  of  development.  At 
birth  it  measures  above  two  inches  in  length,  an  inch  and  a half  wide 
below,  and  about  three  or  four  lines  in  thickness.  Its  weight  at  that 
period  is  about  half  an  ounce.  Its  specific  gravity,  which  is  at  first 
about  1-050,  diminishes  as  the  gland  continues  to  waste. 

Structure. — The  thymus  gland  is  surrounded  by  a proper  invest- 
ment of  thin  areolar  tissue,  which  connects  it  with  surrounding  parts, 
and  encloses  in  a common  envelope  the  smaller  masses  which  com- 
pose it.  This  being  removed,  the  substance  of  the  thymus  is  found  to 
consist  of  numerous  compressed  lobules,  connected  by  a more  delicate 
intervening  areolar  tissue.  These  lobules  vary  in  size  from  that  of  a 
pin’s  head  to  that  of  a pea.  Each  lobule,  when  divided,  is  seen  to 
contain  several  membranous  cells  or  vesicles.  According  to  Sir  Astley 
Cooper,*  the  cellular  recesses  of  each  lobule  open  into  a small  pouch 
at  its  base,  which  in  turn  communicates  with  a large  elongated  central 
cavity  running  through  the  corresponding  lateral  lobes  of  the  gland — 
the  vesicles,  the  pouches,  and  the  central  cavity,  all  containing  a 
white  fluid  resembling  chyle.  This  cavity,  named  by  Sir  A.  Cooper 
the  reservoir  of  the  thymus,  is  represented  by  him  as  branching  out 
into  diverticula,  around  which  the  lobules  are  disposed,  and  is  de- 
scribed as  being  lined  by  a vascular  membrane,  which  is  prolonged 
through  the  diverticula  and  pouches  into  the  cells.  Moreover,  the 
lobules  themselves  are  said  to  be  held  together  by  a strong  band, 
around  which  they  are  attached  like  knots  upon  a rope,  which  is  itself 
arranged  spirally  around  the  common  central  cavity.  The  existence 
of  a continuous  central  cavity,  containing  a ch}dous  fluid,  is  doubted 
by  Henie,  and  denied  by  Berres,  Bischoff,  and  Haugstedt,  who  think 
that  the  vesicles  are  perfectly  closed,  and  independent  of  each  other. 

• Anatomy  of  the  Thymus  Gland.  London,  1832. 


144 


STRUCTURE  OF  THE  THYMUS. 


Mr.  Goodsir  is  of  opinion  that  this  common  cavity  results  from  the 
mode  of  preparation,  by  the  distension  and  separation  of  contiguous 
lobules  M'hich  adhere  only  slightly  together,  whilst  the  entire  glandular 
mass  is  enveloped  in  a strong  cellular  capsule.  Meckel,  Tiedemann, 
and  Huschke  recognise  the  presence  of  a cavity,  which,  according  to 
the  latter,  is  most  distinctly  seen  in  well-nourished  children,  in  whom 
it  is  distended  with  a white  fluid.  Mr.  Simon,  who  by  his  recent 
investigations  has  shown  that  the  primitive  form  of  the  thymus  gland 
is  a linear  tube,  from  which,  as  it  grows,  lateral  branched  diverticula 
subsequently  bud  out,  states,  that  in  the  mature  thymus,  this  tube 
becomes  obscure;  that  the  central  cavity  described  and  figured  by 
Sir  A.  Cooper  is  too  large,  owing  to  over-distension;  but,  nevertheless, 
that  all  the  parts  of  each  lateral  lobe  of  the  thymus  do  depend  on  a 
single  common  cavity,  and  that  even  the  terminal  vesicles  communi- 
cate with  it  by  means  of  the  numerous  diverticula.  The  central 
cavity  has  no  outlet,  and  the  thymus  gland  has  no  excretory  duct. 

The  walls  of  the  ultimate  vesicles  are  formed  of  simple  homo- 
geneous membrane;  they  are  surrounded  by  a network  of  fine  capil- 
lary vessels,  and  are  supported  by  a delicate  cellular  tissue,  containing 
some  elastic  fibres.  The  white  fluid  found  in  the  vesicles  and  interior 
of  the  thymus  is  particularly  abundant  in  stout  healthy  infants,  but 
scanty  in  opposite  conditions.  It  contains  numerous  corpuscles, 
closely  resembling  the  pale  blood-corpuscles  and  those  found  in  the 
chyle  and  in  the  juice  of  the  lymphatic  glands.  The  milky  character 
of  the  thymic  fluid  is  owing  to  the  presence  of  these  corpuscles,  and 
not  of  minute  molecules  as  is  the  case  with  the  chyle.  The  corpuscles 
are  either  flattened  circular  discs  or  spherical  bodies,  varying  in  dia- 
meter from  to  -si/soth  of  an  inch.  They  contain  a nucleus, 

composed  itself  of  from  one  to  three,  or  even  four,  dark  clear  granules. 
According  to  the  observations  of  Mr.  Gulliver,  the  action  of  reagents 
upon  the  corpuscles  of  the  fluid  of  the  thymus  is  precisely  similar  to 
that  upon  the  corpuscles  of  the  chyle  and  lymph. 

Vessels. — The  arteries  are  derived  from  various  sources,  viz.,  from 
the  internal  mammary  arteries,  the  inferior  and  superior  thyroid,  the 
subclavian  and  carotid  arteries.  They  terminate  in  capillary  vessels, 
which  form  a vascular  envelope  around  each  vesicle. 

The  veins  pursue  a different  course  from  the  arteries,  and,  for  the 
most  part,  open  into  the  left  innominate  vein. 

The  lymphatics  are  large,  but  their  course  has  not  been  well  studied. 
Sir  A.  Cooper  succeeded  in  injecting  them  only  once  in  the  human 
subject.  According  to  Simon,  they  may  be  traced  through  the  gland, 
but  do  not  arise  from  its  cavity;  they  terminate  in  the  thoracic  duct, 
or  in  the  right  lymphatic  duct.  It  is  probable  that  they  are  concerned 
in  conveying  into  the  blood  the  products  formed  in  the  substance  of 
the  thymus. 

The  nerves  are  very  minute.  Haller  thought  they  were  partly  de- 
rived from  the  phrenic  nerves,  but,  according  to  Sir  A.  Cooper,  no 
filaments  from  these  nerves  go  into  the  gland,  though,  as  well  as  a 
branch  from  the  descendens  noni,  they  reach  the  investing  capsule. 
Small  filaments,  derived  from  the  pneumogastric  and  sympathetic 
nerves,  descend  on  the  thyroid  body,  to  the  upper  part  of  the  thymus. 


DEVELOPMENT  OF  THE  THYMUS. 


145 


Sympathetic  nerves  also  reach  the  gland  along  its  various  arteries, 
especially  on  the  thymic  branch  of  the  internal  mammary  artery. 

Chemical  Composition. — The  substance  and  fluid  of  the  thymus  con- 
tain nearly  eighty  per  cent,  of  water.  Its  solid  animal  constituents 
are  composed  essentially  of  albumen  and  fibrin  in  large  quantities, 
mixed  with  gelatine  and  other  animal  matter.  The  salts  are  princi- 
pally alkaline  and  earthy  phosphates,  with  chloride  of  potassium.  It 
contains,  therefore,  no  constituents  especially  rich  in  carbon. 

Development. — According  to  Mr.  Goodsir,*  the  thymus  gland,  like  the  thyroid 
body,  is  essentially  a highly-developed  remnant  of  the  blastodermic  membrane, 
the  use  of  which,  both  originally  and  as  thus  modified,  he  conceives  to  be  to  pre- 
pare material  for  nutritive  purposes.  At  first,  according  to  his  statement,  the  thy- 
roid and  thymus  are  not  distinguishable  from  each  other,  but  soon  they  become 
separated  by  the  absorption  of  a part  between  them. 

The  early  development  of  the  thymus  has  been  carefully  studied  by  Mr. 
Simon,!  whose  researches  were  chiefly  conducted  in  the  embryos  of  swine  and 
oxen.  In  embryos,  about  half  an  inch  in  length,  it  may  be  seen  by  the  aid  of  a 
high  power;  and  in  those  of  one  and  a half  inch,  by* the  aid  of  a simple  lens. 
When  first  distinguishable,  it  consists  of  a simple  tube  closed  in  all  directions, 
lying  along  the  carotid  vessels.  The  contents  of  this  tube  are  granular,  but  do 
not  show  regular  corpuscles;  its  wails  are  delicate  and  homogeneous.  The  tube 
has  no  connexion  with  the  respiratory  mucous  membrane,  as  was  supposed  by 
Arnold ; and,  so  soon  as  it  is  discoverable,  it  is  found  to  be  perfectly  distinct 
from  the  thyroid  body.  At  intervals  along  the  sides  of  this  tube  small  vesicles 
bud  out,  so- as  to  form  lateral  diverticula,  which  contain  nucleated  corpuscles, 
and  which  go  on  subsequently  branching  out  by  twos  or  fours, — the  formation  of 
the  permanent  vesicles  being  merely  the  last  repetition  of  this  process.  In  the 
human  fostus,  at  about  the  ninth  week  the  thymus  consists  of  two  minute 
elongated  parallel  parts,  lying  chiefly  on  the  upper  part  of  the  pericardium,  and 
presenting  under  the  microscope  a distinct  tubulo-vesicular  structure  ; it  then  in- 
creases rapidly  until  birth,  but  not  equally,  for  it  grows  especially  during  the 
seventh,  eighth,  and  ninth  months  of  intra-uterine  existence. 

After  birth,  the  thymus,  as  already  stated,  continues  to  grow  to  near  the  end  of 
the  second  year.  According  to  the  observations  of  Haugstedt  and  Simon  upon 
the  weight  of  this  organ  in  young  animals,  it  appears  for  a short  time  after  birth 
to  increase  not  merely  absolutely,  but  even  faster  than  the  rest  of  the  system,  and 
during  the  next  period  only  to  keep  pace  with  the  increase  of  the  body.  After 
the  second  year  it  ceases  to  grow,  and  becomes  gradually  converted  by  the 
eighth  or  twelfth  year  into  a fatty  mass.  In  this  condition  the  corpuscles  of  the 
thymus  disappear,  forming,  accordmg  to  Simon’s  opinion,  the  nuclei  of  cells 
which  become  developed  into  the  cells  of  adipose  tissue.  At  puberty  the  thymus 
is  reduced  to  a mere  vestige,  losing  its  original  structure  entirely,  and  consisting 
of  brownish  tissue  found  in  the  upper  part  of  the  anterior  mediastinum.  Traces 
of  it,  however,  have  been  found  at  the  twentieth  or  twenty-fifth  year,  and,  as  an 
extreme  exception,  at  the  age  of  thirty. 

The  thymus  gland  presents  no  difference  in  the  two  sexes.  It  exists,  according 
to  Simon,  in  all  animals  breathing  by  lungs,  and  is  persistent  in  those  which 
hibernate,  though  only  as  a mass  of  fat. 

Function. — ^The  functions  of  the  thymus  gland  are  not  known.  It  was  sup- 
posed by  Hewson,  on  the  ground  of  the  identity  between  the  thymic  and  lymph 
particles,  that  this  organ  is  an  appendage  to  the  lymphatic  system,  and  that  its 
particles  are  concerned  in  the  formation  of  the  blood  globules.  Others  have  con- 
ceived that  its  office  was  in  some  way  to  prepare  a nutritive  fluid  for  the  system 
of  the  foetus  and  early  infant.  Mr.  Simon  concludes,  that  the  thymus  is  intended 
to  set  aside  from  the  blood  a reserve  of  oxidizable  material  available  for  respira- 
tion, at  a period  of  life  when  but  a scanty  supply  of  respirable  matter  is  derived 
from  the  wear  of  the  muscular  tissue. 

* Loc.  cit.  Philos.  Trans.  1846. 

13 


VOL.  II. 


t Op.  cit. 


NEUROLOGY. 


NERVOUS  SYSTEM. 

Of  the  functions  performed  through  the  agency  of  the  nervous  sys- 
tem, some  are  entirely  corporeal,  whilst  others  involve  phenomena  of 
a mental  or  psychical  nature.  In  the  latter  and  higher  class  of  such 
functions  are  first  to  Ke  reckoned  those  purely  intellectual  operations, 
carried  on  through  the  instrumentality  of  the  brain,  w'hich  do  not 
immediately  arise  from  an  external  stimulus,  and  do  not  manifest 
themselves  in  outward  acts.  To  this  class  also  belong  sensation  and 
volition.  In  the  exercise  of  sensation  the  mind  becomes  conscious, 
through  the  medium  of  the  brain,  of  impressions  conducted  or  propa- 
gated to  that  organ  along  the  nerves  from  distant  parts;  and  in  volun- 
tary motion  a stimulus  to  action  arises  in  the  brain,  and  is  carried 
outwards  by  the  nerves  from  the  central  organ  to  the  voluntary  mus- 
cles. Lastly,  emotion,  which  gives  rise  to  gestures  and  movements 
varying  with  the  different  mental  affections  which  they  express,  is  an 
involuntary  state  of  the  mind,  connected  with  some  part  of  the  brain, 
and  influencing  the  muscles  through  the  medium  of  the  nerves. 

The  remaining  functions  of  the  nervous  system  do  not  necessarily 
imply  any  participation  of  the  mind.  In  the  production  of  those 
movements,  termed  rejlex,  excited,  or  excito-motory,  a stimulus  is  car- 
ried along  afferent  nerve-fibres  to  the  brain,  or  spinal  cord,  and  is 
then  transferred  to  efferent  or  motor  nerve-fibres,  through  which  the 
muscles  are  excited  to  action ; and  this  takes  place  quite  indepen- 
dently of  the  will,  and  may  occur  without  consciousness.  The 
motions  of  the  heart,  and  of  other  internal  organs,  as  well  as  the  in- 
visible changes  which  occur  in  secretion  and  nutrition,  are  in  a cer- 
tain degree  subject  to  the  influence  of  the  nervous  system,  and  are 
undoubtedly  capable  of  being  modified  through  its  agency,  though, 
with  regard  to  som^  of  these  phenomena,  it  is  doubtful  how  far  the 
direct  intervention  of  the  nervous  system  is  necessary  for  their  pro- 
duction. These  actions,  which  are  all  strictly  involuntary,  are,  no 
doubt,  readily  influenced  by  mental  emotions;  but  they  may  also  be 
affected  through  the  nerves,  in  circumstances  which  entirely  preclude 
the  participation  of  the  mind. 

The  nervous  system  consists  of  a central  part,ov  rather  a series  of 
connected  central  organs,  named  the  cerebrospinal  axis,  or  cerebro- 
spinal centre  ; and  of  the  nerves,  which  have  the  form  of  cords  con- 
nected by  one  extremity  with  the  cerebro-spinal  centre,  and  extending 


NERVOUS  SYSTEM. 


147 


from  thence  through  the  body  to  the  muscles,  sensible  parts,  and 
other  organs  placed  under  their  control.  The  nerves  form  the  medium 
of  communication  between  these  distant  parts  and  the  centre ; one 
class  of  nervous  fibres,  termed  afferent  or  centripetal,  conducting  im- 
pressions towards  the  centre, — another,  the  efferent  or  centrifugal, 
carrying  motorial  stimuli  from  the  centre  to  the  moving  organs.  The 
nerves  are,  therefore,  said  to  be  internuncial  in  their  office,  whilst  the 
central  organ  receives  the  impressions  conducted  to  it  by  the  one 
class  of  nerves,  and  imparts  stimuli  to  the  other, — rendering  certain  of 
these  impressions  cognizable  to  the  mind,  and  combining  in  due*  asso- 
ciation, and  towards  a different  end,  movements,  whether  voluntary 
or  involuntary,  of  different,  and  often  of  distant  parts. 

Besides  the  cerebro-spinal  centre  and  the  nervous  cords,  the  nervous 
system  comprehends  also  certain  bodies  named  ganglia,  which  are 
connected  with  the  nerves  in  various  situations.  These  bodies,  though 
of  much  smaller  size  and  less  complex  nature  than  the  brain,  agree, 
nevertheless,  with  that  organ  in  their  elementary  structure,  and  to  a 
certain  extent  also  in  their  relation  to  the  nervous  fibres  with  which 
they  are  connected ; and  this  correspondence  becomes  even  more 
apparent  in  the  nervous  system  of  the  lower  members  of  th”e  animal 
series.  For  these  reasons,  as  well  as  from  evidence  derived  from  ex- 
periment, but  which  as  yet,  it  must  be  confessed,  is  of  a less  cogent 
character,  the  ganglia  are  regarded  by  many  as  nervous  centres,  to 
which  impressions  may  be  referred,  and  from  which  motorial  stimuli 
may  be  reflected  or  emitted ; but  of  local  and  limited  influence  as 
compared  with  the  cerebro-spinal  centre,  and  operating  without  our 
consciousness  and  without  the  intervention  of  the  will. 

The  nerves  are  divided  into  the  cerebro-spinal,  and  the  sympathetic 
or  ganglionic  nerves.  The  former  are  distributed  principally  to  the 
skin,  the  organs  of  the  senses,  and  other  parts  endowed  with  manifest 
sensibility,  and  to  muscles  placed  more  or  less  under  the  control  of  the 
will.  They  are  attached  in  pairs  to  the  cerebro-spinal  axis,  and  like 
the  parts  which  they  supply  are,  with  few  exceptions,  remarkably 
symmetrical  on  the  two  sides  of  the  body.  The  sympathetic  or  gan- 
glionic nerves,  on  the  other  hand,  are  destined  chiefly  for  the  viscera 
and  blood-vessels,  of  which  the  motions  are  involuntary,  and  the 
natural  sensibility  is  obtuse.  They  differ  also  from  the  cerebro-spinal 
nerves  in  having  generally  a grayish  or  reddish  colour,  in  their  less 
symmetricail  arrangement,  and  especially  in  the  circumstance  that  the 
ganglia  connected  with  them  are  much  more  numerous  and  more 
generally  distributed.  Branches  of  communication  pass  from  the 
spinal  and  several  of  the  cerebral  nerves  at  a short  distance  from  their 
roots,  to  join  the  sympathetic,  and  in  these  communications  the  two 
systems  of  nerves  mutually  give  and  receive  nervous  fibres. 

The  nervous  system  is  made  up  of  a substance  proper  and  peculiar 
to  it,  with  inclosing  membranes,  cellular  tissue,  and  blood-vessels.  The 
nervous  substance  has  been  long  distinguished  into  two  kinds,  obvi- 
ously differing  from  each  other  in  colour,  and  therefore  named  the 
white,  and  the  gray  or  cineritious. 


148 


NERVOUS  SYSTEM. 


CHEMICAL  COMPOSITION. 

The  information  we  possess  respecting  the  chemical  composition  of 
nervous  matter  is  for  the  most  part  founded  on  analyses  of  portions  of 
the  brain  and  spinal  cord  ; but  the  substance  contained  in  the  nerves, 
which  is  continuous  with  that  of  the  brain  and  cord,  and  similar  in 
physical  characters,  appears  also,  as  far  as  it  has  been  examined,  to 
be  of  the  same  general  chemical  constitution.  No  very  careful  com- 
parative analysis  has  yet  been  made  of  the  gray  and  white  matter,  to 
say  nothing  of  the  different  structural  elements  of  the  nervous  sub- 
stance ; and  indeed  it  must  be  remembered,  that,  in  portions  of  brain 
subjected  to  chemical  examination,  capillary  blood-vessels,  and  per- 
haps other  accessory  tissues,  are  mixed  up  in  greater  or  less  quantity 
with  the  true  nervous  matter,  and  must  so  far  affect  the  result. 

The  nervous  matter  may  be  said  to  consist  of  albumen  dissolved  in 
water,  and  combined  with  fatty  principles  and  salts.  The  water, 
which  forms  four-fifths  of  the  whole  cerebral  substance,  may  be  re- 
moved by  immersion  in  alcohol  and  evaporation.  When  the  solid 
matter  which  remains,  after  removal  of  the  water,  is  treated  with 
ether  and  hot  alcohol,  the  fatty  compounds  are  extracted  from  it  by 
these  menstrua,  and  there  remains  a mixture  of  coagulated  albumen 
and  salts  with  a small  amount  of  accessory  tissues,  chiefly  vessels. 

According  to  Vauquelin,  the  human  brain  contains  in  one  hundred  parts,  water, 
80,  albumen  7,  white  fat  4 55,  red  fat  0 7,  osmazome  1'12,  phosphorus  15,  acids, 
salts,  and  sulphur  5-15.  Of  the  fat,  cholesterine,  the  properties  of  which  have 
been  already  stated,  vol.  i.  p.  48,  forms  a large  part.  The  remainder  may,  accord- 
ing to  Couerbe,  be  resolved  into,  1.  Cerehrot,  an  unsaponifiable  and  difficultly  fu- 
sible fat  like  cholesterine;  2.  Eleencephol,  a reddish  oil  which  readily  dissolves  the 
other  cerebral  fats;  3.  Cephalot;  and  4.  Stearo-conot,  two  solid  saponifiable  fats  of 
a yellow  colour,  differing  in  fijsibility,  and  in  their  solubility  in  ether.  Couerbe 
states,  that  these  four  fatty  compounds  contain,  in  addition  to  the  usual  elements 
of  such  substances,  also  nitrogen,  sulphur,  and  phosphorus. 

Fremy,  who  has  since  investigated  the  subject,  represents  the  cerebral  substance 
as  consisting  of  80  per  cent,  of  water,  7 of  albumen,  and  5 of  fatty  constituents. 
These  last  are,  1.  Cerebric  acid,  which  is  the  most  abundant;  2.  Cholesterine ; 3. 
Oleophosphoric  acid;  and  4.  Olein,  Margarin,  and  traces  of  their  acids.  The  pro- 
perties of  most  of  these  fats  have  been  already  noticed  (vol.  i.p.  47).  Fremy  de- 
nies that  they  contain  sulphur  as  a constituent,  and  he  ascribes  the  presence  of 
that  ingredient  to  an  admixture  of  albumen.  He  finds  that  the  oleophosphoric 
acid  is  a very  unstable  compound,  and  that  under  the  inlluence  of  slight  causes 
it  is  readily  transformed  into  phosphoric  acid  and  olein.  According  to  the  same 
inquirer,  the  fat  contained  in  the  brain  is  confined  almost  entirely  to  its  white 
substance,  which  loses  its  characteristic  white  aspect  when  the  fat  has  been  e.x- 
tracted.  The  spinal  cord  and  nerves  yield  the  same  constituents  as  the  brain ; 
but  the  cord  is  said  by  Vauquelin  to  contain  a larger  proportion  of  fat;  and,  ac- 
cording to  L’Heritier,  the  nerves  contain  more  albumen,  and  less  of  solid,  but 
more  of  soft  fat,  than  the  brain. 

STRUCTURAL  ELEMENTS. 

When  subjected  to  the  microscope,  the  nervous  substance  is  seen  to 
consist  of  two  different  structural  elements,  viz.,  fibres,  and  cells  or 
vesicles.  The  fibres  are  found  universally  in  the  nervous  cords,  and 
they  also  constitute  the  greater  part  of  the  nervous  centres ; the  cells 
or  vesicles  on  the  other  hand  are  confined  in  a great  measure  to  the 
latter,  and  do  not  exist  in  the  nerves  properly  so  called,  unless  it  be  at 


STRUCTURAL  ELEMENTS. 


149 


their  peripheral  expansions  of  some  of  the  organs  of  special  sense ; 
they  are  contained  in  the  gray  portion  of  the  brain,  spinal  cord,  and 
ganglia,  which  gray  substance  is  in  fact  made  up  of  these  vesicles  in- 
termixed in  many  parts  wdth  fibres,  and  with  a variable  quantity  of 
granular  or  amorphous  matter. 

In  further  pursuing  the  subject,  we  shall  first  examine  the  fibres  and 
vesicles  by  themselves,  and  afterwards  consider  the  structure  of  the 
parts  which  they  contribute  to  form,  viz.,  the  cerebro-spinal  organs, 
the  ganglia,  and  the  nerves. 

The  fibres  are  of  two  kinds : the  tubular  or  ivhite,  and  the  gelatinous 
or  gray ; the  former  are  by  far  the  most  abundant ; the  latter  are  found 

Fig.  311. 


A.  Tubular  nerve-fibres,  showing  the  sinuous  outline  and  double  contours. 

B.  Diagram  to  show  the  parts  of  a tubular  fibre,  viz.,  1,  I,  membranous  tube.  2,  2,  while  sub- 
stance or  medullary  sheath.  3.  axis  or  primitive  band. 

c.  Figure  (imaginary)  intended  to  represent  the  appearances  occasionally  seen  in  the  tubular 
fibres.  1,  1,  membrane  of  the  tube  seen  at  parts  where  the  white  substance  has  separated  from 
it.  2,  a part  where  the  white  substance  is  interrupted.  3,  axis  projecting  beyond  the  broken 
end  of  the  tube.  4,  part  of  the  contents  of  the  tube  escaped. 

principally  in  the  sympathetic  nerve,  but  are  known  to  exist  also  in 
many  of  the  cerebro-spinal  nerves. 

The  Tubular  Fibres.* — These  form  the  white  part  of  the  brain, 
spinal  cord,  and  nerves.  When  collected  in  considerable  numbers, 
and  seen  with  reflected  light,  the  mass  which  they  form  is  white  and 
opaque.  Viewed  singly,  or  few  together,  under  the  microscope,  with 
transmitted  light,  they  are  transparent;  and  if  quite  fresh  from  a newly 
killed  animal,  and  unchanged  by  cold  or  exposure,  they  appear  as  if 
entirely  homogeneous  in  substance,  like  threads  of  glass,  and  are 

* Also  named  “ white  fibres”  and  ” nerve  tubules I prefer  the  term  “ tubular  fibres  ** 
first  used,  so  far  as  I know,  by  Dr.  Todd. 


13* 


150 


NERVOUS  SYSTEM. 


bounded  on  each  side  by  a simple  and  usually  gently  sinuous  outline. 
Their  size  differs  considerably  even  in  the  same  nerve,  but  much  more 
in  different  parts  of  the  nervous  system;  some  being  as  small  as  the 
Ts’oBO  others  upwards  of  the  of  an  inch  in  diameter;  and  the 
same  fibre  may  change  its  size  in  different  parts  of  its  course.  Very 
speedily  after  death,  and  especially  on  e'xposure  to  the  action  of  water, 
these  seemingly  homogeneous  fibres  become  altered ; and  it  is  when 
so  altered  that  they  are  commonly  subjected  to  examination,  as  repre- 
sented in  fig.  311,  A.  In  particular  instances,  and  in  favourable  cir- 
cumstances, it  may  be  discovered  that  the  fibre  is  composed  of  a fine 
membranous  tube,  enclosing  a peculiar  soft  substance,  and  that  this 
contained  substance  itself  is  distinguishable  into  a central  part  placed 
like  a sort  of  axis  in  the  middle  of  the  tube,  and  a peripheral  portion 
surrounding  the  axis,  and  occupying  the  space  between  it  and  the  tu- 
bular inclosing  membrane.  In  the  annexed  ideal  plan,  (fig.  311,b,) 
the  membranous  tube  is  marked  1,1:  the  central  part,  marked  3,  was 
named  cylinder  axis  by  Purkinje,  who  considered  it  to  be  identical 
with  the  structure  previously  described  by  Remak  under  the  name  of  the 
'primitive  band  (fibra  primitiva) ; the  matter  surrounding  it,  marked  2, 
2,  is  supposed  to  be  the  chief  cause  of  the  whiteness  of  the  brain  and 
nerves,  and  it  was  accordingly  named  the  white  substance  by  Schwann, 
and  by  others,  though  less  appropriately,  the  medullary  sheath.  It  is 
this  last-mentioned  substance  which  undergoes  the  most  marked  change 
on  exposure  ; it  then  seems  to  suffer  a sort  of  coagulation  or  congelation, 
and,  when  this  has  taken  place,  it  very  strongly  refracts  the  light,  and 
gives  rise  to  the  appearance  of  a shaded  border  on  each  side  of  the 
nerve-tube  (fig.  311,  a and  c).  This  border,  though  darker  than  the 
rest  of  the  tube,  is  nevertheless  translucent,  and  is  either  colourless,  or 
appears  of  a slightly  yellowish  or  brownish  tint;  it  is  bounded  by  two 
nearly  parallel  lines,  so  that  the  nerve-fibre  has  then  a double  contour, 
and  the  inner  line  gradually  advances  further  inwards  as  the  change 
in  the  white  substance  extends  to  a greater  depth.  These  parallel 
lines  pursue  a sinuous  course,  often  with  deep  and  irregular  indenta- 
tions : while  straight  or  curved  lines  of  the  same  character,  occasioned 
no  doubt  by  wrinkles  or  creases  in  the  layer  of  white  substance,  are 
frequently  seen  crossing  the  tube.  By  continued  exposure,  round  and 
irregular  spots  appear  at  various  points,  and  at  length  the  contents  of 
the  nerve-tube  acquire  a confusedly  granular  aspect. 

The  double  contour  appears  only  in  fibres  of  a certain  size;  in  very  fine  tubes, 
which  become  varicose  or  dilated  at  intervals,  the  double  line  is  seen  only  in  the 
enlargements,  and  not  in  the  narrow  parts  between.  It  often  happens  that  the 
soft  contents  of  the  tube  are  pressed  out  at  the  ruptured  extremities,  as  in  fig.  311, 
c 4,  and  then  the  round  or  irregular  masses  of  the  effused  matter  are  stiU  sur- 
rounded by  the  double  line,  which  proves  that  this  appearance  is  produced  inde- 
pendently of  the  membranous  tube.  So  long  as  this  tube  is  accurately  filled  by 
the  contained  matter,  its  outline  cannot  be  distinguished;  but  sometimes,  when 
the  white  substance  separates  at  various  points  from  the  inside  of  the  tube,  the 
contour  of  the  fibre  becomes  indented  and  irregular,  and  then  the  membrane  of 
the  tube  may,  in  favourable  circumstances,  be  discerned  as  an  e.xtremely  faint 
line,  running  outside  the  deeply  shaded  border  formed  by  the  white  substance, 
and  taking  no  part  in  its  irregular  sinuosities  (fig.  311,  c,  1,  1).  The  membranous 
tube  may  also  be  distinguished  at  parts  where  the  continuity  of  its  contained 


TUBULAR  FIBRES. 


I5I 


"matter  is  broken  in  consequence  of  traction,  squeezing,  or  such  like  injury  of  the 
fibre;  in  such  parts  the  double  line  produced  by  the  white  substance  is  wanting, 
and  the  faint  outline  of  the  membranous  tube  maybe  perceived  passing  over  the 
interruption  (2).  The  fine  transparent  membrane  which  forms  this  tube  appears 
to  be  quite  simple  and  homogeneous  in  structure. 

The  axis  is  situated  in,  or  near,  the  middle  of  the  nerve-tube,  where 
it  may  occasionally  be  seen,  on  a careful  inspection,  as  a transparent 
stripe  or  band,  bounded  on  either  side  by  a very  faint  even  outline, 
having  no  share  in  the  sinuosities  of  the  white  substance  (fig.  311,  c). 


The  axis  seems  to  be  of  a more  tenacious  consistence  than  the  white  substance, 
and  may  accordingly  be  sometimes  seen  projecting  beyond  it  at  the  end  of  a 
broken  nerve-tube,  either  quite  denuded,  or  covered  only  by  the  tubular  mem- 
brane, the  intervening  white  substance  having  escaped.  Although  the  name  of 
axis  cylinder  would  seem  to  imply  that  it  had  actually  a cylindrical  figure,  yet 
this  is  by  no  means  certain ; and  whether  naturally  cylindrical  or  not,  it  certainly 
very  generally  appears  more  or  less  flattened  when  subjected  to  examination. 
One  writer  (Hannover*)  is  inclined  to  think  that  it  is  hollow,  and  that  it  collapses 
into  a flat  band  when  exposed;  but  this  is  not  probable.  It  sometimes  appears 
striated  longitudinally,  and  it  has  been  observed  even  to  split  into  finer  filaments. 
Others  have  conceived  that  the  soft  matter  contained 
in  the  nerve-tube  is  of  uniform  nature  throughout, 
and  that  the  axis  is  nothing  more  than  a portion 
of  this  substance  in  the  centre,  which  has  remained 
unchanged  whilst  the  superficial  and  more  exposed 
part  has  become  coagulated;  a supposition  difficult 
to  reconcile  with  the  fact  that  the  axis  often  appears 
more  consistent,  at  least  more  tenacious,  than  the  en- 
veloping white  substance.  It  seems  on  the  whole 
more  probable  that  there  is  an  original  difference  of 
material  between  the  central  and  peripheral  part  of 
the  nerve-pulp,  and  that  the  effect  of  exposure  is  to 
render  the  difference  more  conspicuous.  The  nerve- 
pulp,  as  already  stated,  is  in  its  chemical  constitution 
an  oleo-albuminous  compound ; and  there  seems 
some  reason  to  think  that  the  oleaginous  constituent 
is  represented  entirely  by  the  white  substance;  for 
whilst  water,  especially  when  cold,  rapidly  produces 
congelation  of  that  substance,  [fig.  312,  a,]  ether  on 
the  other  hand  causes  it  speedily  to  disappear  as  if 
by  solution,  and  globules  of  oil  afterwards  make  their  eel;— a.  In  water.  The  delicate 
appearance  both  within  and  without  the  tube,  its  re-  , 'If  exterior  in^caies  the 
maining  contents  becoming  granular  [fig.  312,  b}.  dtubk-edtltd  giner  on/ia‘^Tt!e 

Many  of  the  tubular  nerve-fibres,  when  sub-  .iStVSS. 
jected  to  the  microscope,appeardilatedor swol-  m ether.  Several  oii-giobuies 
len  out  at  short  distances  along  their  length,  and  accumS 

contracted  in  the  intervals  between  the  dilated  around  the  exterior  of  the  tube, 
parts.  Such  fibres  have  been  named  varicose  JXpeared.“-XTgn^^ 

(fig.  313).  They  occur  principally  in  the  ameters.— Todd  and  Bowman.] 
brain  and  spinal  cord,  and  in  the  intracranial  part  of  the  olfactory,  in 
the  optic,  and  acoustic  nerves ; they  are  occasionally  met  with  also 
m the  other  nerves,  especially  in  young  animals.  These  fibres,  how- 
ever, are  naturally  cylindrical  like  the  rest,  and  continue  so  while  they 
remain  undisturbed  in  their  place;  and  the  varicose  character  is  occa- 
sioned by  pressure  or  traction  during  the  manipulation,  which  causes 

* Recherches  microscopiques  sur  le  Syst^me  Nerveux,  1844,  p, 


Nerve-tubes  of  the  common 


152 


NERVOUS  SYSTEM. 


the  soft  matter  contained  in  the  nerve-tube  to  accumulate  at  certain 
p.  gjg  points,  while  it  is  drawn  out  and  attenuat- 

' ed  at  others.  Most  probably  the  change 

takes  place  before  the  nerve-pulp  has  coa- 
gulated. The  fibres  in  which  it  is  most 
apt  to  occur  are  usually  of  small  size, 
ranging  from  to  of  an  inch 

in  diameter ; and  when  a very  small 
fibre  is  thus  aflected,  the  varicosities 
appear  like  a string  of  globules  held 
together  by  a fine  transparent  thread. 
As  already  remarked,  the  double  con- 
tour caused  by  congelation  of  the  white 
substance  does  not  appear  in  the  highly 
constricted  parts.  Hannover  states  that 
the  axis  may  sometimes  be  seen  running 
through  the  varicosities  and  undergoing 
no  corresponding  dilatation. 

Neither  in  their  course  along  the  ner- 
vous cords,  nor  in  the  nervous  centres, 
have  these  tubular  fibres  ever  been  ob- 
served to  unite  or  anastomose  together, 
nor  are  they  seen  to  divide  into 
Fibresfrom  the  root  of  aspinal  nerve,  bi-jinches  ; it  is  therefore  fair  to  con- 

At  0,  where  they  join  the  spinal  cord,  i j .i  . .1  11  j • 1 

they  are  varicose  ; lower  down,  at  a,  clude  that,  thoUgh  bound  Up  m numbers 

they  are  uniform  and  larger.— (Vat-  jn  the  same  nervous  cords,  they  merely 

run  side  by  side  like  the  threads  in  a 

skein  of  silk,  and  that  they  maintain  their  individual  distinctness  from 

one  end  to  the  other.  They,  however,  divide  in  some  cases  at  their 

peripheral  terminations. 

Of  the  Gelatinous  Fibres. — These,  which  have  also  been  named 
“ organic”  or  “ gray”  nerve-fibres  (fig.  314),  exist  in  great  numbers  in 
the  sympathetic  nerve,  and  are  also  found  in  many  of  the  cerebro- 
spinal nerves,  but  for  the  most  part  in  much  smaller  proportion.  In 

both  cases  they  are  associated  with 
tubular  or  white  fibres,  and  they  give 
a gray  colour  to  those  nervous  cords 
in  which  they  predominate.  There  is 
some  doubt  as  to  the  real  nature  of 
these  gelatinous  fibres ; several  anato- 
mists, whose  opinion  is  deservedly  held 
in  high  estimation,  denying  that  they 
are  true  nerve-fibres,  and  maintaining 
that  they  belong  to  the  class  of  enve- 
loping structures,  and  are  allied  in 
nature  and  office  to  the  fibres  of  cellu- 
lar tissue.  In  their  microscopic  cha- 
racters they  bear  a strong  resemblance 
to  the  plain  muscular  fibres,  but  are  of 
smaller  average  breadth,  their  diameter  measuring  from  to 


Fig.  314. 


Gelatinous  nerve-fibres,  (a  and  b mag- 
nified 340  diameters,  after  Hannover;  c 
and  d after  Remak.) 


NERVE-CELLS  OR  NERVE-VESICLES. 


153 


of  an  inch.  They  are  flattened,  translucent,  and  apparently  homo- 
geneous, or  at  most  faihtly  granular,  with  numerous  corpuscles 
resembling  cell-nuclei  lying  on  them.  Of  these  nuclei  some  are  round, 
and  many  oval  or  fusiform,  lying  with  their  long  diameter  in  the 
direction  of  the  fibres ; many  contain  one  or  more  nucleoli.  These 
fibres  seem  to  be  of  rather  tenacious  consistence,  and  are  difficult  to 
separate  from  one  another;  some  observers  describe  them  as  being 
sometimes  split  at  their  ends  into  smaller  filaments. 

N'erve-ceUs  or  JVerve-vesicles. — These,  as  already  mentioned,  consti- 
tute the  second  kind  of  structural  elements  proper  to  the  nervous 
system.  They  are  found  in  the  gray  matter  of  the  cerebro-spinal 
centre  and  ganglions,  constituting  a principal  part  of  the  last-mentioned 
ffiodies,  and  thence  often  named  ganglionic  corpuscles  or  ganglion- 
globules ; they  exist  also  in  some  of  the  nerves  of  special  sense.  The 
most  characteristic  form  in  which  the  nerve-cells  present  themselves  is 
that  of  a vesicle,  constructed  of  a fine,  simple,  transparent  cell-mem- 
brane, filled  with  granular  matter,  and  containing  a vesicular  nucleus, 
with  one  or  more  nucleoli.  They  differ  greatly  from  one  another  in 


size ; some  being  scarcely 
larger  than  a human 
blood-corpuscle,  others 
of  an  inch  or  up- 
wards in  diameter.  The 
greater  number  are  sphe- 
roidal in  figure,  especially 
those  found  in  the  ganglia 
(fig.  3 i 5,  A,  a,  b),  but  they 
are  often  more  or  less 
angular,  oblong,  or  irre- 
gular (c,  d),  especially 
when  they  have  been 
closely  packed;  and  they 
are  liable,  too,  to  become 
altered  and  distorted  in 
shape,  in  the  process  of 
extracting  and  insulat- 
ing them.  But  many  of 
the  nerve-cells,  especially 
those  from  the  gray  mat- 
ter of  the  spinal  cord. 


Fig.  315. 


A.  Ganglionic  nerve-cells  detached. 

B and  c.  Small  portions  of  ganglion,  in  which  the  nerve- 


and  certain  rtarts  of  the  cells  are  seen  imbedded  among  the  gelatinous  fibres.  Inc 
pncpritinlAn  rvr-ooont  a ‘hey  are  still  covered  by  their  capsule  of  nucleus-like  cor- 

encepildion,  present  a puscles,  (a,  a.)  Tuhularfibres(6,  6.)  are  seen  passing  through 

very  remarkable  modifi-  the  ganglion;  n indicates  the  nucleus  of  the  nerve-cells  in 
cation  of  figure,  being  figcres.-(From  Valentin,) 

drawn  out  at  one  or  more  points  of  their  circumference  into  long 
filamentous  processes  (fig.  316);  and  these  nerve-cells,  like  other 
nucleated  cells  which  present  this  peculiarity,  are  usually  named 
“ caudate.”  Many  of  them  are  of  a pyriform  shape,  with  their  small 
end  produced  into  a slender  process,  either  simple  or  branched  at  its 


154 


NKRVOUS  SYSTEM. 


extremity  (fig.  31G,  a,  c) ; others  send  out  several  such  processes  from 
diflerent  points.  These  processes  are  formed  of  e.Ktensions  of  the 
cell-membrane,  with  its  inclosed  granular  matter,  and  have  a corre- 
sponding delicacy  of  structure,  so  that  they  frequently  break  off  at 
a short  distance  from  the  vesicle ; they  are  described  by  several 

observers  as  beins  pro- 
[rig.  aio.  longed  into  the  nerve-fibres, 

as  will  hereafter  be  more 
particularly  referred  to. 
Sometimes,  especially  in 
young  animals,  a short  pro- 
cess extends  in  form  of  a 
commissure  from  one  cell 
to  another.  The  nucleus, 
(figs.  315,  n,  and  316,) 
which  takes  no  share  in 
the  caudate  prolongations 
of  the  cell-wall,  is  evidently 
also  of  a vesicular  struc- 
ture; it  has  an  eccentric 
position,  and  a very  regular 
round  or  oval  outline,  usu- 
ally much  more  strongly 
marked  than  that  of  the 
nerve-cell  itself;  its  size, 
too,  is  less  variable.  Some- 
times, though  rarely,  a cell 

Ganglion  globules,  with  their  processes,  nuclei,  and  tWO  nuclei.  The 

nucleoli: — a.  a.  From  the  deeper  part  of  the  gray  matter  nucleolUS  appears  fike  a 
of  the  convolutions  of  the  cerebellum.  The  larger  pro-  UrlrrUt  oni3r>lr  -(s;itliin  th<» 
cesses  are  directed  tow.ards  the  surface  of  the  organ,  b.  o 

Another  from  the  cerebellum,  c.  d.  Others  from  the  post.  llUCleUS  ; it  varies  a gOod 
horn  of  gray  matter  of  the  dorsal  region  of  the  cord,  j ^ 

These  contain  pigment,  which  surrounds  the  nucleus  in.  ’ o 

c.  In  all  these  specimens  the  processes  are  more  or  less  CaseS  aS  large  aS  a human 
broken.— Magnified  200  diameters. — Todd  and  Bowman,]  blogd-parlicle,  and  Some- 
times considerably  larger;  it  would  also  seem  to  be  a vesicular  body. 
There  may  be  two  or  three  nucleoli  in  one  nucleus.  The  matter 
which  fills  the  nerve-cell  is  usually  finely  granular,  and  slightly  tinged 
throughout  with  a brownish-red  colour;  and  cells  are  often  seen,  es- 
pecially those  of  the  large  caudate  kind,  with  one,  or  sometimes  two, 
much  deeper  coloured  brown  patches,  caused  by  groups  of  pigment- 
granules  (fig.  316,  c,  d):  the  colour  is  deeper  in  adult  age  than  in 
infancy. 

Other  nerve-cells  (fig.  317,  a)  are  found  in  the  nervous  substance, 
which  are  distinguished  chiefly  by  the  pellucid,  colourless,  and  homo- 
geneous aspect  of  the  matter  contained  in  them  ; such  cells  possess  a 
nucleus  like  the  rest;  they  are  seldom  large,  and  have  usually  a simple 
round  or  oval  figure.  They  occur  along  with  nerve-cells  of  the  kind 
before  described,  and  are  perhaps  merely  an  earlier  condition  of  these. 
Lastly,  small  vesicular  bodies,  of  the  size  of  human  blood-corpuscles 


CEREBRO-SPINAL  CENTRE. 


155 


Fig.  317. 


a,  cells  from  the  (cortical)  gray  matter 


and  upwards,  containing  one  or  more 
bright  specks  like  nucleoli,  abound  in 
the  gray  matter  in  certain  situations 
(fig.  317,  b,  c).  These  bodies  are 
exactly  like  the  nuclei  of  the  nerve-cells 
already  described,  and  some  of  them 
may  perhaps  be  really  such  nuclei  es- 
caped from  cells  crushed  and  broken 
down  in  the  manipulation  ; but,  looking 
to  their  numbers  and  dense  array  in 
certain  regions  (fig.  317,  c),  their  pre-  _ 

sence  cannot  well  be  generally  referred  of  the  brain,  b and  c are  from  the  corti- 
to  this  cause,  and  it  comes  then  to  be  a Si 

question  whether  they  are  free  nuclei  smaller  bodies,  also  like  cell-nuclei, 
destined  to  become  enclosed  in  a cell  of 
subsequent  formation,  or  actually  cells 

in  which  the  cell-w^all  lies  close  to  the  nucleus,  and  cannot  be  distin- 
guished from  it.  These  nucleus-like  corpuscles  are  very  abundant  in 
the  superficial  gray  matter  of  the  cerebellum. 

In  the  gray  matter  of  the  cerebro-spinal  centre,  the  nerve-cells  are 
usually  imbedded  in  a sort  of  matrix  of  granular  substance,  which  is 
interposed  between  them  in  greater  or  less  quantity,  and  is  very  gene- 
rally traversed  by  nerve-fibres.  In  the  ganglia,  properly  so  called,  the 
cells  are  packed  up  among  nerve-fibres,  chiefly  of  the  gelatinous  kind; 
but  each  cell  is  also  immediately  surrounded  by  a coating  or  capsule 
formed  of  gelatinous  fibres,  and  a layer  of  granular  corpuscles,  not 
unlike  the  most  common  kind  of  granular  cell-nuclei,  united  together 
by  a pellucid  substance  (fig.  315,  c,  a,  a). 

Such  being  the  structural  elements  of  the  nervous  substance,  we 
have  next  to  consider  the  arrangement  of  these  cells  and  fibres  in  the 
organs  which  by  their  combination  they  form  ; namely,  the  spina! 
cord,  the  encephalon,  the  ganglia,  and  the  nerves. 


CEREBRO-SPINAL  CENTRE. 


In  the  spinal  cord,  the  gray  matter  is  situated  in  the  middle;  the 
white  substance,  which  is  in  larger  quantity,  surrounding  and  inclosing 
the  gray.  In  the  encephalon,  the  white  part  also  predominates  in  mass, 
and  incloses  large  internal  deposits  of  gray  substance  ; but  a very  large 
amount  of  the  latter  is  spread  over  the  white,  on  the  convoluted  sur- 
face of  the  brain  and  cerebellum,  and  is  thence  named  the  cortical 
substance.  Both  kinds  of  matter  receive  blood-vessels,  but  the  gray 
is  greatly  more  vascular  than  the  white. 

Gray  -part  of  the  spinal  cord. — The  gray  part  of  the  cord,  as  else- 
where described,  represents  in  a transverse  section  two  lateral 
crescents,  with  their  cornua  averted  and  their  convexities  connected 
across  the  median  plane  by  a gray  commissure.  The  posterior  horns 
of  this  bicrescentic  figure  consist,  towards  their  points,  of  a peculiar 
variety  of  gray  matter,  named  gelatinous  by  Rolando,  who  appears 


J56 


NERVOUS  SYSTEM. 


first  to  have  distinguished  it : the  remaining  and  greater  part  of  the 
gray  substance  is  of  the  kind  most  generally  prevalent,  and  was  named 
by  Rolando  the  spongy  substance.  Remak*  describes  the  gelatinous 
substance  as  passing  along  the  posterior  part  of  the  posterior  cornua, 
and  then  across  from  one  side  of  the  cord  to  the  other,  so  as  to  form 
the  back  part  of  the  gray  commissure. 

Examined  with  the  microscope,  the  gray  matter  of  the  cord  is  found 
to  consist  of  the  following  elements,  viz. 

1.  Large  caudate  nerve-cells,  such  as  those  represented  in  fig.  316. 
These  are,  in  a great  measure,  confined  to  the  spongy  substance,  but, 
according  to  Hannover,f  are  also  met  with,  though  sparingly,  in  the 
gelatinous  part.  They  lie  imbedded  among  fibres,  to  be  presently  no- 
ticed, with  a certain  amount  of  the  usual  granular  matrix.  Most  of  them 
belong  to  the  class  of  largest-sized  nerve-cells  ; they  contain  large  nu- 
clei, and  often  collections  of  dark-coloured  pigment,  and  most  are 
furnished  with  several  very  long  simple  or  branched  processes,  which 
traverse  the  intervening  space  in  various  directions. 

2.  Pale  fibres.  The  gelatinous  substance  is  described  by  Remak 
as  being  principally  made  up  of  fibres  of  this  kind,  which  run  longitu- 
dinally, and  in  very  dense  order;  he  finds  similar  fibres  also  in  the 
spongy  substance,  where,  however,  they  are  much  obscured  by  other 
structures.  From  their  resemblance  to  the  filamentous  processes 
of  the  caudate  nerve-cells,  it  has  been  conjectured  that  they  may  be 
an  reality  prolonged  from  these  appendages;  but  this  view  is  not  free 
from  objection.  These  pale  fibres  are  beset  with  numerous  corpuscles 
resembling  common  cell-nuclei,  and  Remak  states  that  in  young  animals 
these  apparent  nuclei,  or  other  nuclear  corpuscles  like  them,  are  in- 
closed in  pellucid  colourless  cells.J  It  must  be  remembered  that  the 
capillary  vessels,  which  are  very  numerous  in  the  gray  matter,  are 
covered  with  corpuscles  of  the  same  description  as  those  above  men- 
tioned. 

3.  Tubular  fibres.  Such  fibres  exist  abundantly  both  in  the  spongy 
and  gelatinous  substance,  but  more  so  in  the  former.  Their  arrange- 
ment, and  their  relations  to  the  other  structures  in  the  gray  matter, 
are  not  fully  known  ; they  are  continued  from  the  white  substance, 
and,  in  part  at  least,  belong  to  the  roots  of  the  spinal  nerves,  with 
which  they  will  presently  be  further  considered. 

White  part  of  the  cord. — The  white  substance  of  the  cord  consists  of 
tubular  fibres,  of  smaller  average  size  than  those  of  the  nerves,  and 
apparently  of  more  delicate  structure,  for  they  readily  become  varicose. 
They  are  collected  into  bundles  and  lamince,  between  which  lie  vessels 
and  a few  fibres  of  cellular  tissue,  and  hence  the  fibrous  and  lamellar 
character  visible  in  the  white  substance  to  the  naked  eye.  The  gene- 
ral direction  of  the  fibres  is  longitudinal,  but  some  are  described  as 
passing  obliquely  or  directly  across  in  the  commissures  from  one  half 
of  the  cord  to  the  other ; the  exact  extent  and  connexions  of  these 

* De  Systcmatis  Nervosi  Structura,  Berol.  1838,  p.  12. 

t Recherches  microscopiques  sur  le  Syst^me  Nerveux.  Copenhague  et  Paris,  1844. 

} Muller’s  Archiv.  1841,  p.  514. 


CEREBRO  SPINAL  CENTRE. 


157 


crossing  fibres  have  not  been  made  out.  Of  the  longitudinal  fibres, 
some  are  continued  into  the  roots  of  the  spinal  nerves;  but  this  does 
not  appear  to  be  the  case  with  all ; for  it  seems  probable  that  there  are 
fibres  which,  without  passing  into  the  nerves,  extend  longitudinally 
from  one  part  of  the  cord  to  another,  uniting  the  gray  matter  of  its 
different  regions,  and  connecting  also  the  upper  part  of  the  cord  with 
the  cerebellum,  medulla  oblongata,  and  cerebrum. 

The  root  of  each  spinal  nerve,  as  will  be  more  fully  described  here- 
after, is  attached  to  the  white  part  of  the  cord  by  one  portion  of  its  fibres, 
whilst  the  remainder  pass  horizontally,  or  with  a slight  upward  obli- 
quity, into  the  gray  matter.  The  former  set  of  fibres  can  be  shown 
to  be  continuous  with  longitudinal  fibres  of  the  cord,  which  are  said 
to  descend  at  first  vertically,  and  then  to  take  a slanting  direction  to- 
wards the  surface,  where  they  are  continued  into  the  root  of  the  nerve. 
Whether  these  longitudinal  fibres,  thus  continuous  below  with  the 
nerves,  are  all  connected  by  their  upper  extremity  with  the  encephalon, 
as  is  most  commonly  believed,  or  whether  they  take  their  rise,  in  whole 
or  in  part,  in  }he  gray  substance  of  the  upper  region  of  the  cord,  as 
some  think,  must  still  be  considered  doubtful.  The  fibres  of  the  cord, 
in  passing  into  the  nerve,  put  off  their  varicose  character,  and  increase 
in  size,  as  shown  in  fig.  313.  Those  fibres  of  the  nerve-roots  which 
are  traced  into  the  gray  matter,  are  supposed  by  some  anatomists  (e. 
g.  Valentin)  merely  to  pass  through  that  substance,  and  then  to  ascend 
in  the  white  part  of  the  cord ; but  from  a consideration  of  the  compa- 
rative thickness  of  the  cord  at  different  heights,  and  of  the  structure 
of  what  are  deemed  analogous  parts  of  the  nervous  system  in  inverte- 
brate animals,  as  well  as  for  reasons  derived  from  physiological  phe- 
nomena, it  is  more  generally  thought  that  the  nervous  fibres  in  question 
take  their  origin  in  the  gray  matter. 

As  to  the  manner  in  which  this  takes  place,  as  indeed  respecting  the  mode  of 
origin  of  nerve-fibres  generally,  there  are  two  very  different  views.  Some  sup- 
pose that  when  nerve-fibres  arise  or  terminate  in  gray  matter,  they  form  loops  or 
slings,  which'lie  among  the  nerve-cells  and  other  elements  of  that  substance, 
each  loop  of  course  corresponding  to  two  fibres  in  the  nerve ; according  to  others, 
the  fibres  arise  from  the  caudate  nerve-cells,  being  merely  prolongations  of  the 
filamentous  processes  issuing  from  these  bodies,  which,  after  proceeding  a little 
distance  from  the  cell,  acquire  the  character  of  tubular  fibres.  Admitting  the 
probable  origin  of  nerve-fibres  in  the  gray  substance,  still,  from  the  uncertainty, 
or,  at  any  rate,  the  acknowledged  difficulty  of  all  observations  on  the  subject,  the 
precise  mode  in  which  they  are  related  to  its  elements  can  scarcely  be  considered 
as  fully  determined ; although  the  testimony  of  many  competent  observers,  who 
declare  that  they  have  been  able  unequivocally  to  trace  the  continuity  of  lierve- 
fibres  with  the  nerve-cells,*  leaves  no  longer  room  to  doubt  that  that  is  at  least 
one  mode  in  which  they  arise. 

White  part  of  the  encephalon. — The  white  matter  of  the  encephalon 
consists  of  tubular  fibres,  in  general  still  smaller  than  those  of  the  cord, 
and  still  more  prone  to  become  varicose.  The  general  direction 

* Helmholz  and  Will  in  invertebrate  animals ; Kolliker  in  the  frog ; and  Hannover  in  all 
classes  ofvertebrata,  as  well  as  in  several  invertebrata.  In  the  electric  lobes  of  the  brain  of 
the  torpedo,  by  Harless,  wlio  states  that  he  found  the  nerve-fibre  to  be  connected  with  the 
nucleus  of  the  cell.  Also  Robin  and  Wagner  in  the  ganglia  of  various  cartilaginous  fishes. 

VOL.  II.  14 


15S 


NERVOUS  SYSTEM. 


which  they  follow  is  best  seen  in  a brain  that  has  been  hardened  by 
immersion  in  spirits,  although  it  is  true  that  we  do  not  then  trace  the 
single  fibres,  but  only  the  fine  bundles  and  fibrous  lamellae  which  they 
form  by  their  aggregation ; and  a detailed  account  will  be  given  else- 
where of  their  course  and  apparent  connexions,  as  far  as  has  been 
made  out  in  this  manner. 

It  may  suffice  here  to  remark,  that  one  large  body  of  fibres  can  be  traced  up- 
wards from  the  spinal  cord  to  the  gray  matter  situated  in  different  regions  of  the 
encephalon ; some  of  these  fibres  reaching  as  high  as  the  cortical  layer  on  the 
surface  of  the  cerebrum  and  cerebellum,  others  apparently  terminating  in  the 
corpus  striatum,  thalamus  opticus,  corpora  quadrigemina,  and  other  special  de- 
posits of  gray  substance.  These  fibres  are  generally  believed  to  be  continued  by 
their  lower  ends  into  the  spinal  nerves,  though  it  is  also  supposed  that  part  of 
them  may  terminate  below  in  the  gray  matter  of  the  cord.  Other  fibres  pass  be- 
tween different  parts  of  the  encephalon  itself,  serving  most  probably  to  connect 
its  different  masses  of  gray  substance  : among  the  more  conspicuous  examples  of 
these  may  be  adduced  the  fibres  connecting  the  cerebrum  and  cerebellum,  form- 
ing what  are  called  the  superior  cerebellar  peduncles ; fibres  passing  up  from  the 
gray  matter  in  the  medulla  oblongata  and  annular  protuberance,  in  company 
with  those  from  the  spinal  cord,  and  having  probably  a similar  connexion  supe- 
riorly ; fibres  radiating  from  the  corpus  striatum  to  the  cortical  gray  matter  of  the 
cerebrum;  fibres  extending  between  adjacent  or  distant  convolutions;  and,  lastly, 
the  vast  body  of  fibres  belonging  to  the  commissures  of  the  cerebram  and  middle 
crura  of  the  cerebellum  which  pass  from  one  side  of  the  encephalon  to  the  other_ 

Gray  part  of  the  encephalon. — The  cortical  gray  matter  which 
covers  the  foliated  surface  of  the  cerebellum  is  made  up  of  the  follow- 
ing elements,  viz.:  1.  Pellucid  cells  of  considerable  size,  [fig.  318,  b, a.] 
2,  Cells,  for  the  most  part  caudate,  having  the  usual  granular  contents. 
The  cells  are  imbedded  in  a finely  granular  matrix;  the  greater 
number  of  those  of  the  caudate  kind  have  a pyriform  shape,  and  are 
prolonged  at  their  small  end  into  a simple  or  branched  appendage,  as 
represented  in  fig.  316,  a,  c,  and  this  process,  as  first  remarked  by 
Purkinje,  is  in  most  of  them  directed  towards  the  surface  of  the  cere- 
bellum. 3.  Small  bodies  like  cell-nuclei  (fig.  317,  c),  densely  aggre- 
gated without  any  intervening  substance.  These  lie  at  some  depth 
from  the  surface;  according  to  Dr.  Todd,  they  form  a thin  light- 
coloured  lamina,  intermediate  between  two  darker  strata  of  gray 
matter,  which  contain  the  nerve-cells  ; one  of  these  gray  strata  being 
next  the  white  matter  of  the  cerebellum,  while  the  other,  which  is  the 
deeper  coloured  of  the  two,  is  in  contact  with  the  pia  mater.  4. 
Fibres.  Tubular  nerve-fibres  pass  from  the  white  into  the  gray 
matter,  and  extend  through  it  nearly  as  far  as  the  surface.  According 
to  Valentin,  they  form  loops  and  return,  but  this  statement  has  not 
been  confirmed  by  other  observers. 

The  gray  matter  on  the  convoluted  surface  of  the  cerebrum  is 
divided  into  two,  and  in  some  regions  into  three,  strata,  by  interposed 
thin  layers  of  white  substance.  In  examining  it  from  without  inwards, 
we  meet  with,  1,  a thin  coating  of  white  matter  situated  on  the  surface, 
which  on  a section  appears  as  a faint  white  line,  bounding  the  gray 
substance  externally  (fig.  319,  a,  a).  This  superficial  white  layer  is 
not  equally  thick  over  all  parts  of  the  cortical  substance,  but  becomes 
thicker  as  it  approaches  the  borders  of  the  convoluted  surface;  it  is 
accordingly  less  conspicuous  on  the  lateral  convex  aspect  of  the 


GRAY  PART  OF  ENCEPHALON. 


159 


hemispheres,  and  more  so  on  the  convolutions  situated  in  the  longi- 
tudinal fissure  which  approach  the  white  surface  of  the  corpus  callo- 
sum, and  on  those  of  the  under  surface  of  the  brain.  It  is  especially 

[Fig.  318.  Fig.  319. 


[Fig.  318.  A.  Blendingof  the  vesicular  and  fibrous 
nervous  matter  in  the  dentate  body  of  the  cere- 
bellum:— a.  Ganglion  globule,  with  its  nucleus  and 
nucleolus,  h.  Nerve-tube,  slightly  varicose,  in  close 
contact  with  the  ganglion  globule,  b'.  Smaller 
nerve-tubes.  These  parts  all  lie  in  a finely  granular  matrix  interspersed  with  nuclei,  c.  b.  Ve- 
sicular and  fibrous  matter  of  the  laminae  of  the  cerebellum,  a.  Ganglion  globule,  b.  Very  mi- 
nute nerve-tubes  traversing  a finely  granular  matrix,  in  which  are  numerous  rounded  nuclei,  c. — 
-Todd  and  Bowman.] 

Fig.  319.  A.  Section  of  the  gray  substance  of  the  convolutions  of  the  cerebrum.  At  the  upper 
part  of  the  figure  a and  e are  two  white,  and  b and/ two  gray  strata.  At  the  lower  part  of  the 
figure  an  additional  white  layer  (c)  divides  the  first  gray  layer  into  two,  b and  d.  (From  Remak.) 

B.  Plan  to  show  the  general  arrangement  of  the  fibres  and  cells  in  the  conical  substance.  The 
letters  a,  b,  c,  d,  e,f,  indicate  the  same  strata  as  in  figure  a ; g shows  fibres  coming  from  the  cen- 
tral white  matter  of  the  brain,  and  intersecting  the  stratified  white  fibres  of  the  cortical  substance. 
(Remak.) 

well  marked  on  the  middle  lobe,  near  the  descending  cornu  of  the 
lateral  ventricle,  where  the  convoluted  surface  is  bounded  by  the 
posterior  pillar  of  the  fornix,  and  it  has  been  there  described  under  the 
name  of  the  reticulated  white  substance.  It  consists  of  remarkably 
fine  tubular  fibres,  for  the  most  part  varicose,  which  run  parallel  with 
the  surface  of  the  convolutions,  but  intersect  each  other  in  various 
directions.  The  termination  and  connexions  of  these  fibres  are  un- 
known. 2dly.  Immediately  beneath  the  white  layer  just  described, 
comes  a comparatively  thick  layer  of  gray,  or  reddish  gray,  matter 
(fig.  319,  A,  h),  the  colour  of  which,  as  indeed  of  the  gray  substance 
generally,  is  deeper  or  lighter  according  as  its  very  numerous  vessels 
contain  much  or  little  blood.  Then  follow,  2dly,  another  thin  whitish 
layer  (e),  and,  Athly,  a thin  gray  stratum  (/) ; this  last  lies  next  to  the 
central  white  matter  of  the  hemisphere:  Remak  considers  it  as  similar 
in  nature  to  the  gelatinous  substance  of  the  spinal  cord.  According 
to  this  account,  the  cortical  substance  consists  of  two  layers  of  gray 
substance,  and  two  of  white;  but  in  several  convolutions,  especially 
those  situated  near  the  corpus  callosum,  a third  white  stratum  may  be 


160 


NERVOUS  SYSTEM. 


seen  (inHicated  by  c at  the  lower  end  of  the  figure),  which  divides  the 
most  superficial  gray  one  into  two  {b  and  d),  thus  making  six  in  all, 
namely,  three  gra}^  and  three  white. 

The  cortical  gray  substance  consists  of  nerve-cells  of  rather  small 
size,  usually  round  or  oval  and  seldom  caudate,  lying  in  a granular 
matrix ; also  of  small  nucleus-like  vesicles,  like  those  seen  in  the 
cortical  substance  of  the  cerebellum  (fig.  317,  c),  and,  according  to 
Dr.  Todd,  here  also  collected  into  a special  stratum.  Tubular  fibres 
exist  throughout ; one  set  of  them  run  parallel  with  the  surface,  and  at 
certain  depths  are  more  densely  aggregated,  so  as  to  form  the  before- 
mentioned  w'hite  layers  (fig.  319,  b,  a,  c,  e) ; but  they  are  not  wanting 
in  the  intervening  gray  strata  {b,  d,  f),  only  they  are  there  wider 
apart.  The  manner  in  which  they  begin  and  end  is  not  known;  it 
seems  not  improbable,  however,  that  they  are  dependencies  of  the 
commissural  system  of  fibres.  These  stratified  fibres,  if  they  might  be 
so  called,  are  intersected  by  another  set  of  tubular  fibres  (g),  which 
come  from  the  central  white  mass  of  the  hemispheres,  and  run  per- 
pendicularly through  the  cortical  substance,  becoming  finer  and 
spreading  more  out  from  each  other  as  they  approach  the  surface. 

The  further  disposition  of  these  central  or  perpendicular  fibres  is  Uncertain ; 
Valentin  describes  them  as  forming  terrninal  loops  or  arches,  but  this  is  denied 
by  Remak  and  Hannover.  Remak  states  that  they  gradually  disappear  from  view 
at  different  depths,  as  they  pass  through  the  successive  layers,  the  last  of  them 
vanishing  in  the  superficial  gray  stratum ; but  he  is  unable  to  say  positively  how 
they  terminate  : it  sometimes  seemed  to  him  as  if  the  last  of  them,  after  inter- 
secting the  fibres  of  the  deeper  white  strata,  became  continuous  with  those  of  the 
outermost  layer;  but  of  this  he  by  no  means  speaks  confidently.  Hannover 
maintains  that  they  are  connected  at  their  extremities  with  the  nerve-cells  in  the 
cortical  substance. 

As  regards  the  other  collections  of  gray  matter  in  the  encephalon, 
it  may  be  remarked  that  they  consist  of  nerve-cells  and  intercellular 
granular  matter,  with  tubular  fibres  in  greater  or  less  number;  the 
following  details  respecting  them  are  given  chiefly, on  the  authority  of 
Hannover: — 

The  corpus  striatum  and  optic  thalamus  contain  cells  very  much  like  those  of 
the  cortical  substance.  In  the  corpora  quadrigemina  there  are  larger  cells,  ap- 
oroaching  in  size  to  those  of  the  cerebellum,  besides  very  small  cells  and  nuclei- 
lorm  bodies.  The  dark  matter,  forming  the  so-called  locus  niger  of  the  cerebral 
peduncles,  and  that  in  the  floor  of  the  fourth  ventricle,  contain  caudate  cells, 
many  of  them  of  the  largest  .size,  with  long  appendages,  and  deeply  coloured 
with  pigment.  In  the  pineal  gland  the  cells  are  larger  than  those  of  the  cerebral 
convolutions,  but  with  comparatively  small  nuclei,  and  many  of  them  contain 
particles  of  earthy  matter;  there  are  but  few  of  the  nucleus-like  corpuscles. 
The  anterior  lobe  of  the  pituitary  body  contains  dark  nerve-cells  of  moderate 
size,  with  coarsely  granular  contents,  along  with  isolated  nucleiform  bodies. 
The  posterior  lobe,  on  the  other  hand,  consists  of  very  large  cells  of  soft  con- 
sistence and  variable  irregular  shape,  containing  comparatively  small  nuclei 
without  nucleoli.  Many  of  these  last-mentioned  cells  are  furnished  with  ap- 
pendages, and  it  is  not  uncommon  to  meet  with  two  united  together  by  a sort  of 
commissure.* 

* Rathke  considers  the  pituitary  body  as  belonging  to  the  same  class  of  organs  as  the 
thyroid  ffland,  suprarenal  bodies,  the  spleen,  &c.  As  far  as  I can  judge  from  the  exami- 
nations I have  been  able  to  make  of  it,  it  differs  greatly  in  structure,  at  least  in  its  anterior 
and  larger  lobe,  from  any  other  part  of  the  encephalon.  The  substance  of  the  anterior  lobe 
has  appeared  to  me  to  be  constituted  by  a membranous  tissue  forming  little  round  cavities 
or  loculi,  which  are  packed  full  of  nucleated  cells.  The  loculi  are  formed  of  transparent, 


GANGLIA. 


161 


OF  THE  ganglia. 

The  bodies  so  named  are  found  in  the  following  situations,  viz. : 
1.  On  the  posterior  root  of  each  of  the  spinal  nerves,  on  one,  and  pro- 
bably the  corresponding  root  of  the  fifth  nerve  of  the  encephalon,  and 
on  the  seventh  pair,  glossopharyngeal  and  pneumogastric  nerves, 
involving  a greater  or  less  amount  of  their  fibres.  2.  Belonging  to 
the  sympathetic  nerve.  («)  In  a series  along  each  side  of  the  verte- 
bral column,  connected  by  nervous  cords,  and  constituting  what  was 
once  considered  as  the  trunk  of  the  sympathetic,  (b)  On  branches  of 
the  sympathetic;  occurring  numerously  in  the  abdomen,  thorax,  neck, 
and  head ; generally  in  the  midst  of  plexuses,  or  at  the  point  of  union 
of  two  or  more  branches.  Those  which  are  found  in  several  of  the 
fossae  of  the  cranium  and  face  are  for  the  most  part  placed  at  the 
junction  of  fine  branches  of  the  sympathetic  with  branches,  usually 
larger,  of  the  cerebro-spinal  nerves;  but  they  are  generally  reckoned 
as  belonging  to  the  sympathetic  system. 

The' ganglia  differ  widely  from  each  other  in  figure  and  size  : those 
which  have  been  longest  known  to  anatomists  are  most  of  them  large 
and  conspicuous  objects;  but,  from  the  researches  of  Remak,  it  ap- 
pears that  there  are  numerous  small,  or  what  might  be  almost  termed 
microscopic  ganglia,  connected  with  the  nerves  of  the  heart,  lungs, 
and  some  other  viscera. 

Ganglions  are  invested  externally  with  a thin  but  firm  and  closely 
adherent  envelope,  continuous  with  the  neurilemma  or  sheath  of  the 
nerves,  and  composed  of  dense 

cellular  tissue:  this  outward  co-  [Fig. 320. 

vering  sends  processes  inwards 
through  the  interior  mass,  dividing 
it,  as  it  were,  into  lobules,  and 
supporting  the  numerous  fine  ves- 
sels which  pervade  it.  A section 
carried  through  a ganglion,  in  the 
direction  of  the  nervous  cords  con- 
nected with  it,  discloses  to  the 
naked  eye  merely  a collection  of 
reddish-gray  matter  traversed  by 
the  white  fibres  of  the  nerves. 

The  nervous  cords  on  entering 
the  ganglion  lay  aside  their  mem- 
branous sheath,  and  spread  out  - „ ^ ■ v c j , 

. ’ 11  ^ 1 rrom  the  Gasserian  ganglion  of  an  adult: — 

into  smaller  bundles,  between  a.  a.  Ganglion  globules  with  their  nucleus, 
which  the  gray  ganglionic  sub-  capsule,  and  pigment,  t.  Tubular 

, . . 1 rnt  • fibres,  running  among  the  globules  in  contact 

Stance  is  interposed.  1 he  micro-  with  their  capsule,  g.  Gelatinous  fibres  also  in 

scope  shows  that  this  gray  sub-  Sl°^“*®®  "~^^snified 

stance  consists  of  nerve-cells  and 


320  diameters. — Todd  and  Bowman.] 


simple  membrane,  with  a few  fibres  and  corpuscles  resembling  elongated  cell-nuclei  dis-* 
posed  round  their  walls.  The  cells  contained  in  the  cavities  were  of  various  sizes  and 
shapes,  and  not  unlike  nerve  cells  or  ganglion  globules;  they  were  collected  into  round 
clusters,  filling  the  cavities,  and  were  mixed  with  a semifluid  granular  substance.  I’his 
thin  granular  matter,  together  with  the  cells  and  little  specks  of  a clear  glairy  substance 
like  mucus,  could  be  squeezed  from  the  cut  surface  in  form  of  a thick,  white,  creamlike 
fluid. 


14* 


1G2 


NERVOUS  SYSTEM. 


gelatinous  fibres.  The  nerve-cells,  or  ganglion  globules,  [fig.  320,  a,] 
have  mostly  a round  or  oval  figure,  especially  those  situated  towards  the 
surface  of  the  ganglion  ; those  nearer  the  centre  are  often  angular  or 
pointed,  and  some  have  caudate  processes  ; these  last  are  rare,  or,  at 
least,  dillicult  to  see,  in  the  ganglia  of  warm-blooded  animals,  but  they 
abound  in  those  of  cartilaginous  fishes.  Their  cell-wall  is  said  to  be 
stronger  than  that  of  the  cells  found  in  the  brain  and  spinal  cord,  and 
they  are  moreover  inclosed  in  capsules  formed  of  granular  corpuscles 
and  gelatinous  fibres,  out  of  which  they  readily  escape  when  the  gan- 
glion is  torn  up  into  fragments.  The  tubular  nerve  fibres,  [fig.  320, 
<,]  are,  according  to  Valentin,  disposed  as  follows:  one  part  of  them, 
(fibrse  transeuntes,)  keeping  together  in  considerable  bundles,  run 
straight  through  the  ganglion  ; the  rest  (fibrae  circuniflexm  seu  circum- 
nectentes)  separate  more  from  each  other,  and  take  a circuitous 
course  among  the  nerve-cells,  round  which  they  make  various  turn- 
ings and  windings  before  passing  out  of  the  ganglion.  The  bundles 
of  straight  fibres  usually  keep  near  the  middle  of  the  ganglion  and  are 
then  surrounded  by  the  globules,  but  frequently  they  run  on  one  side. 
The  winding  fibres  generally  run  nearer  the  surface;  and  when  a 
series  of  ganglia  are  connected  by  a nervous  cord,  as  in  the  trunk  or 
main  part  of  the  sympathetic,  it  would  seem  that  these  winding  fibres 
are  destined  to  pass  out  in  the  branches  given  off  from  the  ganglionic 
chain,  whilst  the  straight  fibres  run  on  unchanged  through  two  or 
three  successive  ganglia,  until  at  length  they  in  their  turn  assume  the 
winding  arrangement,  approach  the  surface,  and  pass  oflT  into  branches. 
The  gelatinous  fibres,  [fig.  320, g-,]  leaving  the  ganglion,  pass  along  the 
nervous  cords  with  the  tubular  fibres,  and  their  arrangement  will  be 
afterwards  further  noticed. 

Remak  and  Hannover  state  that  gelatinous  fibres  arise  from  the 
ganglion  globules:  Valentin,  who  denies  the  nervous  nature  of  these 
fibres,  maintains  that  they  are  connected  only  with  the  inclosing  cap- 
sules of  the  ganglion  globules,  and  not  immediately  with  the  globules 
themselves.  As  regards  the  connexion  of  the  tubular  fibres  with  the 
ganglia,  there  is  also  a difference  of  opinion  among  those  observers 
who  have  made  this  difficult  point  in  anatomy  a subject  of  special  in- 
quiry. According  to  Valentin,  these  tubular  fibres  are  all  derived 
from  the  brain  or  spinal  cord,  and  pass  through  the  ganglia,  coming, 
it  is  true,  into  close  proximity  and  intimate  functional  relation  with 
the  ganglion  globules,  but  none  either  originating  or  terminating  in  a 
ganglion.  It  is  contended  by  others  that  a part  of  the  fibres  in  ques- 
tion take  their  rise  in  the  ganglia,  and  this  opinion  is  maintained 
principally  on  the  two  following  grounds: — 1.  The  observation  of 
Bidder  and  Volkman,  in  which  Kolliker  concurs,  that  in  many  cases 
the  communicating  nervous  cords  which  conduct  tubular  fibres  from 
the  cerebro-spinal  centre  to  the  ganglia  contain  manifestly  fewer  of 
these  fibres  than  are  contained  in  the  branches  which  pass  off  from 
the  ganglia  to  be  distributed  peripherally.  2.  The  statement  of  several 
observers,  among  others  of  Hannover  and  Kolliker,  that  they  have 
been  able  actually  to  trace  the  continuity  of  the  fibres  in  question  with 
the  caudate  processes  of  the  ganglion  globules.  These  observations 


CEREBRO-SPINAL  NERVES. 


163 


would  doubtless  settle  the  question,  were  their  correctness  established  ; 
but  it  must  be  admitted  that  they  are  not  free  from  fallacy,  and  still 
stand  in  need  of  confirmation.* 

CEKEBRO-SPINAL  NERVES. 

These  are  formed  of  the  nerve-fibres  already  described,  collected 
together  and  bound  up  in  membranous  sheaths.  A larger  or  smaller 
number  of  fibres  enclosed  in  a tubular  sheath  form  a little  round  cord, 
usually  named  a funiculus;  if  a nerve  be  very  small,  it  may  consist  of 
but  one  such  cord,  but  in  larger  nerves  several  funiculi  are  united 
together  into  one  or  more  larger  bundles,  which,  being  wrapped  up 
in  a common  membranous  covering,  constitute  the  nerve,  (fig.  321.) 
Accordingly,  in  dissecting  a nerve,  we  first  come  to  an  outward 


Fig.  321. 


Represents  a nerve  consisting  of  many  smaller  cords  or  funiculi  wrapped  up  in  a common 
celliiiar  sheath. — a,  the  nerve.  B.  A single  funiculus  drawn  out  from  the  rest.  (After  Sir  C. 
Bell.) 

covering,  formed  of  cellular  tissue,  but  often  so  strong  and  dense  that 
it  might  well  be  called  fibrous.  From  this  common  sheath  we  trace 
laminae  passing  inwards  between  the  larger  and  smaller  bundles  of 
funiculi,  and  finally  between  the  funiculi  themselves,  connecting  them 
together  as  well  as  conducting  and  supporting  the  fine  blood-vessels 
which  are  distributed  to  the  nerve.  But,  besides  the  interposed  cel- 
lular tissue  which  connects  these  smallest  cords,  each  funiculus  has  a 

* Since  the  above  was  written,  the  alleged  connexion  of  tubular  fibres  with  ganglionic 
cells  has  been  confirmed  in  a very  decided  manner  by  Wagner,  who  states  that  he  has 
been  able  to  trace  it  most  unequivocally  in  the  ganglia  of  the  spinal  nerves,  trigeminus  and 
vagus  of  the  torpedo,  skate,  and  dog-fish,  in  which,  from  the  small  amount  of. cellular 
tissue  intermixed,  the  nervous  fibres  can  be  followed  with  comparative  ease.  He  has  also 
succeeded  in  observing  it  in  the  sympathetic  ganglia  of  some  of  those  fishes.  He  finds 
that  almost  invariably  two  fibres  are  connected  with  each  ganglion-cell,  at  opposite  sides 
or  opposite  poles,  as  it  were,  one  directed  centrally  or  towards  the  root  of  the  nerve,  and 
the  other  outwardly  towards  its  branches,  and  he  thence  infers  that  every  fibre  which 
issues  from  a ganglion-cell  corresponds  to  an  entering  one  with  which  it  is  connected 
through  the  medium  of  the  cell,  and  that  there  is  no  multiplication  of  the  fibres  in  a gan- 
glion.  The  nerve  fibre,  as  it  leaves  the  cell,  appears  like  a mere  prolon^tion  from  it, 
containing  the  same  kind  of  granular  matter;  but  further  on  it  enlarges  and  acquires  the 
dark  double  contour,  indicating  the  presence  of  the  white  substance.  The  cell-wall  ap- 
pears  to  be  continuous  with  the  sheath  (tubular  membrane)  of  the  fibre,  which  in  these 
fishes  is  remarkably  strong.  Some  cells,  generally  smaller  than  the  rest,  are  uncon- 
nected with  fibres.  (See  Rudolph  Wagner,  fiber  den  Bau  und  Endigung  der  Nerven. 
Leipz.  1847 ; and  Ann.  des  Sc.  Nat.,  March,  1847.) 

Robin  has  also  observed,  in  the  spinal  ganglia  of  the  skate,  ganglion  globules  each  with 
two  tubular  nerve-fibifes  connected  at  opposite  poles.  He  states  also  that  he  saw  smaller 
ganglion  globules,  similarly  connected  with  smaller  or  sympathetic  nerve-fibres.  (Ann. 
des  Sc.  Nat.,  Avril,  1847  ) 

On  repeating  Wagner’s  observation  on  the  spinal  ganglia  of  the  common  skate  along 
with  my  friend  Professor  A.  Thomson,  of  Edinburgh,  we  very  readily  found  ganglion 
globules  with  a tubular  fibre  proceeding  from  tlieir  opposite  poles,  as  described  by  Wagner. 


164 


NERVOUS  SYSTEM. 


distinct  and  independent  tubular  sheath  of  its  own,  as  will  be  further 
noticed  presently. 

The  common  slieath  and  its  subdivisions  consist  of  cellular  tissue, 
presenting  the  usual  white  and  yellow  constituent  fibres  of  that  tex- 
ture, the  latter  being  present  in  considerable  proportion.  The  tubular 
sheaths  of  the  funiculi,  on  the  other  hand,  appear  to  be  formed  essen- 
tially of  a fine  transparent  membrane,  which  may  without  difficulty  be 
stripped  off  in  form  of  a tube  from  the  little  bundle  of  nerve  fibres  of 
which  the  funiculus  consists.  When  examined  with  a high  power  of 
the  microscope,  this  membrane  presents  the  aspect  of  a thin  transpa- 
rent film,  which  in  some  parts  appears  to  be  quite  simple  and  homo- 
geneous, but  is  more  generally  marked  with  extremely  fine  reticulated 
fibres.  Corpuscles  resembling  elongated  cell  nuclei  may  also  be  seen 
upon  it  when  acetic  acid  is  applied.*  The  tissue  investing  a nerve 
and  inclosing  its  proper  fibres,  as  now  described,  is  named  the  neuri- 
lemma,SiwA  the  term  is  for  the  most  part  applied  indiscriminately  to  the 
whole  of  the  enveloping  structure,  though  some  anatomists  use  it  to 
denote  only  the  sheaths  of  the  funiculi  and  smaller  fasciculi,  vvhilst 
they  name  the  general  external  covering  of  the  nerve  its  “ cellular 
sheath”  {vagina  cellulosa). 

The  funiculi  of  a nerve  are  not  all  of  one  size,  but  all  are  sufficiently 
large  to  be  readily  seen  with  the  naked  eye,  and  easily  dissected  out 
from  each  other.  In  a nerve  so  dissected  into  its  component  funiculi, 
it  is  seen  that  these  do  not  run  along  the  nerve  as  parallel  insulated 
cords,  but  join  together  obliquely  at  short  distances  as  they  proceed  in 
their  course,  the  cords  resulting  from  each  union  dividing  in  their 
further  progress  to  form  junctions  again  with  collateral  cords  ; so  that 
in  fact  the  funiculi  composing  a single  nervous  trunk  have  an  arrange- 
ment with  respect  to  each  other  similar  to  that  which  we  shall  pre- 
sently find  to  hold  in  a plexus  formed  by  the  branches  of  different 
nerves.  It  must  be  distinctly  understood,  however,  that  in  these  com- 
munications the  proper  nerve-fibres  do  not  join  together  or  coalesce. 
They  pass  off  from  one  nervous  cord  to  enter  another,  with  whose 
fibres  they  become  intermixed,  and  part  of  them  thus  intermixed  may 
again  pass  off  to  a third  funiculus,  or  go  through  a series  of  funiculi 
and  undergo  still  further  intermixture ; but  throughout  all  these  suc- 
cessive associations  the  nerve-fibres  remain,  as  far  as  known,  individu- 
ally distinct,  like  interlaced  threads  in  a rope. 

The  fibres  of  the  cerebro-spinal  nerves  are  chiefly,  in  some  cases 
perhaps  exclusively,  of  the  tubular  kind,  but  in  most  instances  there 
are  also  gelatinous  fibres  in  greater  or  less  number.  Moreover,  it  has 
often  appeared  to  me  as  if  there  were  filaments  of  extreme  tenuity, 
like  the  white  filaments  of  cellular  tissue,  mixed  up  with  the  true  nerve- 
fibres  within  the  sheaths  of  the  funiculi.  Lying  alongside  each  other, 
the  fibres  of  a funiculus  form  a little  skein  or  bundle,  which  runs  in  a 
waving  or  serpentine  manner  within  its  tubular  sheath ; and  the  alter- 

* In  several  observations  it  has  seemed  to  me  that  these  corpuscles  were  attached  to  the 
inner  surface  of  the  membrane.  Mr.  Beck  informs  me  that  he  has  repeatedly  found  the 
membrane  appearinjr  as  if  composed  of  polygonal  scales  or  tables,  and  hence  he  regards  it 
as  an  epithelium.  I have  not  succeeded  in  observing  an  epithelial  structure  in  it. 


BRANCHING  AND  CONJUNCTION  OF  NERVES. 


165 


nate  lights  and  shadows  caused  by  the  successive  bendings  being  seen 
through  the  sheath,  give. rise  to  the  appearance  of  alternate  light  and 
dark  cross  stripes  on  the  funiculi,  or  even  on  larger  cords  consisting 
of  several  funiculi.  On  stretching  the  nerve,  the  fibres  are  straight- 
ened and  the  striped  appearance  is  lost. 

Vessels. — The  blood-vessels  of  a nerve  supported  by  the  neurilemma 
divide  into  very  fine  capillaries,  said  by  Henle  to  measure  in  the 
empty  state  not  moi'e  than  go’ooth  of  an  inch  in  diameter.  These, 
which  are  numerous,  run  parallel  with  the  funiculi,  but  are  connected 
at  intervals  by  short  transverse  branches,  so  as  in  fact  to  form  a net- 
work with  very  long  narrow  meshes. 

Branching  and  Conjunction  of  Nerves. — Nerves  in  their  progress 
very  commonly  divide  ir^to  branches,  and  the  branches  of  different 
nerves  not  unfrequently  join  with  each  other.  As  regards  the  arrange- 
ment of  the  fibres  in  these  cases,  it  is  to  be  observed,  that,  in  the 
branching  of  a nerve,  portions  of  its  fibres  successively  leave  the  trunk 
and  form  branches;  and  that,  when  different  nerves  or  their  branches 
intercommunicate,  fibres  pass  from  one  nerve  to  become  associated 
with  those  of  the  other  in  their  further  progress;  but  in  neither  case 
(Unless  at  their  peripheral  terminations)  is  there  any  such  thing  as  a 
division  or  splitting  of  an  elementary  nerve  fibre  into  two,  or  an  actual 
junction  or  coalescence  of  two  such  fibres  together. 

A communication  between  two  nerves  is  sometimes  effected  by  one 
or  two  connecting  branches.  In  such  comparatively  simple  modes  of 
connexion,  which  are  not  unusual,  both  nerves  commonly  give  and 
receive  fibres;  so  that,  after  the  junction,  each  contains  a mixture  of 
fibres  derived  from  two  originally  distinct  sources.  More  rarely  the 
fibres  pass  only  from  one  of  the  nerves  to  the  other,  and  the  contribu- 
tion is  not  reciprocal.  In  the  former  case  the  communicating  branch 
or  branches  will  of  course  contain  fibres  of  both  nerves,  in  the  latter 
of  one  only. 

In  other  cases  the  branches  of  a nerve,  or  branches  derived  from 
two  or  from  several  diflerent  nerves,  are  connected  in  a more  compli- 
cated manner,  and  form  what  is  termed  a plexus.  In  plexuses,  of 
which  the  one  named  “ brachial”  or  “ axillary,”  formed  by  the  great 
nerves  of  the  arm,  and  the  “lumbar”  and  “sacral,”  formed  by  those 
of  the  lower  limb  and  pelvis,  are  appropriate  examples,  the  nerves  or 
their  branches  join  and  divide  again  and  again,  interchanging  and  in- 
termixing their  fibres  so  thoroughly,  that,  by  the  time  a branch  leaves 
the  plexus,  it  may  contain  fibres  from  all  the  nerves  entering  the 
plexus.  Still,  as  in  the  more  simple  communications  already  spoken 
of,  the  fibres  remain  individually  distinct  throughout. 

Some  farther  circumstances  remain  to  be  noticed  as  to  the  course  of  the  fibres 
in  nerves  and  nervous  plexuses. 

Gerber*  has  described  and  figured  nerve-fibres,  which,  after  running  a certain 
way  in  a nerve,  apparently  join  in  form  of  loops  with  neighbouring  fibres  of  the 
same  funiculus,,  and  proceed  no  further.  Such  loops  might  of  course  be  repre- 
sented as  formed  by  fibres  which  bend  back  and  return  to  the  nervous  centre; 
and  so  Gerber  considers  them.  He  likens  them  to  the  loops  said  to  be  formed 


* Handbuch  der  allgemeinen  Anatomic,  (1840,)  § 267. 


166 


NERVOUS  SYSTEM. 


by  the  fibres  at  the  extremities  or  peripheral  terminations  of  nerves  in  various 
sentient  parts,  and  regards  them  accordingly  as  the  terminations  of  sentient  fibres 
appropriated  to  the  nerve  itself — as  the  nervi  nervorum,  in  short,  on  which  depends 
the  sensibility  of  the  nerve  to  impressions,  painful  or  otherwise,  applied  to  it  else- 
where than  at  its  extremities.  The  whole  matter  is,  however,  involved  in  doubt; 
for,  admitting  the  existence  of  the  loops  referred  to,  which  yet  requires  confirma- 
tion, it  is  not  impossible  that  they  may  be  produced  by  fibres  which  run  back 
only  a certain  way,  and  then,  entering  another  funiculus,  proceed  onwards  to  the 
termination  of  the  nerve.  Again,  it  has  been  supposed,  that,  in  some  instances 
of  nervous  conjunctions,  certain  collections  of  fibres,  after  passing  from  one  nerve 
to  another,  take  a retrograde  course  in  that  second  nerve,  and,  in  place  of  being 
distributed  peripherally  with  its  branches,  turn  back  to  its  root  and  rejoin  the 
cerebro-spinal  centre.  An  apparent  example  of  such  nervous  arches  without 
peripheral  distribution  is  afforded  by  the  optic  nerves,  in  which  various  anato- 
mists admit  the  existence  of  arched  fibres,  that  seem  to  pass  across  the  commis- 
sure between  these  nerves  from  one  optic  tract  to  the  other,  and  to  return  again 
to  the  brain.  These,  however,  are  perhaps  to  be  compared  with  the  commissu- 
ral fibres  of  the  brain  itself,  of  which  there  is  a great  system  connecting  the 
symmetrical  halves  of  that  organ.  But  instances  of  a similar  kind  occurring 
in  other  nerves  have  been  pointed  out  by  Volkmann;*  as  in  the  connexion 
between  the  second  and  third  cervical  nerves  of  the  cat,  also  in  that  of  the 
fourth  cranial  nerve  with  the  first  branch  of  the  fifth  in  other  quadrupeds,  and 
in  the  communications  of  the  cervical  nerves  with  the  spinal  accessory  and  the 
descendens  noni.  But  certain  fibres  of  the  optic  nerves  take  a course  deviating 
still  more  from  that  followed  genet  " they  appear  to  be  continued  across 


nerve  and  eye,  without  being  connected  with  the  brain  at  all,  and  thus  forming 
arches  with  peripheral  terminations,  but  no  central  connexion.  In  looking, 
however,  for  an  explanation  of  this  arrangement,  it  must  be  borne  in  mind  that 
the  retina  contains  nerve-cells  or  vesicles,  like  those  of  the  nervous  centres,  and 
perhaps  the  fibres  referred  to  may  be  intended  merely  to  bring  the  vesicular  mat- 
ter of  the  two  sides  into  relation  independently  of  the  brain. 

Origins  or  Roots  of  the  Nerves. — The  cerebro-spinal  nerves,  as 
already  said,  are  connected  by  one  extremity  to  the  brain  or  to  the 
spinal  cord,  and  this  central  extremity  of  a nerve  is,  in  the  language 
of  anatomy,  named  its  origin  or  root.  In  some  cases  the  root  is  single, 
that  is,  the  funiculi  or  fibres  by  which  the  nerve  arises  are  all  attached 
at  one  spot  or  along  one  line  or  tract;  in  other  nerves,  on  the  con- 
trary, they  form  two  or  more  separate  collections,  which  arise  apart 
from  each  other  and  are  connected  with  diflferent  parts  of  the  nervous 
centre,  and  such  nerves  are  accordingly  said  to  have-  two  or  more 
origins  or  roots.  In  the  latter  case,  moreover,  the  different  roots  of  a 
nerve  may  differ  not  only  in  their  anatomical  characters  and  connex- 
ions, but  also  in  function,  as  is  well  exemplified  in  the  spinal  nerves, 
each  of  which  arises  by  two  roots,  an  anterior  and  a posterior — the 
former  containing  the  motory  fibres  of  the  nerve,  the  latter  the 
sensory. 

The  fibres  of  a nerve,  or  at  least  a considerable  share  of  them,  may 
be  traced  to  some  depth  in  the  substance  of  the  brain  or  spinal  cord, 
and  hence  the  term  “apparent  or  superficial  origin”  has  been  em- 
plo3md  to  denote  the  place  where  the  root  of  a nerve  is  attached  to 
the  surface,  in  order  to  distinguish  it  from  the  “ real  or  deep  origin,” 
which  is  beneath  the  surface  and  concealed  from  view. 

To  trace  the  different  nerves  back  to  their  real  origin,  and  to  de- 


the  commissure  from  the  eyeball 


nerve  of  one  side  to  the  opposite 


* Muller,  Archiv.  (1840)  p.  510. 


ROOTS  OF  THE  NERVES. 


167 


termine  the  points  where  and  the  modes  in  which  their  fibres  are  con- 
nected with  the  nervous  centre,  is  a matter  of  great  difficulty  and  un- 
certainty; and,  accordingly,  the  statements  of  anatomists  respecting 
the  origin  of  particular  nerves  are  in  many  cases  conflicting  and  un- 
satisfactory. Confining  ourselves  here  to  what  applies  to  the  nerves 
generally,  it  may  be  stated,  that  their  roots,  or  part  of  their  roots,  can 
usually  be  followed  for  some  way  beneath  the  surface,  in  form  of  white 
tracts  or  bands  distinguishable  from  the  surrounding  substance ; and 
very  generally  these  tracts  of  origin  may  be  traced  towards  deposits 
of  gray  nervous  matter  situated  in  the  neighbourhood,  such,  for  in- 
stance, as  the  central  gray  matter  of  the  spinal  cord,  the  gray  nuclei 
of  the  pneumogastric  and  glossopharyngeal  nerves,  the  corpora  geni- 
culata,  and  other  larger  gray  masses  connected  with  the  origin  of  the 
optic  nerve.  It  would  further  seem  probable  that  certain  fibres  of  the 
nerve-roots  take  their  origin  in  these  local  deposits  of  gray  matter, 
whilst  others  become  continuous  with  the  white  fibres  of  the  spinal  cord 
or  encephalon,  which  are  themselves  connected  with  the  larger  and 
more  general  collections  of  gray  matter  situated  in  the  interior  or  on 
the  surface  of  the  cerebro-spinal  axis.  As  has  been  already  more  fully 
stated,  (p.  154,)  there  is  a difference  of  opinion  as  to  the  mode  in 
which  the  nerve-fibres  supposed  to  arise  in  the  gray  matter  are  con- 
nected with  its  elements;  some  anatomists  describing  them  as  forming 
loops  or  arches  in  the  gray  matter,  passing  into  it,  as  it  were,  and  re- 
turning, whilst  others  maintain  that  the  fibres  are  prolonged  from  the 
caudate  nerve-cells. 

The  fibres  of  origin  of  a nerve,  whether  deeply  implanted  or  not, 
on  quitting  the  surface  of  the  brain  or  spinal  cord  to  form  the  apparent 
origin  or  free  part  of  the  root,  are  in  most  cases  collected  into  funiculi, 
which  are  each  invested  with  a sheath  of  neurilemma.  This  investment 
is  generally  regarded  as  a prolongation  of  the  pia  mater,  and  in  fact 
its  continuity  with  that  membrane  may  be  seen  very  plainly  at  the 
roots  of  several  of  the  nerves,  especially  those  of  the  cervical  and 
dorsal  nerves  within  the  vertebral  canal,  for  in  that  situation  the  neu- 
rilemma, like  the  pia  mater  itself,  is  much  stronger  than  in  the  cranium. 
The  funiculi,  approaching  each  other  if  originally  scattered,  advance 
towards  the  foramen  of  the  skull  or  spine  which  gives  issue  to  the 
nerve,  and  pass  through  the  dura  mater,  either  in  one  bundle  and  by 
a single  aperture,  or  in  two  or  more  fasciculi,  for  which  there  are  two 
or  more  openings  in  the  membrane.  The  nerve-roots  in  their 
course  run  beneath  the  arachnoid  membrane,  and  do  not  perforate  it 
on  issuing  from  the  cranio-vertebral  cavity ; for  the  loose  or  visceral 
layer  of  the  arachnoid  is  prolonged  on  the  nerve  and  loosely  surrounds 
it  as  far  as  the  aperture  of  egress  in  the  dura  mater,  where,  quitting 
the  nerve,  it  is  reflected  upon  the  inner  surface  of  the  latter  membrane, 
and  becomes  continuous  with  the  parietal  or  adherent  layer  of  the 
arachnoid.  The  nerve,  on  escaping  from  the  skull  or  spine,  acquires 
its  external,  stout,  fibro-cellular  sheath,  which  connects  all  its  funiculi 
into  a firm  cord,  and  then,  too,  the  nerve  appears  much  thicker  than 
before  its  exit.  The  dura  mater  accompanies  the  nerves  through  the 
bony  foramina,  and  becomes  continuous  with  their  external  sheath  and 


1G8 


NERVOUS  SYSTEM. 


(at  the  cranial  foramina)  with  the  pericranium;  but  the  sheath  does 
not  long  retain  the  densely  fibrous  character  of  the  membrane  with 
which  it  is  thus  connected  at  its  commencement. 

The  arrangement  of  the  membranes  on  the  roots  of  certain  of  the  cranial 
nerves  requires  to  be  specially  noticed. 

The  numerous  fasciculi  of  the  olfactory  nerve  pass  through  their  foramina 
almost  immediately  after  springing  from  the  olfactory  bulb,  and  then  also  receive 
their  neurilemma.  The  bulb  itself,  and  intra-cranial  part  of  the  nerve,  which  are 
to  be  regarded  as  being  really  a prolongation  or  lobe  of  the  brain,  are  invested 
externally  by  the  pia  mater,  but  are  not  fasciculated.  The  arachnoid  membrane 
passes  over  the  furrow  of  the  brain  in  which  this  part  of  the  nerve  lies,  without 
affording  it  a special  investment. 

The  optic  nerve  becomes  subdivided  internally  into  longitudinal  fasciculi  by 
neurilemma  a little  way  in  front  of  the  commissure  : on  passing  through  the  optic 
foramen  it  receives  a sheath  of  dura  mater,  ■which  accompanies  it  as  far  as  the 
eyeball.  The  acoustic  nerve  becomes  fasciculated,  receives  its  neurilemma,  and 
acquires  a firm  structure  on  entering  the  meatus  auditorius  internus  in  the  tem- 
poral bone,  towards  the  bottom  of  which  it  presents  one  or  more  small  ganglionic 
swellings  containing  the  characteristic  cells.  Up  to  this  point  it  is  destitute  of 
neurilema,  and  is  of  soft  consistence,  whence  the  name  “ portio  mollis”  applied 
to  it. 

The  larger  root  of  the  fifth  pair  acquires  its  neurilemma  and  fasciculated  cha- 
racter sooner  at  its  circumference  than  in  the  centre,  so  that,  in  the  round  bunch 
of  cords  of  which  it  consists,  those  placed  more  outwardly  are  longer  than  those 
within,  and,  when  all  are  pulled  away,  the  non-fascicular  part  of  the  nerve 
remains  in  form  of  a small  conical  eminence  of  comparatively  soft  nervous 
substance. 

Most  of  the  nerves  have  ganglia  connected  with  their  roots.  Thus, 
the  spinal  nerves  have  each  a ganglion  on  the  posterior  of  the  two 
roots  by  which  they  arise ; and  in  like  manner  several  of  the  cranial, 
viz.,  the  fifth,  seventh,  glosso-pharyngeal,  and  pneumogastric,  are  fur- 
nished at  their  roots,  or  at  least  within  a short  distance  of  their  origin, 
with  ganglia  which  involve  a greater  or  less  number  of  their  fibres,  as 
described  elsewhere  in  the  special  anatomy  of  those  nerves. 

Termination  or  peripheral  extremity  of  nerves. — The  results  of 
modern  microscopic  discovery  seemed  for  a time  to  lead  to  the  conclu- 
sion that  the  fibres  of  nerves  do  not,  strictly  speaking,  end  in  the 
tissues  in  which  they  are  distributed,  but  merely  dip  into  those  tissues, 
as  it  were,  and,  after  forming  slings  or  loops  of  greater  or  less  width, 
return  sooner  or  later  to  the  nervous  trunks.  The  further  progress  of 
inquiry,  has,  however,  failed  to  establish  the  generality  of  this  conclu- 
sion, and  has  even  gone  far  to  disprove  the  existence  of  the  alleged 
mode  of  termination  in  various  cases  in  which  it  had  previously  been 
held  to  take  place;  and  indeed  it  must  be  admitted  that  the  arrange- 
ment of  the  nervous  fibres  at  their  peripheral  extremities  is  still  but 
imperfectly  understood,  as  will  appear  from  the  following  summary  of 
what  is  at  present  known  on  the  subject. 

In  no  case  was  the  termination  of  nerves  by  loops  more  generally  acknowledged 
than  in  voluntary  muscle,  and  accordingly  it  is  so  described  in  the  account  already 
given  of  the  nerves  of  that  tissue  in  the  present  work  '(vol.  i.  p.  320)  : but  certain 
observations  very  recently  made  known  by  Wagner*  are  calculated  to  throw 
considerable  doubt  on  the  opinions  hitherto  received,  especially  when  viewed  in 


• Loc.  cit. 


TERMINATION  OF  NERVES. 


169 


connexion  with  the  results  of  collateral  inquiries  to  be  presently  referred  to,  which 
have  been  made  by  several  observers,  respecting  the  nerves  of  various  other 
textures.  Wagner  states,  that,  in  the  muscles  of  the  frog,  the  tubular  nerve-fibres 
may  be  observed  to  be  at  last  divided  into  fine  branches,  which  appear,  (although 
he  is  not  quite  certain  on  this  point,)  to  perforate  the  sarcolemma  of  the  muscular 
fibres,  and  to  divide  into  still  finer  filaments,  not  more  than  Tvj 57^-0 th  or  7-^ o'o  of  an 

inch  in  size,  that  run  between  the  muscular  fibriUee,  where  they  elude  further 
scrutiny.  The  looped  mode  of  termination  was  described  by  Valentin  as  occur- 
ring in  the  nerves  of  the  iris  and  ciliary  ligament. 

The  mode  of  ultimate  distribution  of  the  nerves  in  the  skin  and  in  analogous 
parts  of  mucous  membrane  endowed  with  a considerable  degree  of  tactile  sensi- 
bility, is  still  a subject  of  much  uncertainty. 

In  the  skin  of  the  frog  the  nerves  break  up  into  branches,  which  become 
smaller  by  repeated  division,  and  are  at  length  reduced  to  fine  bundles  of  only 
two  or  three  fibres  each.  The  branches  frequently  join  and  separate,  and  the 
larger  ones  are  observed  very  generally  to  run  alongside  the  blood-vessels : the 
finest  ramifications  form  at  last  a close  network,  in  which  they  mutually  give  and 
receive  fibres.  As  regards  the  further  disposition  of  the  ultimate  fibres,  Valentin, 
E.  Burdach,  and  others,  state  that  they  merely  pass  from  one  nervous  branch  or 
bundle  to  another,  rarely  running  singly,  and  that  they  do  not  end  in  the  tissue, 
but,  after  coursing  a longer  or  a shorter  way  through  the  plexus,  of  which  they,  in 
fact,  form  the  finest  divisions,  return  sooner  or  later  to  the  larger  branches.  But, 
although  the  arrangement  appears  to  the  eye  such  as  described,  further  inquiries 
have  shown- that  there  is  something  beyond.  Thus,  fibres  have  been  seen  (by 
Todd  and  Bowman)  passing  from  the  plexus  through  the  supeijacent  layers  of 
membrane  towards  the  surface  of  the  skin,  and  not  visibly  ending  in  loops,  but 
becoming  at  last  lost  to  view.  In  the  eyelid  of  the  frog,  also,  in  which  the  plexi- 
form  arrangement  of  the  fine  nervous  branches  is  readily  seen,  Henle  observed 
nerve-fibres  which  ran  singly  a long  way,  and  then  disappeared,  there  being  no 
evidence  that  they  were  continuous  with  others  in  the  form  of  loops;  some 
sdemed  to  end  abruptly,  and  this  appearance,  which  Henle  was  disposed  to 
consider  fallacious,  has  since  been  described  again  by  Hannover,  who  moreover 
saw  other  primitive  fibres  dividing  into  finer  filaments^  which  were  arranged 
into  a plexus,  and  ultimately  eluded  the  sight. 

To  these  examples  must  be  added  the  very  remarkable  observations  of  Schwann 
on  the  terminations  of  the  nerves  in  the  web  or  fin  of  the  tadpole’s  tail.  In  that 
instance,  as  well  as  in  the  mesentery  of  amphibia,  it  appeared  to  Schwann  that 
the  ordinary  primitive  nerve-fibres,  after  separating  from  the  fasciculi,  divided 
into  other  fibres  of  much  smaller  size,  and  that  the  finer  fibres  resulting  from  this 
division,  which  were  destitute  of  white  substance  and  wanted  the  dark  outline, 
here  and  there  presented  little  enlargements  or  nodules,  from  whence,  again, 
delicate  fibres  spread  out  in  various  directions,  and  connected  themselves  in  form 
of  a network.*  Subsequent  observations  made  by  myself,  on  the  nerves  of  the 
tail  of  the  tadpole,  are  confirmatory  of  those  of  Schwann.  The  fine  fibres,  which 
are  derived  from  the  division  of  the  ordinary  ones,  want  the  bold,  dark  outline 
which  usually  marks  the  tubular  fibres ; they  also  present  here  and  there  along 
their  course  elongated  corpuscles  like  cell-nuclei ; and,  from  their  similarity  in 
aspect  to  the  gelatinous  fibres,  it  might  be  supposed  that  they  are  really  prolonged 
from  gelatinous  fibres  mixed  up  with  the  tubular  kind  in  the  nervous  branches; 
there  can  be  no  doubt,  however,  as  to  their  source,  for  fine  tubular  fibres  may  be 
traced,  which  change  their  character  as  they  proceed,  lose  their  dark  outline,  and 
pass  continuously  into  these  pale  nucleiferous  fibres;  moreover,  many  of  the 
decidedly  tubular  fibres  in  this  situation  are  marked  with  nucleus-like  corpuscles.! 
The  tubular  fibres  might  thus  be  represented  as  laying  aside  their  white  substance 
and  dark  outline  before  dividing  or  terminating,  like  those  ending  in  the  Pacinian 

* These  little  radiating  knots,  which  are  supposed  by  Schwann  to  be  the  remnants  of 
cells  from  which  the  fibres  are  developed,  are  not  to  be  confounded  with  the  ramified 
colourless  cells  (resembling  in  figure  branched  pigment  cells)  which  abound  in  the  tissue  in 
which  the  nerves  are  distributed.  I have  never  been  able  to  perceive  any  conne.vion 
between  the  nerve-fibres  and  these  last-mentioned  cells. 

t In  one  instance  it  seemed  to  me  that  a tubular  fibre  divided  into  two  branches. 

15 


VOL.  II. 


170 


JVERVOUS  SYSTEM. 


bodies,  to  be  presently  described  ; but  in  the  present  case  (of  the  growing  tail  of 
the  tadpole)  the  pale  libres  are  in  reality  to  be  considered  as  an  earlier  condition 
of  tubular  fibres  in  progress  of  development.  Schwann,  who  adopts  this  view, 
states  that  the  pale  fibres  are  the  forerunners  of  tubular  fibres,  and  he  conceives  that 
they  are  converted  into  the  latter  by  acquiring  the  white  substance  (medullary 
sheath),  and  with  this  the  dark  outline.  Still,  whether  perfect  or  not,  these  fine 
fibres  must  be  capable  of  receiving  and  conducting  sensorial  impressions  applied 
to  the  decidedly  sentient  membrane  in  which  they  are  distributed. 

The  density  and  opacity  of  the  cutaneous  tissue  in  man  and  quadrupeds  render 
the  investigation  of  the  ultimate  distribution  of  the  cutaneous  nerves  extremely 
difficult.  Nevertheless,  Gerber,  by  boiling  portions  of  skin,  and  then  steeping 
them  in  oil  of  turpentine,  succeeded  in  making  the  tissue  so  transparent,  that  in 
thin  sections  of  it  he  was  able,  as  he  believes,  to  see  the  terminations  of  the 
nerves.  He  describes  the  nerves  as  ending  in  the  less  sensible  parts  of  the  skin 
by  a plexus,  the  ultimate  branches  of  which  consist  of  two  or  more  fibres ; but, 
in  the  more  sensitive  parts,  also  by  loops  of  single  fibres,  often  much  waved  or 
convoluted,  which  rise  from  the  ple.xus  and  enter  the  papillae.  Krause  also  states, 
that,  by  treating  the  human  skin  with  nitric  acid,  he  was  able  to  perceive  that  the 
simple  fibres  into  which  the  nervous  branches  approaching  the  surface  had  divi- 
ded, passed  into  the  papillae,  forming  one  or  sometimes  two  or  three  loops  or 
doublings  in  each ; and  that  often  the  same  fibre  would  ascend  into  and  come 
out  of  several  papillae  in  succession.  On  the  other  hand,  Todd  and  Bowman, 
although  they  saw  bunches  of  loop-like  fibres  in  the  papillae  of  the  tongue,  which 
in  many  respects  resemble  the  cutaneous  papillae,  nevertheless  failed  to  detect 
any  such  loops  in  the  papillae  of  the  skin : they  were  able  to  trace  solitary  2ierve- 
tubules  ascending  a certain  way  into  the  papillae,  and  then  becoming  lost  to  sight, 
either  by  simply  ending,  or  else  by  losing  their  white  substance,  by  which  only 
they  are  distinguishable  from  the  fibres  of  other  tissues  in  this  situation.  Further 
evidence  seems  therefore  desirable,  in  order  to  determine  the  point  with  certainty. 

In  dissecting  the  nerves  of  the  hand  and  foot,  certain  small  oval  bodies,  like 
little  seeds,  are  found  attached  to  their  branches  as  they  pass  through  the  subcu- 
taneous fat  on  their  way  to  the  skin  ; and  it  has  been 
ascertained  that  each  of  these  bodies  receives  a ner- 
vous fibre  which  terminates  within  it.  The  objects 
referred  to  were  more  than  a century  ago  described 
and  figured  by  Vater,*  as  attached  to  the  digital 
nerves,  but  he  did  not  examine  into  their  structure, 
and  his  observation  seems  not  to  have  attracted 
much  notice.  Within  the  last  few  years  their  exist- 
ence has  been  again  pointed  out  by  Cruveilhier  and 
other  French  anatomists,  as  well  as  by  Professor  Pa- 
cini of  Pisa,  who  appears  to  be  the  first  writer  that 
has  given  an  account  of  the  internal  structure  of 
these  curious  bodies,  and  clearly  demonstrated  their 
essential  connexion  with  the  nervous  fibres.  The 
researches  of  Pacini  have  been  followed  up  by  Henle 
and  Kdlliker,t  who  named  the  corpuscles  after  the 
Italian  savant;  and  to  their  memoir,  as  well  as  to  the 
article  “ Pacinian  Bodies,”  by  Mr.  Bowman,  in  the 
“ Cyclopaedia  of  Anatomy,”  the  reader  is  referred 
A.  Nerve  from  the  finger,  natu- ^ details  that  cannot  be  conveniently  introduced 
ral  size;  showing  Ihe  racinian 
corpuscles. 


[Fig.  322. 


here. 


b'.  Ditto,  magnified  2 diameters;  The  little  bodies  in  question  (fig.  322')  are,  as  al- 
showing  their  different  size  and  peady  said,  attached  in  great  numbers  to  the, branches 
shape.— Todd  and  Bowman.]  nerves  of  the  hand  and  foot,  and  here  and 

there  one  or  two  are  found  on  other  cutaneous  nerves.  They  have  been  disco- 
vered also  within  the  abdomen  on  the  nerves  of  the  solar  plexus,  and  they  are 
nowhere  more  distinctly  seen  or  more  conveniently  obtained  for  examination, 

* Abr.  'Vater,  D'ss.  de  Consensu  Partium  Corp.  hum.;  'Vitemb.  1741,  (recus  in  Halleri 
Disp.  Anat.  Select,  tom.  ii.)  Ejusd.  Museum  Anatomicum  ; Helmst,  1750. 
t Uebcr  die  Pacinisclien  KOrpcrchen  ; Zurich,  1844. 


PACINIAN  CORPUSCLES. 


171 


than  in  the  mesentery  and  omentum  of  the  cat,  between  the  layers  of  which  they 
exist  abundantly.  They  are  found  in  the  fcetus,  and  in  individuals  of  all  ages. 
The  figure  of  these  corpuscles  is  oval,  somewhat  like  that  of  a grain  of  wheat, — 
regularly  oval  in  the  cat,  but  mostly  curved  or  reniform  in  man,  and  sometimes 
a good  deal  distorted.  Their  mean  size  in  the  adult  is  from  .p'^th  to  of  an 
inch  long,  and  from  ^B^th  to  of  an  inch  broad.  They  have  a whitish,  opa- 
line aspect ; in  the  cat’s  mesentery  they  are  usually  more  transparent,  and  then  a 
white  line  may  be  distinguished  in  the  centre.  A slender  stalk  or  peduncle  attaches 
the  corpuscle  to  the  branch  of  nerve  with  which  it  is  connected.  The  peduncle 
consists  of  a single  tubular  nerve-fibre  ensheathed  in  filamentous  cellular  tissue, 
with  one  or  more  fine  blood-vessels ; and  it  joins  the  corpuscle  at  or  near  one 
end,  and  conducts  the  nerve-fibre  into  it.  The  little  body  itself,  examined  under 
the  microscope,  is  found  to  have  a beautiful  lamellar  structure  (fig.  323).  It 

[Fig.  323.  Fig.  324. 


Fig.  323,  represents  the  Pacinian  corpuscle,  from  the  mesentery  of  the  cat ; intended  to  show 
the  general  construction  of  these  bodies.  The  stalk  and  body,  the  outer  and  the  inner  syste  n of 
capsules,  with  the  central  cavity,  are  seen.  a.  Arterial  twig,  ending  in  capillaries,  which  lorin 
loops  in  some  of  the  intercapsular  spaces,  and  one  penetrates  to  the  central  capsule,  b.  The 
fibrous  tissue  of  the  stalk  prolonged  from  the  neurilemma,  n.  Nerve  tube  advancing  to  the  cen- 
tral capsule,  there  losing  its  white  substance,  and  stretching  along  the  axis  to  the  opposite  end, 
where  it  is  fixed  by  a tubercular  enlargement. 

Fig.  324.  A.  Termination  of  the  stalk,  and  commencement  of  the  central  cavity,  n.  Nerve-tube 
advancing  to  the  central  capsule,  and  there  suddenly  losing  its  white  substance  and  becoming 
pale.  a.  Artery  ending  in  capillaries;  one  of  which  enters  an  intercapsular  space,  the  other  ad- 
vances with  the  nerve  into  the  inner  capsule,  b.  Conical  tube  which  receives  the  stalk ; the 
fibrous  tissue  of  the  stalk  is  not  represented.  c.  Wall  of  this  tube,  continuous  with  the  successive 
capsules,  here  seen  in  sections,  d.  Corpuscle  of  the  capsular  wall.  e.  More  spherical  granular 
corpuscle,  of  which  a few  only  exist. 

B.  Distal  end  of  the  central  cavity,  n.  Pale  nerve  advancing  along  the  axis,  to  be  fixed  by  a 
swollen  part  at  the  further  end.  c.  Wall  of  the  central  cavity,  receiving  the  insertion  of  some  of 
the  neighbouring  capsules,  here  a little  separated  from  each  other  by  water,  o.  Intercapsular 
ligament  of  Pacini,  continued  a little  way  towards  the  surface. 

c.  Two  varieties  of  bifid  extremity  of  nerve,  attached  to  the  distal  extremity  of  the  central 
cavity, — All  magnified  320  diameters. — Todd  and  Bowman.] 


172 


NERVOUS  SYSTEM. 


consists,  in  fact,  of  numerous  concentric  membranous  capsules  incasing  each 
other  like  the  coats  of  an  onion,  with  a small  quantity  of  transparent  and  probably 
albuminous  fluid  lodged  between  them,  the  innermost  containing  a cylindrical 
cavity  filled  with  the  same  kind  of  fluid,  into  which  the  nerve-fibre  passes.  The 
number  of  capsules  is  various;  from  forty  to  sixty  may  be  counted  in  large  cor- 
puscles. The  series  immediately  following  the  central  or  median  cavity,  and 
comprehending  about  half  the  entire  number,  are  closer  together  than  the  more 
exterior  ones,  seeming  to  form  a system  by  themselves,  which  gives  rise  to  a 
white  streak  often  distinguishable  by  the  eye  along  the  middle  of  the  corpuscles. 
Outside  of  all,  the  corpuscle  has  a coating  of  ordinary  cellular  tissue.  The  cap- 
sules, at  least  the  more  superficial  ones,  consist  each  of  an  internal  layer  of  lon- 
gitudinal and  an  external  of  circular  fibres,  which  resemble  the  white  fibres,  of 
areolar  and  fibrous  tissue,  with  cell-nuclei  attached  here  and  there  on  the  inner 
layer,  and  a few  branched  fibres  of  the  yellow  or  elastic  kind  running  on  the 
outer.  The  nerve-fibre,  conducted  along  the  centre  of  the  stalk,  enters  the  cor- 
puscle, and  passes  straight  into  the  central  cavity,  at  the  further  end  of  which  it 
terminates. 

The  fibrous  neurilemma  surrounding  the  nerve-fibre  in  the  peduncle  accompa- 
nies it  also  in  its  passage  through  the  series  of  capsules,  gradually  decreasing  in 
thickness  as  it  proceeds,  and  ceasing  altogether  when  the  nerve  has  reached  the 
central  cavity.  According  to  Pacini,  with  whom  Reichert  agrees  in  this  particu- 
lar, the  neurilemma  forms  a series  of  concentric  cylindrical  layers,  which  succes- 
sively become  continuous  with,  or  rather  expand  into  the  capsules^,  the  innermost,  of 
course,  advancing  farthest.  Others  suppose  that  the  capsules  are  all  successively 
perforated  by  a conical  channel,  which  gives  passage  to  the  nerve  with  its  neuri- 
lemma, but  at  the  same  time  has  its  owm  proper  wall,  round  which,  on  the  outside, 
the  capsules  are  attached.  Whichever  view  may  be  correct,  the  capsules  are, 
as  it  were,  strung  together  where  the  nerve  passes  through  them,  and  each  inter- 
capsular  space,  with  its  contained  fluid,  is  shut  off  from  the  neighbouring  ones. 
The  nerve-fibre,  the  disposition  of  which  must  now  be  noticed,  is  single  as  it  runs 
along  the  peduncle,  unless  where  the  latter  supports  two  corpuscles ; it  retains  its 
dark  double  contour  until  it  reaches  the  central  cavity,  where,  diminished  in  §ize, 
and  freed  from  its  neurilemma,  it  becomes  somewhat  flattened,  and  presents  the 
appearance  either  of  a pale,  finely  granular,  and  very  faintly  outlined  band  or 
stripe,  little  narrower  than  the  previous  part  of  the  fibre,  or  of  a darker  and  more 
sharply  defined  narrow  line ; differing  thus  in  appearance  according  as  its  flat 
side  or  its  edge  is  turned  towards  the  eye.  The  pale  aspect  which  the  fibre  pre- 
sents in  the  centre  of  the  corpuscle,  has  with  some  probability  been  ascribed  to 
its  losing  the  white  substance  or  medullary  sheath  on  entering  the  cavity ; Henle 
and  Kolliker,  however,  think  that  it  is  more  likely  the  result  merely  of  a diminution 
in  size  together  with  a certain  degree  of  flattening.  It  sometimes  happens  that 
the  fibre  regains  its  original  magnitude  and  double  contour  for  a short  space,  and 
changes  again  before  it  terminates  ; this  is  especially  liable  to  occur  while  it  passes 
through  a sharp  flexure  in  a crooked  central  cavity.  The  fibre  ends  by  a sort  of 
knob  at  the  further  extremity  of  the  median  cavity,  which  is  often  itself  somewhat 
dilated.  In  many  cases,  the  fibre,  before  terminating,  divides  into  two  branches, 
as  represented  in  figure  c ; a division  into  three  has  been  observed,  but  this  is 
very  rare.  In  case  of  division  of  the  fibre,  the  cavity  is  generally,  but  not  inva- 
riably, divided  in  a corresponding  measure,  and  the  inner  set  of  capsules  present 
a figure  in  keeping  with  it.  It  is  worthy  of  remark,  that  the  nerve-fibre  in  its 
course  along  the  cavity  runs  almost  exactly  in  the  axis,  and  it  maintains  this 
position  even  when  passing  through  the  abrupt  flexures  of  an  irregularly  shaped 
cavity.  It  sometimes  happens  that  a fibre  passes  quite  through  one  corpuscle 
and  terminates  in  a second,  resuming  its  original  size  and  dark  outline  while 
passing  from  the  one  to  the  other.  Pappenheira  states  that  he  has  seen  a nerve- 
fibre  going  through  two  Pacinian  bodies  without  terminating  in  either,  but  re- 
turning again  to  the  parent  nerve  in  the  form  of  a loop.  Other  varieties  occur, 
for  an  account  of  which  the  reader  is  referred  to  the  several  authorities  already 
mentioned.  A little  artery  enters  the  Pacinian  bodies  along  with  the  nerve,  and 
soon  divides  into  capillary  branches,  which  pierce  the  parietes  of  the  passage 
and  run  up  between  the  capsules.  Mr.  Bowman  finds  that  they  then  form  loops, 


TERMINAL  FIBRES. 


173 


and  return  by  a similar  route  into  a vein  corresponding  to  the  artery : he  states  also 
that  a single  capillary  usually  accompanies  the  nerve  as  far  as  the  central  capsule, 
and  passes  some  way  on  its  wall,  sometimes  in  a spiral  direction. 

Nothing  positive  is  known  concerning  the  purpose  in  the  animal  economy 
which  these  curious  appendages  of  the  nerves  are  destined  to  fulfil.  After  pass- 
ing in  review  various  conjectures  which  naturally  suggest  themselves,  Pacini, 
and,  after  him,  Henle  and  Kolliker,  looking  to  a certain  correspondence  in  struc- 
ture between  these  little  bodies  and  the  electric  organs  of  the  torpedo  and  other 
similarly  endowed  fishes,  are  disposed  to  think  that  the  most  promising  hypo- 
thesis that  can  in  the  mean  time  be  adopted  is  that  they  are  analogous  in  function 
with  these  electric  organs.  It  must  be  confessed,  however,  that  any  experiments 
that  have  been  instituted  for  the  purpose  have  as  yet  altogether  failed  to  elicit 
proof  that  the  Pacinian  bodies  develope  electricity.  Cruveilhier  and  others  sup- 
pose that  they  are  morbid  or  accidental  productions,  probably  resulting  from 
pressure  applied  to  the  nerves ; but  their  constant  presence  (at  least  in  certain  re- 
gions in  the  body)  in  perfectly  healthy  individuals,  at  all  periods  of  life,  and  even 
in  the  foetus,  and,  above  all,  their  regular  and  elaborate  internal  structure,  forbid 
us  to  regard  them  as  the  result  of  accident  or  disease. 

The  fine  branches  of  nerves  which  enter  the  cavities  of  the  teeth  form  plexuses 
in  the  vascular  pulp,  and  Valentin  describes  the  fibres  as  at  last  ending  by  loops; 
according  to  Purkinje  they  end  in  form  of  pencils  at  the  summit  of  the  pulp. 

It  has  already  been  incidentally  mentioned,  that  looped  nerve-fibres  have  been 
seen  in  the  papillse  of- the  tongue.  On  the  mucous  membrane  of  the  nose  the 
branches  of  the  olfactory  nerves  have  a plexiform  arrangement,  but  the  manner 
in  which  their  fibres  terminate  has  not  been  satisfactorily  determined. 

The  fibres  of  the  optic  nerve,  on  entering  the  eyeball,  spread  out  in  the  retina. 
They  become  attenuated,  and,  according  to  Todd  and  Bowman,  lose  their  white 
substance  and  double  contour,  and  collectively  assume  a gray  aspect.  The  most 
recent  inquirers,  such  as  Hannover,  describe  them  as  neither  dividing,  nor  join- 
ing, nor  forming  loops ; these  fibres  eventually  become  lost  to  view,  and  it  has 
not  yet  been  ascertained  how  they  end.  The  fine  lamina  of  the  retina  formed  by 
the  fibres  is  covered  both  externally  and  internally  with  a layer  of  cells,  which 
are  most  probably  of  the  same  nature  as  the  cells  or  ganglion  globules  found  in 
the  nervous  centres.  For  further  details,  the  reader  is  referred  to  the  special  de- 
scription of  the  eye. 

The  terminal  fibres  of  the  auditory  nerve  seem  to  be  differently  arranged  in  the 
different  parts  of  the  complex  apparatus  in  which  it  is  distributed.  On  the  mem- 
branous ampullae  of  the  semicircular  canals  they  form  loops ; but  free  ends  may 
also  be  seen  among  the  loops,  according  to  the  testimony  of  more  than  one  ob- 
server. In  the  vestibular  sac  and  common  sinus,  part  of  the  fibres  proceed  to 
the  pulverulent  calcareous  matter  contained  in  those  sacculi,  and  terminate 
amongst  it  in  a mode  not  yet  precisely  ascertained ; other  fibres  spread  out  on  the 
wall  of  the  sacs,  apparently  losing  their  white  substance,  and  becoming  con- 
nected with  a layer  of  dark  nucleated  cells.  Various  observers  profess  to  have 
seen  looped  nerve-fibres  on  the  lamina  spiralis  of  the  cochlea.  Some  have  ob- 
served free  ends  as  well  as  loops ; others,  again,  could  not  discover  terminal 
loops.  Todd  and  Bowman  describe  the  fibres  as  being  collected  into  small, 
tapering,  terminal  fasciculi,  in  which  it  is  very  difficult  to  distinguish  the  disposi- 
tion of  the  individual  tubules.  The  fibres  are  here  mixed  with  nuclei,  but  retain 
their  white  substance. 

As  connected  with  the  present  subject,  I cannot  avoid  adverting  to  the  remark- 
able fact  discovered  by  Savi,  respecting  the  terminal  fibres  of  the  nerves  distri- 
buted on  the  horizontal  membranous  partitions  or  diaphragms  in  the  electric 
apparatus  of  the  torpedo,  namely,  that  these  fibres  or  elementary  tubules  actu- 
ally bifurcate  or  divide  dichotomously  into  branches  possessing  the  same  tubular 
character  which  inosculate  together  so  as  to  form  a network.  Wagner,  who  has 
since  examined  this  structure,  recognises  the  division  of  the  tubular  fibres,  but 
denies  the  netlike  conjunctions;  he  states  that  the  nervous  tubules  divide  at 
first  not  dichotomously,  but  into  several  branches  which  divaricate  from  the  same 
point,  and  then, . after  repeatedly  bifurcating,  become  greatly  reduced  in  size, 
lose  their  dark  outline  and  double  contour,  and  at  length  can  be  no  longer  distin- 

15* 


174 


NERVOUS  SYSTEM. 


guished  from  the  tissue  in  which  they  lie.  Robin*  states  that  he  has  observed 
the  division  as  well  as  the  reticular  inosculations  of  the  terminal  nerve-tubules  in 
an  organ  which  has  been  lately  discovered  in  the  tail  of  various  common  species 
of  rays,  and  which,  in  respect  of  intimate  structure  at  least,  offers  considerable 
resemblance  to  the  electric  apparatus  of  the  torpedo.  I have  myself  seen  the 
division  of  the  tubular  nerve-fibres  (though  I cannot  say  how  they  terminate)  in 
tlie  above-mentioned  organ,  which,  it  may  be  well  to  add,  was  discovered  by  Dr. 
Stark,  of  Edinburgh,  in  1844,  and  regarded  by  him  as  an  electric  apparatus.! 

From  the  foregoing  account  of  the  peripheral  extremities  of  the 
nerves,  it  will  be  apparent,  first,  that  the  disposition  of  their  elemen- 
tary fibres  in  terminal  loops  or  in  terminal  plexuses,  through  which 
they  return  again  towards  the  parent  trunks,  is  by  no  means  general ; 
that,  as  far  as  known,  they  more  commonly  end  by  simply  truncated 
or  slightly  swollen  extremities,  as  in  the  instance  of  those  entering  the 
Pacinian  bodies,  or  become  gradually  lost  to  the  sight  in  the  surround- 
ing tissue,  usually  after  considerable  reduction  in  size,  and  after  laying 
aside  their  dark  outline,  probably  from  privation  of  their  white  sub- 
stance. That,  even  where  apparently  terminal  loops  are  observed,  it 
is  difficult  to  say  whether  these  may  not,  in  some  cases,  be  caused  by 
serpentine  windings  of  the  fibres  previous  to  their  actual  termination, 
which  may  itself  be  hidden  from  view.  Secondly,  that  elementary 
nerve-fibres,  although,  as  far  as  is  known,  they  keep  entire  and  dis- 
tinct in  their  course  along  the  nerves,  do  in  various  instances  actually 
divide  into  branches,  and  in  some  cases  unite  or  inosculate  with  each 
other,  in  approaching  their  termination.  Thirdly,  that  in  certain 
cases  the  fibres  of  nerves  come  into  near  relation  at  their  peripheral 
extremities  with  cells  resembling  the  nerve-cells  of  the  brain  and 
ganglia.J 

Differences  of  cerebrospinal  nerves. — It  remains  to  notice  the  dif- 
ferences which  have  been  observed  among  the  cerebro-spinal  nerves 
in  regard  to  the  size  of  their  fibres,  and  the  proportionate  amount  of 
the  diflerent  kinds  of  fibres  which  they  respectively  contain. 

As  already  stated,  both  tubular  and  gelatinous  fibres  exist  in  cerebro-spinal 
nerves,  and  those  of  the  tubular  kind  differ  greatly  from  each  other  in  size ; but 
some  anatomists  consider  that  two  different  average  sizes  prevail  among  the 
tubular  fibres,  scarcely,  if  at  all,  connected  by  intermediate  gradations;  they 
accordingly  distinguish  two  varieties  of  thern,  characterized  by  their  size ; and 
Volkmann  and  Bidder,  as  will  be  more  fully  explained  in  treating  of  the  sympa- 
thetic nerve,  are  further  of  opinion  that  the  small  kind  are  a system  of  nervous 
fibres  derived  from  the  ganglia.  Be  this  as  it  may,  the  authors  just  named  have 
bestowed  much  pains  in  endeavouring  to  arrive  at  an  approximate  estimate  of 
the  relative  amount  of  the  large  and  the  small  fibres  in  different  nerves,  and  the 
following  are  the  more  important  results  of  their  researches : — 

1 . The  nerves  of  voluntary  muscles  have  very  few  small  fibres,  usually  in  not 
larger  proportion  than  about  one  to  ten. 

2.  In  the  nerves  of  involuntary  muscles,  whether  derived  immediately  from  the 
cerebro- spinal  system  or  from  the  sympathetic,  the  small  fibres  eminently  pre- 
ponderate, being  about  a hundred  to  one. 

* Annales  des  Sc.  Nat.,  Mai,  1847. 

t Magazine  of  Natural  History,  vol.  xv.  p.  121. 

X It  may  not  be  out  of  place  here  to  remark,  that  M.  Quatrefages  describes  the  cutane- 
ous nerves  of  the  singularly  organized  fish  named  the  Amphioxus  or  Branchiostoma,  as 
finally  dividing  into  excessively  delicate  homogeneous  fibres,  each  of  which  terminates 
singly  in  a little  oval  body  below  the  fine  integument.  In  the  figure  which  accompanies 
his  description,  the  small  terminal  bodies  referred  to  appear  not  unlike  oval  cells. 


SYMPATHETIC  NERVE.  I75 

3.  The  nerves  going  to  the  integuments  have  always  many  small  fibres,  at 
least  as  many  small  as  large. 

4.  Nerves  of  sentient  parts  of  mucous  membranes  have  from  five  to  twenty 
times  more  small  fibres  than  large  ; in  mucous  membranes  possessing  little  sen- 
sibility the  nerves  are  made  up  chiefly  of  small  fibres.  The  nerves  distributed 
in  the  pulp  of  the  teeth  consist  principally  of  large  fibres. 

It  is  plain,  however,  that  Volkmann  and  Bidder  must  have  reckoned  in  with 
their  small  fibres  more  or  fewer  of  the  gelatinous  sort,  so  that  the  proportion 
assigned  to  the  small  fibres  in  their  estimate  must  be  taken  as  including  gelati- 
nous as  well  as  tubular  fibres ; and  this  agrees  with  the  observation  previously 
made  by  Remak,  that  many  more  gelatinous  fibres  are  contained  in  the  cuta- 
neous than  in  the  muscular  nerves.  The  roots  of  the  spinal  nerves  contain  fine 
fibres,  but  according  to  Remak  only  in  very  small  proportion;  Volkmann  and 
Bidder  state  that  in  man  the  anterior  roots  contain  proportionally  more  large 
fibres  than  the  posterior.  In  almost  all  nerves  the  fibres  diminish  in  size  as  they 
approach  their  termination. 

The  fibres  of  the  optic  nerve  for  the  most  part  resemble  the  white  fibres  of  the 
brain,  and  readily  become  varicose.  . The  same  is  true  of  the  acoustic  nerve, 
from  its  origin  to  its  entrance  into  the  internal  auditory  foramen,  where  it  be- 
comes fasciculated ; also  of  the  intracranial  part  of  the  olfactory,  which,  however, 
contains  in  addition  gray  matter  and  nerve-cells.  The  branches  of  the  olfactory 
in  the  nose  are  almost  wholly  made  up  of  fibres  bearing  nuclei,  and  having  all 
the  outward  characters  of  the  gelatinous  fibres,  like  which,  also,  they  cohere  or 
cling  fast  together  in  the  bundles  which  they  form.  Some  branches  seem  to  con- 
sist entirely  of  such  fibres ; others  contain  a few  tubular  fibres  intermixed, 
which,  however,  may  perhaps  be  derived  from  the  nasal  branches  of  the  fifth 
pair.  'I’his  peculiarity  of  the  branches  of  the  olfactory  nerve,  distinguishing  it 
so  much  from  other  cerebral  nerves,  was,  as  far  as  I know,  first  distinctly  pointed 
out  by  Todd  and  Bowman,  although  it  seems  not  altogether  to  have  escaped  the 
notice  of  preceding  anatomists,  of  Valentin,  for  instance,  who  compares  the 
branches  of  the  olfactory  to  the  nervi  modes  of  the  sympathetic. 

OF  THE  SYMPATHETIC  OR  GANGLIONIC  NERVE. 

This  name  is  commonly  applied  to  a nerve  or  system  of  nerves  pre- 
sent on  both  sides  of  the  body,  and  consisting  of  the  following  parts, 
viz.: — 1.  A series  of  ganglia  placed  along  the  spinal  column  by  the 
side  of  the  vertebrae,  connected  with  each  other  by  an  intermediate 
nerve-cord,  and  extending  upwards  to  the  base  of  the  skull  and  down- 
wards as  far  as  the  coccyx.  This  principal  chain  of  ganglia,  with  the 
cord  connecting  them,  forms  what  is  often  named  the  trunk  of  the 
sympathetic.  2.  Communicating  branches,  which  connect  these  gan- 
glia or  the  intermediate  cord  with  all  the  spinal  and  several  of  the 
cranial  nerves.  3.  Primary  branches  passing  off  from  the  ganglionic 
chain  or  trunk  of  the  nerve,  and  either  bestowing  themselves  at  once, 
and  generally  in  form  of  plexuses,  on  the  neighbouring  blood-vessels, 
glands,  and  other  organs,  or,  as  is  the  case  with  the  greater  number, 
proceeding  in  the  first  instance  to  other  ganglia  of  greater  or  less  size 
(sometimes  named  praevertebral),  situated  in  the  thorax,  abdomen,  and 
pelvis,  and  usually  collected  into  groups  or  coalescing  into  larger  gan- 
glionic masses  near  the  roots  of  the  great  arteries  of  the  viscera.  4. 
Numerous  plexuses  of  nerves,  sent  off  from  these  visceral  or  prrever- 
tebral  ganglia  to  the  viscera,  usually  creeping  along  the  branches  of 
arteries,  and  containing  in  various  parts  little  ganglia  disseminated 
among  them.  Some  of  these  plexuses  also  receive  contributions  from 
spinal  or  cerebral  nerves,  by  means  of  branches  which  immediately 


176 


NERVOUS  SYSTEM. 


proceed  to  them  without  previously  joining  the  main  series  of 
ganglia. 

Structure  of  the  sym'pathetic  nerve. — The  nervous  cords  of  the  sym- 
pathetic consist  of  tubular  fibres,  and  of  gelatinous  fibres  mixed  with 
a greater  or  less  amount  of  filamentous  cellular  tissue,  and  enclosed  in 
a common  external  fibro-cellular  sheath.  The  tubular  fibres  differ 
greatly  from  each  other  in  thickness.  A few  are  of  large  size,  ranging 
from  5u'ooth  to  of  an  inch  ; but  the  greater  number  are  of  much 

smaller  dimensions,  measuring  from  about  ^-jx^oth  to  -450x5'^ 
in  diameter,  and,  though  having  a well-defined  sharp  outline,  for  the 
most  part  fail  to  present  the  distinct  double  contour  seen  in  the  larger 
and  more  typical  examples  of  the  tubular  fibre.  The  gelatinous  fibres 
present  the  characters  already  described  as  pertaining  to  them. 

The  more  gray-looking  branches  or  bundles  of  the  sympathetic  con- 
sist of  a large  number  of  the  gelatinous  fibres  mixed  with  a few  of  the 
tubular  kind;  the  whiter  cords,  on  the  other  hand,  contain  a propor- 
tionally large  amount  of  tubular  fibres,  and  fewer  of  the  gelatinous; 
and  some  parts  of  the  nerve,  gray  fasciculi,  and  white  fasciculi,  re- 
spectively constituted  as  above  described,  run  alongside  of  each  other 
in  the  same  cords  for  a considerable  space  without  mixing.  This 
arrangement  may  be  seen  in  some  of  the  branches  of  communication 
with  the  spinal  nerves,  in  the  trunk  or  cord  which  connects  together 
the  principal  chain  of  ganglia,  and  in  the  primary  branches  proceeding 
from  thence  to  the  viscera.  In  the  last-mentioned  case  the  different 
fasciculi  get  more  mixed  as  they  advance,  but  generally  it  is  only 
after  the  white  fasciculi  have  passed  through  one  or  more  ganglia  that 
they  become  thoroughly  blended  with  the  gray;  and  then,  too,  the 
nervous  cords  receive  a large  accession  of  gelatinous  fibres,  (appa- 
rently derived  from  the  ganglia,)  which  are  mixed  up  with  the  rest, 
and  take  off  more  and  more  from  their  whiteness. 

Eegarding  the  nature  of  the  gelatinous  fibres,  there  is,  as  has  already  been  re- 
marked, a wide  difference  of  opinion,  for  several  anatomists  of  reputation  deny 
that  they  are  nervous  fibres  at  all : it  becomes  necessary,  therefore,  before  pro- 
ceeding further,  to  consider  briefly  this  question. 

Those  who  deny  the  nervous  nature  of  these  fibres,  rely  chiefly  on  the  differ- 
ence in  aspect  and  anatomical  characters  between  them  and  undoubted  nervous 
fibres,  and  account  for  their  presence  in  the  nerves  by  referring  them  to  the  class 
of  enveloping  structures;  maintaining,  in  short,  that  they  are  nothing  but  fibres 
of  cellular  tissue  imperfectly  developed  or  otherwise  modified,  and  that  they  serve 
merely  as  a sort  of  neurilemma  for  the  tubular  or  true  nervous  fibres.  To  this  it 
may  be  replied,  in  the  first  place,  that  the  large  proportionate  amount  of  gela- 
tinous fibres  in  many  branches  of  the  sympathetic  nerve,  and  their  varying 
arrangement  in  respect  of  the  tubular  fibres  associated  with  them,  do  not  accord 
with  the  idea  of  an  enveloping  tissue.  Next,  as  regards  discrepancy  in  structure 
and  outward  aspect,  we  may  call  to  mind  the  instance  of  the  striped  and  plain 
muscular  fibres,  as  satisfactorily  proving  that  textures  differing  widely  in  ana- 
tomical characters  may  yet  fundamentally  agree  in  function  and  vital  endow- 
ments. Moreover,  it  is  not  correct  to  say  that  the  gelatinous  fibres  have  the 
characters  of  cellular  tissue  either  perfectly  or  imperfectly  formed ; it  would  be 
much  nearer  the  truth  to  compare  their  appearance,  as  some  have  done,  to  that 
of  the  tubular  nervous  fibres  in  an  early  stage  of  the  development,  although  in 
saying  this  it  is  not  meant  that  they  are  actually  unfinished  nervous  fibres.  If 
there  be  transitions,  as  is  said,  between  the  gelatinous  fibres  and  the  filaments  of 
cellular  tissue,  transitions,  too,  it  may  be  replied,  are  not  wanting  between  them 


GELATINOUS  FIBRES. 


177 


and  the  tubular  nerve-fibres.  Thus,  Purkinje  has  described  small-sized  pale 
fibres  bearing  nuclei,  and  thus  in  so  far  agreeing  with  gelatinous  fibres,  which 
were,  nevertheless,  filled  with  oleaginous  fluid  contents  like  the  tubular ; and  so 
slight,  indeed,  would  seem  to  be  the  gradations  with  which  the  two  kinds  of 
fibres  pass  into  each  other,  that  Volkmann  and  Bidder,  both  excellent  observers, 
have  been  taxed  with  unwittingly  reckoning  gelatinous  fibres  among  those  which 
they  consider  as  the  true  nervous  fibres,  while  professing  to  distinguish  between 
them.  Again,  an  undoubted  nervous  tubule  may  in , some  part  of  its  course 
assume  characters  approaching  closely  to  those  of  the  fibres  in  dispute.  Thus, 
it  is  no  uncommon  thing  for  a tubular  fibre  of  the  most  typical  form,  in  approach- 
mg  its  termination,  to  decrease  in  size,  lose  its  double  contour,  and  present  the 
faint  outline  and  finely  granular  aspect  of  a gelatinous  fibre  : we  have  seen  that 
this  change  always  occurs  when  a fibre  enters  a Pacinian  body ; and  in  the  tad- 
pole’s tail,  as  already  described,  nervous  tubules  are  continued  into  fibres  which 
are  marked  with  nuclei,  and  wholly  agree  in  appearance  with  the  gelatinous 
fibres ; these  are  probably  immature,  it  is  true,  but  yet  they  are  distributed  to  a 
sentient  part,  and  are  capable  of  conducting  sensorial  impressions.  It  would 
seem  as  if  the  difference  in  more  obvious  characters  between  the  different  parts 
of  the  fibres  in  these' cases,  and  perhaps  also  that  between  nerve-fibres  in  general, 
depended  mainly  on  their  respective  size,  and  on  the  different  proportion  of  their 
white  substance,  as  well  as  on  the  presence  or  absence  of  nucleiform  corpuscles. 
Were  further  proof  wanting  that  a pale  faintly  granular  aspect,  want  of  dark  out- 
line, cohesion  with  its  neighbours,  and  abundant  nuclei  along  its  course,  ought 
not  to  be  considered  as  depriving  a fibre  of  its  nervous  character,  we  need  only 
refer  to  the  structure  of  the  nasal  part  of  the  olfactory  nerve,  already  pointed  out. 

But  it  is  further  objected,  that,  whilst  tubular  fibres  have  been  seen  to  arise 
from  ganglionic  cells,  those  of  the  gelatinous  sort  are  unconnected  with  these 
bodies,  and  appear  to  proceed  from  their  inclosing  capsules, — a difference  both 
distinguishing  them  from  nervous  fibres,  and  indicative  of  their  enveloping  or 
neurilemmatic  character.  Without,  however,  admitting  or  denying  the  force  of 
this  objection,  were  it  founded  in  fact,  it  must  be  remembered  that  it  rests  prin- 
cipally on  negative  evidence  directly  opposed  by  the  positive  observations  of 
Remak  and  Hannover;  and  the  strenuous  denial  by  Valentin  and  other  highly 
respectable  authorities,  of  the  connexion  even  of  the  tubular  fibres  with  ganglionic 
cells, — a connexion  which  has  been  so  decidedly  established  by  subsequent  ob- 
servations,— ought  to  render  us  distrustful  of  an  objection  resting  on  negative  evi- 
dence in  a case  so  nearly  analogous. 

In  the  last  place,  it  is  asserted  that  the  gelatinous  fibres  do  not  continue  in  the 
nerves  as  far  as  their  extremities,  and  that  they  are  accordingly  wanting  in  the 
branches  of  nerves  distributed  in  the  coats  of  the  intestines,  and  in  various  other 
parts  supplied  by  the  sympathetic.  But  this  statement  is  inconsistent  with  the 
observations  both  of  Remak*  and  of  Beck  ;f  and  the  latter  observer  maintains 
even  that  very  fine  bundles  of  the  sympathetic  sometimes  consist  solely  of  gela- 
tinous fibres. 

We  have  next  shortly  to  consider  the  relation  between  the  sympa- 
thetic and  the  cerebro-spinal  system  of  nerves.  On  this  important 
question  two  very  different  opinions  have  long  existed,  in  one  modifi- 
cation or  another  among  anatomists.  1.  According  to  one,  which  is 
of  old  date,  but  which  has  lately  been  revived  and  ably  advocated  by 
Valentin,  the  sympathetic  nerve  is  a mere  dependency,  offset,  or  em- 
branchment of  the  cerebro-spinal  system  of  nerves,  containing  no  fibres 
but  such  as  centre  in  the  brain  and  cord,  although  it  is  held  that  these 
fibres  are  modified  in  their  motor  and  sensory  properties  in  passing 
through  the  ganglia  in  their  way  to  and  from  the  viscera  and  involun- 
tary organs,  2.  According  to  the  other  view,  the  sympathetic  nerve 
(commonly  so  called)  not  only  contains  fibres  derived  from  the  brain 


De  Syst.  Nerv.  Struct.,  p.  25. 


t Phil.  Trans.,  1846,  p.  216. 


178 


NERVOUS  SYSTEM. 


and  cord,  but  also  proper  or  intrinsic  fibres  which  take  their  rise  in 
the  ganglia;  and  in  its  communications  with  the  spinal  and  cranial 
nerves,  not  only  receives  from  these  nerves  cerebro-spinal  fibres,  but 
iiuparts  to  them  a share  of  its  own  proper  ganglionic  fibres,  to  be  in- 
corporated in  their  branches  and  distributed  peripherally  with  them. 
Therefore,  according  to  this  latter  view,  the  sympathetic  nerve,  com- 
monly so  called,  though  not  a mere  offset  of  the  cerebro-spinal  nerves, 
yet,  receiving  as  it  does  a share  of  their  fibres,  is  not  wholly  inde- 
pendent; and,  for  a like  reason,  the  cerebro-spinal  nerves  (as  com- 
monly understood)  cannot  be  considered  as  constituted  independently 
of  the  sympathetic  ; in  short,  both  the  cerebro-spinal  and  the  sympa- 
thetic are  mixed  nerves,  that  is,  the  branches  of  either  system  consist 
of  two  sets  of  fibres  of  different  and  independent  origin,  one  connected 
centrally  with  the  brain  and  cord,  the  other  with  the  ganglia.  Hence, 
if  we  look  to  the  central  connexion  of  their  fibres  as  the  essential 
ground  of  distinction  among  nerves,  the  cerebro-spinal  system  of  nerves 
might,  strictly  speaking,  be  considered  as  consisting  of  and  compre- 
hending all  the  fibres  having  their  centre  in  the  cerebro-spinal  axis, 
whether  these  fibres  run  in  the  nerves  usually  denominated  cerebral 
and  spinal,  or  are  distributed  to  the  viscera  in  the  branches  of  the 
nerve  usually  named  the  sympathetic;  and,  on  the  same  ground,  the 
sympathetic  or  ganglionic  system,  strictly  and  properly  so  called, 
would  consist  of  and  comprehend  all  the  fibres  connected  centrally 
w'ith  the  ganglia,  wherever  such  fibres  exist  and  into  whatever  com- 
binations they  enter,  whether  proceeding  to  the  viscera  or  distributed 
peripherally  with  the  nerves  of  the  body  generally  ; the  ganglia  on  the 
roots  of  the  spinal  and  cerebral  nerves,  with  the  nerve-fibres  emanating 
from  them,  being  reckoned  into  this  system,  as  well  as  those  usually 
denominated  sympathetic.  While  ready,  however,  to  acquiesce  in  the 
justice  of  the  above  distinction,  we  do  not  mean  to  employ  the  terms 
already  in  use  in  a sense  different  from  that  which  is  currently  re- 
ceived. 

In  endeavouring  to  decide  between  the  two  views  above  stated,  it  maybe  first 
observed  that  the  existence  in  the  sympathetic  nerve  of  fibres  connected  centrally 
with  the  cerebro-spinal  axis  is  proved  not  only  by  tracing  bundles  of  fibres  from 
the  roots  of  the  spinal  nerves  along  the  communicating  branches  and  into  the 
sympathetic,  but  by  the  pain  or  uneasy  sensations  which  arise  from  disease  or 
disturbance  of  organs,  such  as  the  intestines,  supplied  exclusively  by  what  are 
considered  branches  of  the  sympathetic,  and  by  experiments  on  living  or  recently 
killed  animals,  in  which  artificial  irritation  of  the  roots  of  the  spinal  nerves,  or  of 
various  parts  of  the  cerebro-spinal  centre,  caused  movements  of  the  viscera. 

This  fact,  it  is  evident,  accords  with  both  of  the  above-mentioned  opinions  re- 
specting the  constitution  of  the  sympathetic ; but  it  may  be  further  shown  that 
this  nerve  contains  fibres  which  arise  from  the  ganglia  and  take  a peripheral 
course,  so  that  the  second  of  the  twm  opinions  approaches  nearer  to  the  truth. 
In  support  of  this  assertion  w^e  may  adduce  the  actual  observation  of  nerve-fibres 
proceeding  from  the  nerve-cells  of  the  ganglia, — a fact  which  may  now'  be  con- 
sidered as  established,  and  which  would  of  itself  be  sufficient  to  settle  the  ques- 
tion, unless  we  suppose,  with  Wagner,  that  each  of  these  ganglionic  fibres  has 
its  root  in  the  cerebro-spinal  centre,  and  is  merely  connected  with,  or,  as  it  were, 
interrupted  by,  a ganglionic  globule  in  its  course;  in  which  case,  however,'such 
fibres  would  still  be  peculiar  and  different  from  those  fibres  w’hich  are  uncon- 
nected with  ganglia.  But  there  are  independent  grounds  for  believing  that  more 


RELATIONS  OF  SYMPATHETIC  AND  SPINAL  NERVES. 


179 


fibres  pass  out  of  the  sympathetic  ganglia  than  can  possibly  he  derived  from  the 
brain  and  cord.  This  seems  to  follow  from  a comparison  of  the  aggregate  size 
of  the  branches  issuing  from  these  ganglia  with  that  of  all  the  branches  which 
can  be  supposed  to  enter  them.  To  explain  this,  however,  we  must  first  consider 
the  mode  of  communication  between  the  sympathetic  and  spinal  nerves. 

The  branches  of  communication  which  pass  between  the  ganglia  or  gangliated 
cord  of  the  S3rmpathetic  and  the  spinal  nerves,  are  connected  with  the  anterior 
and  gTcater  branch  of  each  of  the  latter  nerves,  a little  in  advance  of  the  spinal 
ganglion ; and  at  the  point  of  connexion  the  communicating  branch  in  most  cases 
divides  into  two  portions,  one,  central,  running  towards  the  roots  of  the  spinal 
nerve  and  the  spinal  cord,  the  other,  peripheral,  taking  an  outward  course  along 
with  the  anterior  branch  of  the  spinal  nerve,  with  which  it  becomes  incorporated 
and  distributed.  It  can  scarcely  be  doubted  that  the  central  portion,  whilst  it 
may  contain  fibres  sent  by  the  sympathetic  to  the  spinal  nerves  or  to  the  spinal 
cord,  must  necessarily  contain  all  those  which  proceed  from  the  cord  to  the  sym- 
pathetic, and  that,  on  the  other  hand,  the  peripheral  division  must  consist  of  fibres 
immediately  proceeding  from  the  sympathetic  and  distributed  peripherally  with 
the  spinal  nerve.  It  is  further  observed,  that,  in  some  of  the  junctions  with  the 
spinal  nerves,  the  central  and  peripheral  divisions  of  the  communicating  branch 
are  about  equal  in  size,  and  that  in  others  the  central  part  is  greater  than  the 
peripheral,  whilst  m others,  again,, the  peripheral  prevails  over  the  central.  Now, 
in  an  animal  such  as  the  frog,  in  which  the  spinal  nerves  are  of  small  size  and  few 
in  number,  it  is  possible,  with  the  aid  of  the  microscope,  to  compare  by  mea- 
surement the  central  and  peripheral  divisions  of  the  communicating  branch  in  all 
the  communications  between  the  sympathetic  and  the  spinal  nerves,  or  even  to 
count  the  fibres  when  the  branches  are  very  fine ; and  by  such  a comparison 
Volkmann  and  Bidder  have  shown,  that,  after  making  all  reasonable  deductions 
and  allowances,  the  whole  amount  of  the  fibres,  or  at  least  the  aggregate  bulk  of 
the  fasciculi,  which  obviously  pass  from  the  sympathetic  and  run  outwards  with 
the  spinal  nerves,  considerabl}'  exceeds  that  of  the  central  fasciculi  which  must 
contain  the  fibres  contributed  to  the  sympathetic  from  the  cerebro-spinal  system  ' 
and  if  to  these  peripheral  fibres  we  add  the  branches  distributed  to  the  -viscera,  it 
seems  plain  that  more  fibres  must  proceed  from  the  ganglia  than  can  possibly  be 
supposed  to  enter  them  from  the  spinal  nerves  or  spinal  cord,  and  that  conse- 
quently the  ganglia  must  themselves  be  centres'  in  which  nerve-fibres  take  their 
rise.  It  is  worthy  of  remark,  that,  in  the  frog,  according  to  the  observations  of 
the  anatomists  just  named,  the  central  division  of  the  communicating  cord  greatly 
exceeds  the  peripheral  in  the  connexions  with  the  upper  spinal  nerves,  but  that 
lower  dowii  it  gradually  diminishes,  absolutely  as  well  as  in  comparison  with  the 
peripheral,  and  at  length  disappears  altogether,  so  that  the  fasciculi  connected 
with  the  8th  and  9th  spinal  nerves  are  entirely  peripheral  in  their  course.  ■ 

Another  circumstance  still  remains  to  be  noticed  respecting  the  communica- 
tions of  the  sympathetic  and  spinal  nerves.  It  has  been  long  known  that  in  most 
of  these  communications  there  are  usually  two  connecting  cords  passing  between 
the  sympathetic  and  the  spmal  nerve ; and  it  has  been  remarked  also  by  various 
observers,  that  these  cords  contain  gray  as  well  as  white  fasciculi.  More  recently, 
however,  Todd  and  Bowman  have  called  attention  to  the  fact  that  one  of  the  two 
connecting  cords  is  altogether  of  the  gray  kind,  consisting  of  gelatinous  fibres, 
with,  as  usual,  a very  few  white  or  tubular  fibres  mixed  with  them ; and  this 
observation  has  since  been  confirmed  by  Beck.  The  other  cord  either  is  entirely 
white,  or,  more  commonly,  is  made  up  of  a white  and  a gray  portion  running 
alongside  each  other.  It  seems  highly  probable  that  the  white  cords  and  the 
white  fasciculi  of  the  mixed  cords  contain  the  cerebro-spinal  fibres  which  the 
spinal  nerves  contribute  to  the  sympathetic,  and  that  the  gray  cords  and  fasciculi 
are  contributions  from  the  sympathetic  to  the  spinal  nerves.  In  corroboration  of 
this  view,  Mr.  Beck  observes  that  the  gray  cords  on  leaving  the  ganglia  give 
small  branches  to  the  neighbouring  vessels,  and  are  reduced  in  size  before  joining 
the  spinal  nerves.  Another  interesting  fact  respecting  these  communications  has 
been  pointed  out  jby  the  last-named  observer,  somewhat  similar  to  that  previously 
noticed  in  the  frog,  namely,  that,  whilst  the  gray  and  white  connecting  cords  are 
in  the  thorax  of  nearly  equal  size,  the  gray  one  relatively  increases  lower  down, 


180 


NERVOUS  SYSTEM. 


and  in  the  pelvis  constitutes  the  sole  communication  between  the  sacral  ganglia 
of  the  sympathetic  and  the  spinal  nerves,  the  white  branches  from  the  latter  to 
the  S}'mpathetic  passing  over  the  sacral  ganglia  without  joining  them,  to  enter  the 
sympathetic  plexuses  sent  to  the  pelvic  viscera. 

The  tubular  fibres  of  each  white  communicating  fasciculus  can  be  traced  back 
to  both  the  anterior  and  the  posterior  root  of  the  spinal  nerve,  and  gelatinous 
fibres  from  the  gray  fasciculus  may  be  traced  up  into  the  anterior  root,  and  as  far 
as  the  ganglion  of  the  posterior  root,  which  root  has  also  gelatinous  fibres  above 
the  ganglion.  Whether  these  central  gelatinous  fibres  proceed  from  the  sympa- 
thetic to  the  spinal  cord  (possibly  to  be  distributed  to  its  vessels),  or  are  sent  from 
the  cord  and  spinal  ganglia  to  the  sympathetic,  or  pass  both  ways,  is  as  yet  un- 
certain. 

As  to  the  further  progress  of  the  cerebro-spinal  fibres  conveyed  to  the  sympa- 
thetic by  the  communicating  branches,  Valentin  has  endeavoured  to  show,  that, 
after  joining  the  main  gangliated  cord  or  trunk  of  the  sympathetic,  they  all  take 
a downward  direction,  and,  after  running  through  two  or  more  of  the  ganglia, 
pass  off  in  the  branches  of  distribution,  leaving  the  trank  considerably  lower 
down  than  the  point  where  they  joined  it.  He  conceives  that  this  arrangement, 
which  he  calls  “lex  progressus,”  is  proved  by  experiments  on  animals,  in  which 
he  found,  that,  on  irritating  different  parts  pf  the  cerebro-spinal  axis,  as  well  as 
different  branches  of  nerves,  the  visceral  moverrients  which  followed  bore  a 
relation  to  the  point  irritated,  which  corresponded  with  the  notion  of  such  an 
arrangement.  Volkmann  and  Bidder,  on  the  other  hand,  endeavour  to  show  that 
this  opinion  cannot  be  reconciled  with  the  observed  anatomical  disposition  of  the 
fibres ; nor  will  the  experimental  evidence  in  its  favour  apply  to  the  upper  part 
of  the  sympathetic,  where,  as  Valentin  himself  admits,  motorial  fibres  must  be 
supposed  to  run  in  an  upward  direction,  to  account  for  the  contraction  of  the  pupil 
which  follows  irritation  of  the  cervical  part  of  the  sympathetic,  unless,  indeed,  we 
suppose  that  the  movement  in  this  case  is  reflex. 

From  what  has  been  stated,  it  seems  reasonable  to  conclude  that 
nerve-fibres  take  their  rise  in  the  ganglia  both  of  the  cerebro-spinal 
and  sympathetic  nerves,  and  are  in  both  kinds  of  nerves  mixed  with 
fibres  of  cerebral  or  spinal  origin;  that  the  ganglia  are  nervous  centres 
which  probably  receive  through  afferent  fibres  impressions  of  which 
we  are  unconscious  and  reflect  these  impressional  stimuli  upon  efferent, 
or  motor  fibres;  that  perhaps,  even,  certain  motorial  stimuli  emanate 
from  them,  the  movements  excited  by  or  through  the  ganglia  being 
always  involuntary,  and  affecting  chiefly  the  muscular  parts  of  the 
viscera,  the  sanguiferous,  and  perhaps  the  absorbent  vessels;  and  that, 
in  fine,  the  chief  purpose  served  in  the  animal  economy  by  the  ganglia 
and  the  gangliolnic  nerve-fibres,  whether  existing  in  acknowledged 
branches  of  the  sympathetic,  or  contained  in  other  nerves,  is  to  govern 
the  involuntary,  and,  for  the  most  part,  imperceptible  movements  of 
nutrition,  in  so  far  at  least  as  these  movements  are  not  dependent  on 
the  brain  and  spinal  cord. 

Among  various  physiologists  of  consideration,  who  adopt  this  view 
in  a more  or  less  modified  shape,  some  are  further  of  opinion  that  the 
fibres  of  ganglionic  origin  differ  in  structure,  size,  and  other  physical 
characters,  from  those  which  arise  in  the  cerebro-spinal  axis.  Thus, 
Remak  considers  the  ganglionic  fibres  to  be  exclusively  of  the  kind 
above  described  under  the  name  of  gelatinous  fibres,  and  these  he  ac- 
cordingly proposed  to  distinguish  by  the  name  of  “organic,”  from  the 
tubular,  which  he  regarded  as  cerebro-spinal  fibres.  Volkmann  and 
Bidder,  on  the  other  hand,  rejecting  the  organic  fibres  of  Remak, 
denying  to  them  indeed  the  character  of  nervous  elements  altogether, 


VITAL  PROPERTIES  OF  THE  NERVOUS  SYSTEM.  181 

endeavour  to  show  that  the  true  ganglionic  fibres  are  identical  with 
the  smaller  variety  of  tubular  fibres,  which  especially  abound  in  the 
branches  of  the  sympathetic — fibres  which  they  hold  are  characterized 
by  small  size  and  by  other  peculiarities  already  mentioned.  They 
contend,  that,  wherever  these  smaller  fibres  occur,  whether  in  the 
sympathetic  or  in  the  branches  or  the  roots  of  the  spinal  or  cerebral 
nerves,  they  are  derived  from  the  ganglia,  whilst  the  larger-sized 
tubular  fibres,  in  the  sympathetic  as  well  as  in  the  spinal  nerves,  are 
of  cerebro-spinal  origin.  As  regards  this  question,  I must  confess, 
that,  although  there  is  sufficient  ground  to  admit  the  existence  of  fibres 
centering  in  the  ganglia,  as  well  as  of  others  which  arise  from  the 
cerebro-spinal  axis,  there  does  not  seem  to  me  to  be  conclusive  evi- 
dence in  favour  of  the  opinions  either  of  Remak  or  of  Volkmann  and 
Bidder,  as  to  peculiar  anatomical  characters  being  distinctive  of  the 
fibres  of  different  origin;  and,  for  aught  that  has  been  proved  to  the 
contrary,  all  three  varieties  of  fibres  spoken  of,  large  tubular,  small 
tubular,  and  gelatinous,  may  arise  both  in  the  cerebro-spinal  axis  and 
in  the  ganglia ; although  it  is  certainly  true,  that  the  two  latter  kinds 
largely  predominate  in  the  sympathetic,  and  abound  in  other  nerves, 
or  branches  of  nerves,  which  appear  to  receive  large  contributions 
from  ganglia. 

VITAL  PUOPERTIES  OF  THE  NERVOUS  SYSTEM. 

The  fibres  of  nerves  are  endowed  with  the  property  of  transmitting 
impressions,  or  the  effect  of  impressions,  from  the  point  stimulated 
towards  their  central  or  their  peripheral  extremities.  One  class  of 
fibres  conduct  towards  the  nervous  centres,  and  are  named  “ afferent,” 
their  impressions  being  “ centripetal another  class  of  fibres  conduct 
towards  their  distal  extremities,  which  are  distributed  in  moving  parts, 
and  these  fibres  are  named  “ efferent,”  whilst  their  impressions  are 
“ centrifugal.”  Impressions  propagated  centrally  along  the  nerves  to 
the  brain  give  rise  to  sensations,  varying  according  to  the  nerve  im- 
pressed, and  the  objective  cause  of  the  impression : stimuli  transmitted 
outwardly,  on  the  other  hand,  are  conveyed  to  muscles,  and  excite 
movements.  Motorial  stimuli  thus  passing  along  efferent  nervous 
fibres  may  emanate  from  the  brain,  as  in  voluntary  and  emotional 
movements,  or  possibly  from  some  other  central  part,  as  in  the  case  of 
certain  involuntary  motions ; or  such  stimuli  may  be  applied  in  the 
first  instance  to  afferent  fibres,  by  these  conducted  to  the  brain  or  some 
other  central  organ,  and  then  “ reflected”  by  the  central  organ  to 
efferent  fibres,  along  which  they  are  propagated  to  the  muscle  or 
muscles  to  be  moved ; and  in  this  case  the  intervention  of  the  central 
organ  may  give  rise  to  sensation  or  not,  the  difference  in  this  respect 
probably  depending  on  the  part  of  the  nervous  centre  where  the  re- 
flexion takes  place. 

The  property  of  conducting  a stimulus  or  propagating  its  effects  in 
a determinate  direction,  belongs  to  the  fibres  of  the  nerves,  and  in  all 
probability  also  to  the  fibrous  part  of  the  nervous -centre,  while  it  is 
probable  that  to  the  gray  matter  of  the  central  organs,  and  especially 
to  its  cells  or  vesicles,  is  assigned  the  office  of  receiving  impressions 

VOL.  II.  16 


182 


NERVOUS  SYSTEM. 


conveyed  from  wilhout,  and  presenting  them  to  the  conscious  mind, — 
of  mediating  between  the  mind  and  the  efferent  fibres  in  excitation  of 
the  latter  by  mental  stimuli  (as  in  voluntary  and  emotional  acts),  of 
transferring  to  efferent  fibres  stimuli  conducted  to  the  centre  by  affe- 
rent fibres  in  the  production  of  reflex  movements,  and,  possibly,  of 
originating  purely  corporeal  stimuli  in  certain  involuntary  motions. 
Many  physiologists  suppose,  that,  in  addition  to  these  endowments,  the 
nerves  have  a peculiar  power  of  controlling  and  regulating  the  mole- 
cular changes  and  chemical  actions  which  occur  in  nutrition  and  in 
other  allied  processes  ; but  it  may  be  fairly  questioned,  whether  the 
effect  justly  attributable  to  the  nerves  in  such  cases,  is  not  produced 
merely  through  the  influence  which  they  exert  over  the  motions  of  the 
minute  vessels  and  contractile  tissues  concerned  in  the  processes 
referred  to. 

The  properties  above  mentioned,  of  the  nerves  and  nervous  centres, 
have  been  commonly  ascribed  to  a peculiar  force  developed  in  the 
nervous  system,  which  has  received  the  names  of  “ nervous  force,” 
“ nervous  principle,”  “ nervous  influence,”  and  “ vis  nervosa”  (in  the 
largest  sense  of  that  term)  ; and  whilst  some  physiologists  consider 
that  force  as  a species  of  agency  altogether  peculiar  to  living  bodies, 
others  have  striven  to  identify  it  with  some  of  the  forces  known  to  be 
in  operation  in  inanimate  nature.  Not  a few  of  the  latter  have  re- 
garded the  nervous  agency  as  identical  with  electricity  in  some  of  its 
modifications,  whilst  others,  acknowledging  truly  that  electricity  is  a 
powerful  stimulant  of  the  nerves,  and,  as  such,  eminently  calculated 
to  set  in  play  the  nervous  force,  and  admitting  that  the  two  have  some 
characters  in  common,  nevertheless  maintain  that  there  is  quite  suffi- 
cient difference  in  their  modes  of  manifestation  to  mark  them  as 
distinct. 

The  greater  number  of  nerves  possess  both  afferent  and  efferent 
fibres,  and  are  named  compound  or  moto-sensory,  inasmuch  as  they 
minister  both  to  sensation  and  motion.  In  such  compound  nerves  the 
two  kinds  of  fibres  are  mixed  together  and  bound  up  in  the  same 
sheaths;  but  in  the  most  numerous  and  best-known  examples  of  this 
class,  the  afferent  and  efferent  fibres,  though  mixed  in  the  trunk  and 
branches  of  the  nerves,  are  separated  at  their  roots.  This  is  the  case 
in  the  spinal  nerves  : these  have  two  roots,  an  anterior  and  posterior, 
both  for  the  most  part  consisting  of  many  funiculi,  and  the  posterior 
passing  through  a ganglion  with  which  the  fibres  of  the  anterior  root 
have  no  connexion.  Now  it  has  been  ascertained  by  appropriate 
experiments  on  animals,  that  the  anterior  root  is  efferent  and  contains 
the  motor  fibres,  and  that  the  posterior  is  afferent  and  contains  the 
sensory  fibres.  The  fifth  pair  of  cranial  nerves  has  a sensory  root 
furnished  with  a ganglion,  and  a motor  root,  like  the  spinal  nerves. 
The  glosso-pharyngeal  and  pneumogastric  nerves  are  also  decidedly 
compound  in  nature;  they  are  also  provided  with  ganglia  at  their 
roots,  which  involve  a greater  or  less  number  of  their  fasciculi;  but  it 
has  not  yet  been  satisfactorily  determined  whether  in  these  nerves  the 
fibres  which  have  different  properties  are  collected  at  the  roots  into 
separate  bundles,  nor  how  they  are  respectively  related  to  the  ganglia. 


DEVELOPMENT  OF  NERVES. 


183 


The  sympathetic,  as  already  stated,  contains  both  afferent  and  efferent 
fibres. 

Simple  nerves  are  such  as  contain  either  afferent  or  efferent  fibres 
only.  The  olfactory,  auditory,  and  optic  are  simple  afferent  and 
sensory  nerves.  The  third,  fourth,  and  sixth,  the  facial,  the  spinal 
accessory  and  hypoglossal  nerves,  are  generally  regarded  as  examples 
of  simple  motor  nerves ; there  is  reason  to  believe,  at  least,  that  they 
are  simple  and  motor  in  their  origin,  or  as  far  as  their  proper  fibres  are 
concerned,  and  that  the  sensibility  evinced  by  some  of  them  in  their 
branches  is  owing  to  sensory  fibres  derived  from  other  nerves  which 
join  them  in  their  progress. 


DEVELOPMENT  OF  NERVES. 

Schwann  found  that,  in  the  foetal  pig,  three  inches  long,  the  commencing  nerves 
consisted  of  a granular  matter  indistinctly  arranged  in  pale,  longitudinal,  coherent 
fibres,  with  cell-nuclei  contained  in  or  attached  to  them.  Though  he  has  not  been 
able  to  trace  their  earliest  stages,  he  infers,  from  the  analogy  of  the  muscular 
tissue,  that  these  fibres  are  formed  by  the  coalescence  of  ceUs  whose  nuclei 
remain,  and  accordingly  supposes  that  they  are  tubes  filled  with  finely  granular 
matter  (fig.  325).  In  a somewhat  more  advanced  stage  these  pale  fibres  lose 
their  granular  aspect,  and  acquire  the  dark  contour, — in  short,  put  on  the  cha- 
racters of  ordinary  tubular  fibres ; and  many  of  them  may  be  seen  which  have 
undergone  this  alteration  in  a part  of 


their  length,  whilst  the  remaming 
part  is  still  in  its  primitive  condition, 
(fig.  325,  c,  d).  The  pale  fibre  is 
supposed  to  acquire  dark  contours  in 
consequence  of  the  formation  of  the 
“ white  substance”  or  “ medullary 
sheath but  the  mode  in  which  this 
substance  is  added  to  the  pale  fibre 
is  uncertain.  Schwann  is  inclined  to 
think  that  it  is  formed  as  a secondary 
deposit  on  the  internal  surface  of  the 
tubular  membrane,  which  he  sup- 
poses to  exist  in  the  pale  fibre  as  a 
tube  formed  by  the  coalesced  walls 
of  the  primary  cells,  and  that  the 


Fig.  325. 


Various  stages  of  the  development  of  nerve  ; — a. 


granular  matter  contained  in  the  pale  Detached  fibre  c Nucleated 

g,  . j - u ■ ■ fiere  in  the  lower  part  of  which,  d,  the  white 

fibre  remains  and  forms  the  primi-  substance  of  Schwann  has  begun  to  be  deposited, 
tive  band”  or axis.”  Most  of  the  e.  Nucleus  in  a more  fully-formed  fibre  between  the 
nuclei  disappear,  but  here  and  there  white  substance  and  tubular  membrane.  /.  Dis- 
one  maybe  seen  on  a tubular  nerve-  tubular  membrane,  the  contained  matter 

fibre,  situated-  according  to  Schwann,  gwen  way.-(After  Schwann.) 

within  the  tubular  membrane,  between  it  and  the  white  substance,  as  represented 
in  fig.  325,  e.  When  first  formed,  the  fibres  are  of  comparatively  small  size. 

In  growing  parts  of  the  embryo  which  extend  themselves  outwards,  the  more 
distant  portion  of  the  nerves,  like  that  of  other  continuous  structures,  must  be 
the  last  formed;  and  in  the  tadpole’s  tail  Schwann  observed  that  the  fibres  of  the 
more  remote  and  growing  nervous  branches  are  smaller  and  devoid  of  the  dark 
contour,  but  are  a continuation  of  fibres  (of  earlier  and  older  branches)  which  possess 
that  character ; so*that  the  deposition  of  white  substance  seems  to  advance  along 
the  fibres  in  a peripheral  direction,  the  part  which  is  nearer  the  centre  and  begins 
earlier  to  be  formed  being  also  first  perfected.  As  mentioned  in  a former  page 
(169),  little  angular  knots  are  observed  in  the  tadpole’s  tad,  where  several  of  these 
pale  fibres  meet  together;  and  these  Schwann  supposes  to  be  remnants  of  forma- 
tive cells  which  had  branched  out  and  united  with  neighbouring  cells  to  form 
the  reticular  nerve-fibres.  Kblliker,  who  has  lately  investigated  the  develop- 
ment of  the  tissues  in  batrachian  larvse,  is  also  of  opinion  that  the  nervous 


184 


NERVOUS  SYSTEM. 


fibres  are  formed  by  the  junction  of  ramified  cells;  he,  however,  further  concludes 
from  his  observations,  that  the  pale  fibres  which  first  appear  enlarge,  that  fine 
tubular  fibres  are  then  developed  in  their  substance,  either  singly  or  in  slender 
fasciculi  of  two  or  three,  and  that  the  latter  fibres  at  first  end  abruptly,  but  even- 
tually form  loops. 

As  to  the  formation  of  the  nerve-cells  found  in  the  gray  matter  of  the  brain, 
spinal  cord,  and  ganglia,  but  very  little  is  known.  Valentin  conceives  that  they 
are  formed  round  other  cells  which  serve  them  as  nuclei,  their  granular  contents 
being  first  deposited,  and  afterwards  their  inclosing  cell-wall.  Others  suppose 
that  they  are  developed  from  nuclei  like  ordinary  cells,  and  then  acquire  their 
peculiar  contents.  The  nucleus-like  bodies  and  the  pellucid  cells  of  different 
sizes  found  in  the  cortical  gray  matter  of  the  brain,  have  been  supposed  to  be 
successive  conditions  of  the  larger  granular  cells  in  progress  of  development ; 
and  some  physiologists  think  it  not  improbable  that  a constant  succession  of  these 
cells  is  produced  to  take  the  place  of  others  that  are  destroyed  and  consumed 
after  fulfilling  their  office. 

The  divided  ends  of  a nerve  that  has  been  cut  across  readily  reunite,  and  in 
process  of  time  true  nerve-fibres  are  formed  in  the  cicatrix,  and  restore  the 
continuity  of  the  nervous  structure.  The  conducting  property  of  the  nerve,  as 
regards  both  motion  and  sensation,  is  eventually  re-established  through  the  re- 
united part» 


NERVOUS  SYSTEM. 


CEEEBRO-SPINAL  AXIS. 

The  nervous  system  consists  of  two  parts — a central  part,  which  in- 
cludes the  brain  and  spinal  cord,  and  is  named  the  cerebro-spinal  axis, 
and  a peripheral  part,  which  comprises  all  the  nerves  in  the  body. 
The  anatomy  of  the  nerves,  which  again  are  subdivided  into  a cerebro- 
spinal and  a sympathetic  system,  will  be  subsequently  treated  of, 
whilst  the  present  section  will  be  devoted  to  a description  of  the  cen- 
tral portion  of  the  nervous  system. 

The  cerebro-spinal  axis  is  contained  partly  within  the  cavity  of  the 
cranium,  and  partly  within  the  vertebral  canal ; it  is  symmetrical  in 
its  form  and  structure  throughout,  consisting  of  a right  and  a left  half, 
which  correspond  in  every  particular,  and  are  joined  together  along 
the  middle  line  by  fibres  of  nervous  substance,  which  pass  across  the 
longitudinal  fissures  existing  between  them.  These  connecting  fibres 
form  the  commissures  of  the  brain  and  spinal  cord. 

Enclosed  within  the  skull  and  the  vertebral  canal,  the  cerebro-spinal 
axis  is  protected  by  the  bony  walls  of  those  two  cavities ; but  it  is  also 
surrounded  by  three  membranes,  which  afford  it  additional  protection 
and  support,  and  are  subservient  to  its  nutrition.  These  envelopes, 
which  will  be  described  hereafter,  are,  a dense  fibrous  membrane 
named  the  dura  mater,  a serous  membrane  called  the  arachnoid,  and 
a highly  vascular  membrane  named  the  pia  mater. 

The  cerebro-spinal  axis  is  divided  by  anatomists  into  the  encephalon 
(Jv,  xecpaXii,  the  head),  the  enlarged  upper  part  contained  within  the 
cranium,  and  the  spinal  cord,  contained  within  the  spinal  canal.  The 
encephalon  is  again  divided  into  the  cerebrum,  or  brain  proper ; the 
cerebellum,  little  brain,  or  after-brain ; the  tuber  annulare,  or  pons 
Varolii,  and  the  medulla  oblongata.  It  should  be  remarked,  that  the 
term  brain,  in  a general  sense,  is  commonly  applied  to  the  entire 
encephalon,  but  that  it  also  has  a limited  application  to  the  cerebrum 
only. 

WEIGHT  OF  THE  ENCEPHALON. 

The  chief  sources  of  information  on  this  subject  are  the  tables  published  by  Dr. 
Sims,*  Dr.  Clendinnmg,t  Tiedemann,$  and  Dr.  John  Reid.^  The  following  table 
is  deduced  from  their  observations.  The  weights  given  by  Tiedemann  have  been 
converted  into  ounces  avoirdupois,  the  weight  employed  by  the  three  British  ob- 

* Sims ; Medico-Chirurg.  Trans.,  vol.  xix.,  pp.  353-7. 

t Clendinning;  Medico-Chirurg.  Trans.,  vol.  xxi.,  pp.  59-68. 

t Tiedemann;  Das  Him  des  Negers,  Heidelberg,  1837,  pp.  6,  7. 

§Reid;  London  and  Edinburgh  Monthly  Journal  of  Medical  Science,  April,  1843, 
p.  298,  &c. 


16* 


186 


CEREBRO-SPINAL  AXIS. 


servers.  All  instances  of  fractional  parts  of  ounces  are  classed  with  the  next 
highest  integral  number,  so  that  the  term  50  oz.,  for  example,  includes  all  cases 
of  brains  weighing  more  than  49  oz.,  but  not  exceeding  50.  From  the  tables  of 
Dr.  Sims  and  Dr.  Clendinning  those  cases  have  been  rejected  in  which  cerebral 
disease  is  said  to  have  existed. 

TABLE  I. 


Males,  aged  21  years  and  upwards.  Females,  aged  21  years  and  upwards. 


Number  of  brains 

Number  of  brains 

at  each  weight 

3 

at  each  weight 

.£3 

o 

observed  by 

A 

o 

Claasification 

observed  by 

Classification 

0> 

into  three 

‘S 

V 

into  three 

> 

bt  in  oz. 
pois. 

.5 

‘S 

0 

cd 

a 

number 

weight. 

groups  to  show 
the  prevailing 
weight, 

o .2 

.a  A 

fcXJ 

a 

•a 

d 

d 

§ 

a 

number 

weight, 

groups,  to  show 
the  prevailing 
weights 

a 

0> 

5 

Sims. 

1 

'O 

Reid. 

o 

irt 

d 

<i> 

o 

Sims. 

o 

P 

12 

‘3 

o 

H 

34 







1 

1 

31 

_ 





1 

1 1 

37 



2 



— 

2 

32 

1 





1 

38 

1 

— 



— 

1 

1—1 

35 



2 





2 

m ( from  -V  g 

39 



3 



1 

4 

« f from  ■> 

36 



4 

— 

4 

1 J 31oz.  1 g 

40 



2 



1 

3 

37 



3 

1 

2 

6 

■ “ 1 1 s 

41 



3 

— 

2 

5 

5 4 to  ^ S 

38 

2 





— 

2 

g?  L 40oz.  J ia 

42 

2 

4 

2 

— 

8 

g 1 45oz.  J ^ 

39 



3 

1 

2 

6 

ft 

43 



6 

2 

3 

11 

40 

3 

3 

— 

4 

10 

44 

1 

6 

2 

3 

12 

41 

2 

8 



2 

12 

50 

45 

6 

8 

— 

1 

15 

42 

3 

6 

1 

3 

13 

46 

2 

10 



8 

20 

43 

6 

6 



7 

19 

/"  from  p 

47 

2 

6 



10 

18 

44 

5 , 

4 



13 

22 

j g ; 4ioz.  t ^ 

48 

4 

8 

2 

11 

25 

» ^ from  ..  g 

45 

4 

9 

7 

20 

45  \ CM 

49 

3 

2 

2 

12 

19 

1 / 46oz.  \ § 

46 

2 

9 

2 

12 

25 

a 1 47oz.  ) is 

50 

4 

4 

5 

13 

26 

Ml  r I 

47 

2 

5 

7 

14 

p 

51 

3 

3 

2 

19 

27 

g 1.  53oz.  ) 

48 



2 

2 

2 

6 

52 



5 

4 

6 

15 

s 

49 



1 

2 

7 

10 

53 

4 

2 

4 

10 

20 

50 



2 

1 

4 

7 

^ , from  ^ a, 

54 

3 

2 

1 

5 

11  ' 

51 





2 

4 

6 

55 



— 

2 

4 

6 

52 

1 



. 

— 

1 

56 

— 

— 

1 

6 

7 

. 

53 

— 

1 

— 

— 

1 

^ (_  56oz.  J ^ 

57 

— 

— 

— 

2 

2 

tH 

54 

— 

2 

— 

— 

2 

P 

58 



1 

4 

2 

7 

“ ( from  4 g 

56 



1 

— 

1 

59 



1 

2 

3 

6 

[ S J 54oz.  1 g 

60 

61 

— 

— 

2 

1 

1 

1 

3 

“1  to  f g 
^ *-  65oz.  J 

62 



— 

1 

— 

1 

P 

63 

— 

— 

— 

1 

1 

65 

— 

— 

1 

— 

1 

Tot.  35  + 78+  39+126—278  Tot.  30  + 72 +12+77  =•  191 


According  to  this  table,  the  maximum  weight  of  the  adult  male  brain,  in  a 
series  of  278  cases,  was  65  oz.,  and  the  minimum  weight  34  oz.  In  a series  of 
191  cases,  the  maximum  weight  in  the  adult  female  was  56  oz.,  and  the  minimum 
31  oz.;  the  difference  between  the  extreme  weights  in  the  male  subject  being  no 
less  than  31  oz.,  and  in  the  female  25  oz.  The  weight  of  the  adult  male  brain 
appears,  therefore,  to  be  subject  to  a wider  range  of  variety  than  that  of  the 
female.  By  grouping  the  cases  together  in  the  manner  indicated  by  brackets,  it 
is  found  that  in  a very  large  proportion,  the  weight  of  the  male  brain  ranges  be- 
tween 46  oz.  and  53  oz.,  and  that  of  the  female  brain  between  41  oz;  and  47  oz. 
The  prevailing  weights  of  the  adult  male  and  female  brain  may  therefore  be  said 
to  range  between  those  terms ; and  by  taking  the  mean,  an  average  weight  is 
deduced  of  49^  oz.  for  the  male,  and  of  44  oz.  for  the  female  brain, — results 
which  correspond  closely  with  the  statements  generally  received. 

Although  many  female  brains  exceed  in  weight  particular  male  brains,  the 
general  fact  is  sufficiently  shown,  that  the  adult  male  encephalon  is  heavier  than 
that  of  the  female, — the  average  difference  being  from  5 to  6 oz.  This  general 


CEREBRO-SPINAL  AXIS. 


187 


superiority  in  absolute  weight  of  the  male  over  the  female  brain,  is  shown  by 
Table  II.  to  exist  at  every  period  of  life.  In  new-born  infants  the  brain  was 
found  by  Tiedemann  to  weigh  lAi  oz.  to  15|  oz.  in  the  male,  and  10  oz.  to  13J 
oz.  in  the  female.* * * § 

Anatomists  have  differed  considerably  in  their  statements  as  to  the  period  at 
which  the  brain  attains  its  full  size,  and  also  as  to  the  effect  of  old  age  in  diminish- 
ing the  weight  of  this  organ.  Scemmerring  concluded  that  the  brain  reached  its 
full  size  as  early  as  the  third  year;  the  Wenzels  and  Sir  W.  Hamilton  fixed  the 
period  about  the  seventh,  and  Tiedemann  between  the  seventh  and  eighth. 
GaU  and  Spurzheim  were  of  opinion  that  the  brain  continued  to  grow  until  the 
fortieth  year.  The  tables  of  Dr.  Sims  show  a gradual  increase  in  the  weight 
of  the  brain  up  to  the  twentieth  year,  and  a further  irregular  increase, 
until  the  maximum  is  reached  between  forty  and  fifty  years,  after  which  there 
is  a decrease.  From  the  following  Table  (II.),  founded  on  the  observations  of 
Sims,  Tiedemann,  and  Reid,  it  appears  that  in  general  the  weight  of  the  brain 
increases  rapidly  up  to  the  seventh  year,  then  more  slowly  to  between  sixteen 
and  twenty,  and  again  more  slowly  to  between  thirty-one  and  forty,  at  which 
time  it  reaches  its  maximum  point.  Beyond  that  period,  there  appears  a slow 
but  progressive  diminution  in  weight  of  about  1 oz.  during  each  subsequent  de- 
cennial period;  thus  confirming  the  opinion,  that  the  brain  diminishes  in  ad- 
vanced life.  It  will  also  be  seen  from  the  table  that  the  general  results  are  the 
same  in  both  sqxes. 

All  other  circumstances  being  alike,  the  size  of  the  brain  appears  to  bear  a 
general  relation  to  the  mental  power  of  the  individual, — although  instances  occur 
in  which  this  rule  is  not  applicable.  The  brain  of  Cuvier  weighed  upwards  of  64 
oz.,t  and  that  of  the  late  Dr.  Abercrombie  about  63  oz.  avoirdupois. $ On  the 
other  hand,  the  brain  in  idiots  is  remarkably  small.  In  three  idiots,  whose  ages 
were  sixteen,  forty,  and  fifty  years,  Tiedemann  found  the  weight  of  their  respec- 
tive brains  to  be  19|  oz.,  25|  oz.,  and  22i  oz  ; and  Dr.  Sims  records  the  case  of  a 
female  idiot  twelve  years  old,  whose  brain  weighed  27  oz. 

The  weight  of  the  human  brain  being  taken  at  about  3 lbs.  (48  oz.),  it  is  found 
to  be  absolutely  heavier  than  the  brain  of  all  the  lower  animals  except  the  ele- 
phant and  whale.  In  the  elephant,  the  brain,  according  to  Perrault,  Moulins, 
and  Sir  A.  Cooper,  weighs  between  8 and  10  lbs.;  whilst  that  of  the  whale  was 
found  by  Rudolphi,  in  a specimen  75  feet  long,  to  weigh  upwards  of  5 lbs.§ 

The  relative  weight  of  the  e^icephalon  to  the  body  is  liable  to  great  variation;  never- 
theless, the  facts  to  be  gathered  from  the  tables  of  Clendinning,  Tiedemann,  and 
Reid.,  furnish  this  interesting  general  result ; — In  a series  of  81  males,  the  ave- 
rage proportion  between  the  weight  of  the  brain  and  that  of  the  body,  at  the 
ages  of  twenty  years  and  upwards,  was  found  to  be  as  1 to  36‘5;  and  in  a series 
of  82  females,  to  be  as  1 to  36-46.  In  these  cases,  the  deaths  were  the  result  of 
more  or  less  prolonged  disease ; but  in  6 previously  healthy  males,  who  died 
suddenly  from  disease  or  accident,  the  average  proportion  was  1 to  40-8. 

The  proportionate  weight  of  the  brain  and  body  is  greater  at  birth  than  at  any 
other  period  of  life,  being,  according  to  Tiedemann,  about  1 to  5-85  in  the  male, 
and  about  1 to  6-5  in  the  female.  From  the  tables  already  referred  to,  it  further 
appears  that  the  proportion  diminishes  gradually  up  to  the  tenth  year,  being  then 
about  1 to  14.  From  the  tenth  to  the  twentieth  year,  the  relative  increase  of  the 
hody  is  most  striking,  the  ratio  of  the  two  being  at  the  end  of  that  period  about 
1 to  30.  After  the  twentieth  year,  the  generrd  average  of  1 to  36'5  prevails,  with 
a further  trifling  decrease  m advanced  life. 

* This  fact  is  not  without  interest  in  practical  midwifery,  for  it  has  been  shown  that  by 
far  the  larger  number  of  difficult  labours  occur  in  the  birth  of  male  children.  Professor 
Simpson — London  and  Edinburgh  Monthly  Journal  of  Medical  Science,  1845. 

■t  Emille  Rousseau — Maladie  et  autopsie  de  M.  G.  Cuvier.  Lancette  Fran9aise.  Mas 
26,  18.32.  The  precise  weight  given  by  M.  Rousseau  is  3 livres,  11  ounces,  4^  gros  (old 
French  weight).  This  being  reduced  to  kilogrammes  and  thence  converted  into  oz.  avoir- 
dupois, gives  64  oz.  and  nearly  one-third. 

t Cormack’s  Journal,  December,  1844.  Dupuytren’s  brain  is  stated  by  Tiedemann  (op. 
cit.  p.  9,)  to  have  weighed  58  oz.  apothecary’s  wt.  = 63J  oz.  avoirdupois.  But  in  the  Re- 
port  of  the  Autopsy  published  in  the  Lancette  Frangaise,  Feb.  1835,  the  weight  is  given 
as  2 livres  14  ounces  (old  French  wt.)  = only  to  50  oz.  Avoirdupois. 

§ In  Tiedemann,  op.  cit.  p.  15. 


188 


CEREBRO-SPINAL  AXIS. 


TABLE  II. 


CEREBRO-SPINAL  AXIS. 


189 


Viewed  in  relation  to  the  weight  of  his  body,  the  brain  of  man  may  be  stated 
generally  to  be  heavier  than  the  brains  of  the  lower  animals ; but  there  are  some 
exceptions  to  the  rule,  as  in  the  case  of  certain  species  of  small  birds,  in  the 
smaller  apes,  in  monkeys,  and  in  some  small  rodent  animals. 

In  some  of  the  examples  in  the  following  table,*  the  brain  is  heavier,  and  in 
others  lighter  relatively  to  the  body  than  it  is  in  man. 


Blue-headed  Tit 

1 

to 

12 

Porpoise 

1 

to 

93 

Canary 

1 

to 

14 

Rabbit 

1 

to 

140 

Goldfinch 

1 

to 

24 

Cat  . 

1 

to 

156 

Linnet 

1 

to 

24 

Dog 

1 

to 

305 

Monkey  (small) 

1 

to 

22 

Horse 

1 

to 

400 

Field-mouse 

1 

to 

31 

Elephant 

1 

to 

500 

Gibbon  . 

1 

to 

48 

Sheep 

1 

to 

350 

Rat 

1 

to 

76 

Ox 

1 

to 

860t 

M.  Leuretf  has  found,  from  extensive  observation,  that  the  proportionate 
weight  of  the  brain  to  the  body,  in  the  four  classes  of  vertebrate  animals,  may  be 
represented  by  the  following  numbers : 

In  Fishes,  as  1 to  5668  In  Birds,  1 to  212 

Reptiles,  1 to  1321  Mammalia,  1 to  186 

WEIGHTS  OF  THE  SEVERAL  PARTS  OF  THE  ENCEPHALON. 


As  the  result  of  observations  made  in  reference  to  this  subject,  on  the  brains  of 
53  males  and  34  females,  between  the  ages  of  twenty-five  and  fifty-five,  Dr.  J, 
Reid  has  given  the  following  table : — 


Average  weight  of  cerebrum 
“ cerebellum 

“ pons  and  medulla 

oblongata 

“ entire  encephalon 


Males;  Females.  Difference. 


OZ. 

drs. 

OZ. 

drs. 

OZ. 

drs. 

43 

15| 

38 

12 

5 

3| 

5 

4 

4 

12i 

0 

7| 

15| 

1 

Oi 

0 

50 

3i 

44 

8i 

5 

11 

From  this  it  appears  that  the  proportionate  weight  of  the  cerebellum  to  that  of 
the  cerebrum,  is,  in  the  male,  as  1 to  8|,  and  in  the  female  as  1 to  8I-. 

In  the  new-born  infant  the  ratio  is  strikingly  different  to  what  it  is  in  the  adult, 
being,  according  to  Chaussier,  from  1 to  13  to  1 to  26;  by  CruveiUiier  it  was 
found  to  be  1 to  20. 

In  most  mammalia,  the  cerebellum  is  found  to  be  heavier  in  proportion  to  the 
cerebrum,  than  it  is  in  the  human  subject;  in  other  words,  the  cerebrum  is 
larger  in  proportion  to  the  cerebellum  in  man. 

Soemmerring^  pointed  out  the  fact  that  the  brain  is  larger  in  proportion  to  the 
nerves  connected  with  it  in  man  than  in  the  lower  animals.  With  the  view  of 
showing  the  size  of  the  brain  in  proportion  to  the  rest  of  the  nervous  system  in 
different  cases,  a comparison  has  been  made  of  the  width  of  the  cerebrum  with 
that  of  the  medulla  oblongata.  From  this  it  appears,  that  the  proportionate  dia- 
meter of  the  brain  to  that  of  the  medulla  oblongata  is  greater  in  man  than  in  any 
animal,  except  the  dolphin,  in  which  creature  it  must  be  remembered  that  the 
cerebral  lobes  exhibit  a disproportionate  lateral  development.  The  width  of  the 
cerebrum  in  man,  as  compared  with  that  of  the  medulla  oblongata  at  its  base  or 
broadest  part,  is  about  7 to  1. 


* Selected  from  Cuvier’s  Le5ons,  &c.,  2d  edition,  par  F.  G.  Cuvier  & Laurillard.  1845. 
Paris. 

t We  are  indebted  to  Professor  Owen  for  the  following  information  concerning  the  rela- 
tive  weight  of  the  brain  and  body  in  the  Chimpanzee  (Simia  Troglodytes). 

Weight  of  brain,  in  a half-grown  male  . . 9|  oz. 

Weight  of  body,  in  a nearly  adult  female,  61  lbs.  = 976  oz. 

Proportion  between  the  two  weights  1 to  100. 
t Anat.  Comp,  du  Syst.  Nerv.,  &c.  Paris,  1839.  Tom.  i.,  p.  423. 

§ De  basi  encephali,  Goettingae.  1778. 


190 


THE  SPINAL  CORD. 


In  the  ourang  it  is 

6 to 

1 

In  certain  monkeys 

. 5 and  4 to 

1 

In  the  dog 

. 11  to 

6 

In  the  cat  . 

11  to 

4 

In  the  rabbit  . 

8 to 

3 

In  the  ox  . 

13  to 

5 

In  the  horse 

. 21  to 

8 

In  the  falcon 

34  to 

13 

In  the  sparrow 

. 18  to 

7 

In  the  dolphin 

13  to 

WEIGHT  OF  THE 

SPINAL  CORE 

1, 

Divested  of  its  membranes  and  nerves,  the  spinal  cord  in  the  human  subject 
weighs  from  1 oz.  to  oz.,  and  therefore  its  proportion  to  the  encephalon  is 
abouf-l  to  33.  Meckel  gives  it  as  1 to  40. 

The  disproportion  between  the  brain  and  the  spinal  cord, becomes  less  and 
less  in  descending  the  scale  of  the  vertebrata,  until  at  length,  in  the  cold-blooded 
animals,  the  spinal  cord  becomes  heavier  than  the  brain.  Thus,  in  the  mouse, 
the  weight  of  the  brain,  in  proportion  to  that  of  the  spinal  cord,  is  as  4 to  1 ; in 
the  pigeon,  as  3§  to  1 ; in  the  newt,  only  as  | to  1 ; and  in  the  lamprey,  as 
to  1. 

In  comparison  with  the  size  of  the  body,  the  spinal  cord  in  man  may  be  stated  in 
general  terms  to  be  much  smaller  than  it  is  in  animals.  In  regard  to  the  cold- 
blooded animals,  to  birds,  and  to  smaU  mammalia,  this  has  been  actually  de- 
monstrated, but  not  in  reference  to  the  larger  mammalia. 

THE  SPINAL  CORD. 

The  spinal  cord,  or  spinal  marrow  (medulla  spinalis),  is  that  part  of 
the  cerebro-spinal  axis  which  is  situated  within  the  vertebral  canal.  It 
extends  from  the  margin  of  the  foramen  magnum  of  the  occipital  bone, 
to  about  the  lower  part  of  the  body  of  the  first  lumbar  vertebra.  It 
forms  the  continuation  of  the  medulla  oblongata  above,  and  ends  be- 
low in  a slender  filament,  which  is  prolonged  to  the  termination  of  the 
sacral  canal. 

The  spinal  cord  does  not  occupy,  either  by  its  length  or  thickness, 
the  entire  space  within  that  canal.  On  the  contrary,  invested  closely 
by  a proper  membrane  (the  pia  mater),  the  cord  is  enclosed  within  a 
sheath,  both  longer  and  larger  than  itself,  which  is  formed  by  the  dura 
mater,  and  which  is  itself  separated  from  the  walls  of  the  canal  by 
numerous  vascular  plexuses,  and  much  loose  cellular  tissue.  The  in- 
terval between  the  investing  membrane  and  the  sheath  of  the  cord,  is 
lined  by  a serous  membrane  (the  arachnoid),  and  is  filled  by  a fluid 
called  the  cerebro-spinal  fluid.  Within  this  space  the  cord  is  sus- 
pended or  supported  by  proper  ligaments,  which  serve  to  fix  it  at  dif- 
ferent points  to  its  sheath.  The  anterior  and  posterior  roots  of  the 
several  pairs  of  spinal  nerves  pass  across  the  space  from  the  surface 
of  the  cord,  towards  the  corresponding  intervertebral  foramina.  Since 
the  cord  terminates  at  the  upper  part  of  the  lumbar  region,  it  occupies 
only  the  two  upper  thirds  of  the  spinal  canal,  and  the  elongated  roots 
of  the  lumbar  and  sacral  nerves,  which  descend  nearly  vertically  from 
the  cord  to  reach  the  lumbar  intervertebral  and  the  sacral  foramina, 
form  a lash  of  nervous  cords  named  the  cauda  equina,  which  occu- 
pies the  remaining  and  lower  third  of  the  spinal  canal. 

* Cuvier’s  Legons  ; ut  supra. 


THE  SPINAL  CORD. 


191 


Although  the  cord  usually  ends  near  the  lower  border  of  the  body 
of  the  first  lumbar  vertebra,  it  sometimes  terminates  a little  above  or 
below  that  point,  as  opposite  to  the  last  dorsal  or  to  the  second  lumbar 
vertebra.  The  position  of  the  lower  end  of  the  cord  also  varies 
according  to  the  state  of  curvature  of  the  vertebral  column,  in  the 
flexion  forwards  of  which,  as  in  the  stooping  posture,  the  end  of  the 
cord  is  slightly  raised. — In  the  fetus,  at  an  early  period,  the  length  of 
the  cord  corresponds  with  that  of  the  vertebral  canal ; but  after  the 
third  month,  the  canal  and  the  roots  of  the  lumbar  and  sacral  nerves 
begin  to  grow  more  rapidly  in  proportion,  so  that  at  birth  the  lower 
end  of  the  cord  reaches  .only  to  the  third  lumbar  vertebra. 

The  length  of  the  spinal  cord  is  from  fifteen  to  eighteen  inches  ; and 
it  varies  in  diameter  in  different  situations.  Its  general  form  is  cylin- 
drical, but  it  is  somewhat  flattened  before  and  behind.  It  is  not  of 
uniform  size  or  shape  throughout,  but  presents  two  enlargements — an 
upper,  or  cervical,  and  a lower,  or  lumbar.  The  cervical  enlarge- 
ment is  of  greater  size  and  extent  than  the  lower.  It  reaches  from  the 
third  cervical  to  the  first  dorsal  vertebra  ; its  greatest  diameter  is  from 
side  to  side.  The  lower  or  lumbar  enlargement  is  situated  about  oppor 
site  the  last  dorsal  vertebra  ; its  greatest  diameter  is  from  before  back- 
wards, and  by  Foville*  it  is  said  to  be  chiefly  due  to  an  increase  in 
bulk  of  the  anterior  region  of  the  cord. — Below  this  enlargement,  the 
cord  tapers  into  a conical  point.  Sometimes  it  forms  one  or  two  bulbs 
or  swellings  towards  its  lower  end.  The  cervical  and  lumbar  en- 
largements have  an  evident  relation  to  the  size  of  the  nerves  which 
supply  the  upper  and  lower  limbs,  and  which  are  connected  with 
those  regions  of  the  cord, — in  accordance  with  the  general  fact  ob- 
served in  the  animal  kingdom,  that  near  the  origin  of  large  nerves,  the 
nervous  substance  is  accumulated  in  larger  proportion.  On  its  com- 
mencement in  the  embryo,  the  spinal  cord  is  destitute  of  these  en- 
largements, which,  in  their  first  appearance  and  subsequent  progress, 
correspond  with  the  growth  of  the  limbs. 

The  long  free  and  slender  filament  in  which  the  cord  terminates, 
descends  in  the  middle  line  amongst  the  nerves  composing  the  cauda 
equina,  and,  becoming  blended  with  the  lower  end  of  the  sheath  oppo- 
site to  the  first  or  second  sacral  vertebra,  passes  on  to  be  fixed  to  the 
lower  end  of  the  sacral  canal,  or  to  the  ba.se  of  the  coccyx.  It  is 
named  the  central  ligament  of  the  spinal  cord ; it  is  of  a fibrous  struc- 
ture, and  contains  no  nervous  substance,  except  for  a short  distance 
at  its  upper  end ; it  is,  therefore,  not  a nerve,  although  it  was  at  one 
time  so  considered,  and  was  named  nervus  impar.  It  appears  to  be  a 
prolongation  of  the  pia  mater  or  innermost  membrane,  which,  being 
attached  at  its  lower  end  to  the  dura  mater  and  vertebral  panal  keeps 
pace  with  the  latter  in  its  growth,  whilst  the  cord  relatively  shortens. 
It  consists  of  fibrous  tissue  with  a few  fine  elastic  filaments  intermixed; 
and  it  must  assist  in  supporting  the  cord,  and  in  maintaining  its  posi- 
tion during  the  movements  of  the  trunk.  A small  vein  has  been 
sometimes  seen  upon  it. 

* Traite  compl.  de  I’Anat,  &c.  du  Syst.  Nerv.  Cerebro-Spinal.  Paris,  1844.  Part  I., 
p.  138. 


192 


THE  SPINAL  CORD. 


When  removed  from  the  vertebral  canal,  and  divested  of  its  mem- 
branes, the  spinal  cord  is  seen  to  be  marked  by  longitudinal  fissures. 
Of  these,  two  run  along  the  middle  line,  one  in  front  and  the  other 
behind,  and  are  named  the  anterior  and  posterior  median  fissures,  fig. 
326,  a and  p.  By  means  of  these,  which  penetrate  only  a certain 
distance  into  its  substance,  the  cord  is  divided  into  two  lateral  and 
symmetrical  halves,  which,  however,  are  connected  in  their  whole  length 
by  a cross  portion  of  nervous  substance  called  the  commissure. 

The  anterior  median  fissure,  a a,  is  more  distinct  than  the  posterior. 


Fig.  326. 


Plans  in  outline,  showing 
the  front  a,  and  the  sides,  B, 
of  the  spinal  cord  with  the  fis- 
sures upon  it;  also  sections  of 
the  gray  and  white  matter, 
and  the  roots  of  the  spinal 
nerves,  a,  a.  Anterior,  p,  p. 
Posterior  fissure,  b.  Posterior, 
and  c.  Anterior  horn  of  gray 
matter,  e.  Gray  commissure. 
aec.  Anterior  white  column. 
ceb.  Lateral  columns,  aeb, 
antero-lateral  column,  hep. 
Posterior  columns,  r,  Anterior, 
and  s.  Posterior  roots  of  a spinal 


and  penetrates  about  one-third  of  the  thickness 
of  the  cord,  but  its  depth  increases  towards  the 
lower  end.  It  contains  a fold  or  lamelliform 
process  of  the  pia  mater,  and  also  many  blood- 
vessels, which  are  thus  conducted  to  the  centre 
of  the  cord.  At  the  bottom  of  this  fissure  is 
seen  the  connecting  portion  of  white  substance 
named  the  anterior  white  commissure. 

The  posterior  median  fissure,  p p,  is  less 
marked  in  the  greater  part  of  its  extent  than 
the  anterior,  but  becomes  more  evident  towards 
the  upper  part  of  the  cord.  Numerous  blood- 
vessels, accompanied  by  slender  filamentous 
processes  derived  from  the  inner  membrane, 
pass  into  this  fissure.  Lastly,  the  bottom  of 
the  fissure  is  separated  from  the  central  gray 
matter  of  the  cord  only  by  a very  thin  layer 
of  white  substance,  which  has  been  named  the 
posterior  white  commissure ; but  some  main- 
tain that  the  fissure  actually  reaches  the  gray 
matter. 

Besides  these  two  median  fissures,  two  late- 
ral furrows  or  fissures  have  been  described  on 
each  side  of  the  cord,  corresponding  with  the 
lines  of  attachment  of  the  spinal  nerves.  The 
anterior  and  posterior  roots  of  these  nerves,  as 
will  be  hereafter  specially  described,  are  at- 
tached to  the  cord  in  four  rows,  of  which  two 


are  seen  in  front,  fig.  326,  r,  at  a little  distance 
on  either  side  of  the  anterior  median  fissure,  and  two  behind,  s,  near 
the  posterior  median  fissure.  Now,  along  the  line  of  attachment  of 
the  posterior  roots,  there  is  in  each  half  of  the  cord  a fissure  leading 
down  to  the  gray  matter,  which  there  comes  to  the  surface.  This  is 
the  posterior,  lateral  fissure,  h,  by  which  the  corresponding  half  of  the 
cord  is  divided  into  an  anterior  and  a posterior  column. 

By  some  anatomists,  an  anterior  lateral  fissure  has  been  described 
as  existing  along  the  line  of  attachment  of  the  anterior  roots,  b,  c c' ; 
but,  in  reality,  there  is  no  fissure  to  be  seen  on  the  surface  at  this  part, 
although  the  white  substance  of  the  cord  is  divided  by  a prolongation 
of  the  gray  matter,  a,  c,  from  within,  which,  however,  does  not  reach 
the  surface.  Thus,  each  lateral  half  of  the  cord  is  divided  by  the  pos- 


THE  SPINAL  CORD. 


193 


terior  lateral  fissure  into  a posterior,  p e b,  and  an  antero-lateral 
column,  a eb;  and  although  we  cannot  trace  an  anterior  lateral  fissure, 
this  antero-lateral  portion  of  the  cord  may,  for  the  convenience  of 
description,  be  considered  as  subdivided  into  an  anterior  and  a lateral 
column  by  the  internal  gray  matter. 

On  the  posterior  surface  of  the  cord  (throughout  its  ichole,  length, 
according  to  Foville,  but  much  more  evidently  in  the  upper  part,)  there 
are  two  slightly-marked  longitudinal  furrows  situated  one  on  each  side, 
close  to  the  posterior  median  fissure,  and  marking  off,  at  least  in  the 
cervical  region,  a slender  tract,  named  the  posterior  median  column. 
Between  the  roots  of  the  spinal  nerves,  on  each  side,  the  cord  is  con- 
vex, and  sometimes  has  a longitudinal  mark  upon  it,  corresponding 
with  the  line  of  attachment  of  the  ligamentum  denticulatum. 

Foville*  states  that  in  a new-born  child,  there  is  a narrow  accessory  bundle 
of  white  matter,  running  along  the  surface  of  the  lateral  column,  separated  from 
it  by  a streak  of  grayish  substance.  According  to  the  ^ame  authority,  this  narrow 
tract  enlarges  above,  and  may  be  traced  upwards  along  the  side  of  the  medulla 
oblongata  into  the  cerebellum. 

Structure  of  the  spinal  cord. — The  spinal  cord  consists  of  white  and 
gray  nervous  substance.  The  white  matter  is 
situated  externally,  whilst  the  gray  matter  is 
disposed  in  the  interior,  in  a peculiar  mapner, 
to  be  now  described.  On  a transverse  section, 
figs.  326,  327,  it  presents  two  crescent-shaped 
masses  of  similar  form,  placed  one  in  each 
lateral  half  of  the  cord  with  their  convexities 
towards  one  another,  and  joined  across  the 
middle  by  a transverse  portion  of  gray  matter. 

Each  of  these  gray  crescents  has  an  anterior 
and  a posterior  cornu  or  horn.  Of  these,  the 
posterior  is  long  and  narrow,  and  reaches  the 
surface  at  the  posterior  lateral  fissure.  The 
anterior  horn  is  shorter  and  thicker  than  the 
posterior ; it  extends  towards  the  line  of  attach- 
ment of  the  anterior  roots  of  the  nerves,  but  it 
does  not  reach  the  surface  of  the  cord.  The 
transverse  median  portion  o{gray  matter  which 
connects  the  two  crescents  is  named  the  gray 
commissure  of  the  cord,  e.  In  front  of  it,  there 
is^  a tolerably  thick  layer  of  white  substance, 
separating  it  from  the  bottom  of  the  anterior 
median  fissure,  a ; this  is  named  the  anterior 
white  commissure.  In  like  manner  there  is  an- 
other white  layer  behind  the  gray  matter,  named 
the  posterior  white  commissure,  but  this  is  very 

Fig.  327.  Transverse  section  of  the  spinal  cord : — a.  Immedi- 
ately below  the  decussation  of  the  pyramids,  b.  At  middle  of  cer- 
vical bulb.  c.  Midway  between  cervical  and  lumbar  bulbs,  d. 

Lumbar  bulb.  e.  An  inch  lower,  f.  Very  near  the  lower  end. 
a.  Anterior  surface,  p.  Posterior  surface.  The  points  of  emerg- 
ence of  the  anterior  and  posterior  roots  of  the  nerves  are  also  seen. 

— Todd  and  Bowman.] 


[Fig.  327. 
P 


a 


VOL.  II. 


* Op.  cit.  p.  285. 
17 


194 


THE  SPINAL  CORD. 


thin  and  indistinct,  so  that  its  existence  has  been  denied  by  anatomists, 
of  good  authority. 

At  its  junction  with  the  white  substance,  the  gray  matter  presents  a 
somewhat  jagged  or  indented  outline,  especially  in  the  anterior  horn 
of  each  crescent. 

At  the  tip  of  the  posterior  horn,  which  is  somewhat  enlarged,  the 
gray  matter  has  a peculiar  semi-transparent  aspect,  whence  ^it  was 
named  by  Rolando,  substantia  cinerea  gelatinosa. 

The  white  substance  forms  by  far  the  larger  portion  (it  is  said 
nearly  seven-eighths)  of  the  cord.  Owing  to  the  peculiar  arrange- 
ment of  the  gray  matter,  the  white  substance  in  each  semi-cylin- 
drical half  of  the  cord  is  divided  into  two  principal  columns,  which 
have  been  already  noticed  in  describing  its  surface ; viz.,  a posterior 
and  an  antero-lateral  column.  The  posterior  column,  fig.  326,  p e b, 
is  situated  between  the  posterior  median  fissure  and  the  posterior 
lateral  fissure  with  the  corresponding  cornu  of  the  gray  matter : it  is 
wedge-shaped,  the  point  of  the  wedge  being  directed  forwards  towards 
the  centre.  The  remaining  portion  of  white  substance  constitutes  the 
antero-lateral  column  a e b,  which  is  bounded  behind  by  the  posterior 
cornu  of  gray  matter  b,  and  on  the  inner  side  by  the  anterior  median 
fissure  a.  It  is  partially  subdivided  by  the  anterior  gray  cornu  c,  into 
a lateral,  c e b,  and  an  anterior  column,  a e c,  the  latter  being  joined 
to  the  corresponding  column  of  the  other  half  of  the  cord  by  means  of 
the  white  commissure. 

According  to  this  view  there  are  three  principal  columns  in  each 
half  of  the  cord,  viz.,  an  anterior,  a lateral,  and  a posterior  column, 
in  addition  to  the  slender  tract  adjoining  the  posterior  median  fissure 
already  described,  which  is  generally  reckoned  as  part  of  the  posterior 
column. 

The  white  substance  of  the  cord  has  been  described  as  if  disposed 
in  thin  wedge-shaped  and  longitudinal  laminae,  placed  in  a radiating 
manner,  with  their  edges  in  contact  with  the  gray  matter.  Such  a 
regular  arrangement  of  lamellae  does  not  exist,  but  the  white  substance 
is  collected  into  compressed  longitudinal  bundles,  between  which  small 
blood-vessels  run  transversely  into  the  substance  of  the  cord,  sup- 
ported for  a certain  distance  by  delicate  processes  of  membrane 
derived  from  the  pia  mater. 

There  is  an  appearance  of  transverse  decussating  bundles  in  the 
anterior  commissure,  but  this  is  to  be  attributed  to  the  frequent  inter- 
ruption of  the  white  substance  by  foramina  for  the  transmission  of 
small  blood-vessels. 

The  arrangement  of  the  white  and  gray  substances,  though  agree- 
ing generally  with  the  description  just  given,  is  somewhat  modified  at 
different  parts  of  the  cord,  as  may  be  seen  in  sections  made  at  diffe- 
rent heights.  Thus,  the  horns  of  the  gray  crescents  are  long  and 
slender  in  the  cervical  portion,  fig.  327,  a,  b,  short  and  more  slender 
in  the  dorsal,  c,  and  short  but  much  wider  in  the  lumbar  region,  d,  e; 
so  that  the  gray  matter  appears,  in  a series  of  sections,  to  be,  rela- 
tively to  the  white,  more  abundant  in  the  lumbar  region  of  the  cord, 
E,  less  so  in  the  cervical  region,  a,  b,  and  least  so  in  the  dorsal,  c. 


THE  ENCEPHALON. 


195 


The  quantity  of  white  matter  is  greatest  in  the  neck.  Towards  the 
lower  end  of  the  cord  f,  the  double  crescentic  appearance  gradually 
ceases,  and  the  gray  matter  is  collected  into  a Central  mass,  which  is 
indented  at  the  sides.  At  its  extreme  point,  according  to  Remak  and 
Valentin,  it  consists  of  gray  matter  only. 

In  fishes,  reptiles,  and  birds,  during  the  whole  period  of  life,  a canal 
exists  along  the  centre  of  the  spinal  cord.  It  is  found  also  in  the  foetus 
of  mammiferous  animals,  and  even  in  the  young  of  that  class.  In  the 
human  foetus,  as  shown  by  Tiedemann,  there  also  exists,  until  after  the 
sixth  month,  a central  canal  formed  by  the  closing  in  of  an  open 
groove  previously  existing.  In  the  adult  human  subject,  the  upper 
portion  of  this  canal  can  be  traced  from  the  point  of  the  calamus 
scriptorius  in  the  floor  of  the  fourth  ventricle,  for' about  half  an  inch 
or  more  down  the  centre  of  the  cord,  where  it  ends  in  a cul-de-sac. 
Much  controversy,  however,  has  prevailed  in  regard  to  the  extent  to 
which  this  canal  exists  in  the  adulfland  many  writers  have  maintained 
that  it  is  to  be  found  through  the  whole  length  of  the  cord,  situated 
between  the  gray  and  white  cpm'missures. 

The  attention  of  anatomists  has  recently  been  directed  to  this  point 
by  the  microscopic  observations  of  Drs.  Stilling  and  Wallach,*  who 
maintain  that  the  canal  may  be  traced  in  the  adult  low  down  in  the 
cord,  appearing  on  a section  as  a small  round  foramen  in  the  centre 
of  the  gray  matter.  We  must  confess  that,  on  careful  examination, 
we  have  only  now'  and  then  been  able  to  discover  an  aperture,  which 
has  much  the  appearance  of  a divided  blood-vessel. 

The  minute  or  microscopic  structure  of  the  cord,  including  the 
arrangement  of  the  roots  of  the  nerves  within  it,  will  be  considered 
afterwards. 

THE  ENCEPHALON. 

We  have  now  to  describe  the  four  principal  parts  into  which  the 
encephalon  is  divided,  viz.,  the  cerebrum,  the  cerebellum,  the  pons 
Varolii,  and  the  medulla  oblongata.  But  their  general  position  within 
the  skull,  and  their  relations  to  each  other,  require  first  to  be  under- 
stood. 

The  cerebrum,  fig.  328,  a,  which  constitutes  the  highest  and  by  far 
the  largest  part  of  the  human  encephalon,  occupies  the  upper  and 
larger  portion  of  the  cranial  cavity.  A line  drawn  from  a little  above 
the  orbit  to  the  auditory  meatus,  met  by  another  from  the  occipital 
protuberance  to  the  same  point  will  nearly  indicate  on  the  living  head, 
the  inferior  limit  of  the  cerebrum.  In  front,  it  rests  in  the  anterior 
fossa  of  the  base  of  the  skull ; behind  this,  in  the  middle  fossa ; and 
still  further  back  it  overlies  the  cerebellum,  beyond  which  it  projects 
posteriorly,  resting  on  the  tentorium,  a horizontal  partition  formed  by 
the  dura  mater  between  the  cerebrum  and  the  cerebellum.  In  all  this 
extent,  a.s  well  as  above  and  at  the  sides,  the  cerebrum  is  free  and 
unattached,  but  from  the  middle  of  its  under  surface  there  proceeds  a 
comparatively  narrow  and  constricted  portion,  part  of  which,  a,  form- 

• Uber  die  Textur  des  Rilckenraarks.  Leipzic,  1842. 


196 


ENCEPHALON. 


ing  the  crura  cerebri  or  peduncles  of  the  brain,  descends  into  tbe  pons 
Varolii  below,  and  through  it,  is  continued  into  the  medulla  oblongata; 
whilst  another  part,  passes  down  to  join  the  cerebellum. 


A plan  in  outline,  showing,  in  a lateral  view,  the  parts  of  the  encephalon  separated  somewhat 
from  each  other,  a.  Cerebrum.  f,g,  h.  Its  anterior,  middle,  and  posterior  lobes,  e.  Fissure  of 
Sylvius.  B.  Cerebellum,  c.  Pons  Varolii.  D.  Medulla  oblongata,  a.  Peduncles  of  cerebrum. 
6.  Superior;  c.  Middle  ; and  d,  Inferior  peduncles  of  cerebellum.  The  parts  niarked  a,  b,  c,  c, 
form  the  isthmus  encephali. 


The  cerebellum,  b,  is  placed  beneath  the  hinder  part  of  the  cerebrum, 
by  which  it  is  completely  overlapped,  the  lentorium  separating  one 
from  the  other.  It  is  lodged  in  the  inferior  occipital  fossm,  and  is  at- 
tached to  the  rest  of  the  encephalon,  at  its  fore  part,  by  means  of 
connecting  portions  named  crura : of  these,  two,  b,  ascend  to  the 
cerebrum,  two,  d,  pass  downwards  to  the  medulla  oblongata,  d,  and 
two,  c,  horizontally  forwards,  so  as  to  embrace  the  peduncles  of  the 
brain,  in  front  of  which  they  unite  to  form  the  transverse  eminence  of 
the  fons  Varolii. 

The  jpons,  c,  itself  rests  upon  the  upper  part  of  the  basilar  process, 
in  front ; it  receives  the  cerebral  peduncles  above,  and  the  middle 
crura  of  the  cerebellum  behind  and  at  the  sides;  whilst  the  medulla 
oblongata  is  connected  with  it  below. 

Lastly,  the  medulla  oblongata,  d,  descending  obliquely  backw'ards 
from  the  lower  border  of  the  pons,  is  placed  beneath  the  middle  of 
the  cerebellum,  and  rests  on  tbe  basilar  groove,  until  it  reaches  the 
foramen  magnum,  where  it  is  continuous  with  the  spinal  cord,  t.  ' 

Situated  in  the  interior  of  the  brain,  surrounded  by  nervous  substance 
and  lined  by  a delicate  membrane,  are  certain  serous  cavities,  called 
ventricles.  These,  which  are  five  in  number,  will  be  described  with 
the  parts  of  the  encephalon  in  which  they  occur. 

We  shall  now  proceed  to  describe  those  parts  in  the  following 


Fig.  328. 


t 


MEDULLA  OBLONGATA. 


197 


order : the  medulla  oblongata,  the  pons  Varolii,  the  cerebrum,  and  the 
cerebellum. 

THE  MEDULLA  OBLONGATA. 

The  medulla  oblongata,  fig.  331,  v,  is  that  part  of  the  encephalon 
which  is  immediately  connected  with  the  upper  end  of  the  spinal  cord. 
It  is  bounded  above  by  the  lower  border  of  the  pons  Varolii,  whilst  it 
is  continuous  below  with  the  spinal  cord,  opposite  the  foramen  mag- 
num. By  some,  its  inferior  limit  is,  with  reason,  fixed  rather  lower 
down,  on  a level  with  the  upper  border  of  the  atlas,  at  a point  which 
corresponds  with  the  lower  extremity  of  the  anterior  pyramids,  to  be 
presently  described.* 

The  medulla  oblongata  inclines  obliquely  downwards  and  back- 
wards, fig.  332,  towards  the  foramen  magnum.  Its  anterior  surface 
rests  in  the  basilar  groove,  whilst  its  posterior  surface  is  received  into 
the  fossa,  named  the  vallecula,  between  the  hemispheres  of  the  cere- 
bellum, and  there  forms  the  floor  of  the  fourth  ventricle.  To  its  sides, 
several  large  nerves  are  attached,  fig.  331. 

It  is  of  a pyramidal  form,  fig.  329,  having  its  broad  extremity  turned 
upwards,  from  which  it  tapers  to  its  point  of  connexion  wfith  the 
spinal  cord:  it  is  expanded  laterally  at  its  upper  part.  Its  length  from 
the  pons  to  the  lower  extremity  of  the  pyramids  is  about  an  inch  and 
a quarter;  its  greatest  breadth  is  about  three  quarters  of  an  inch;  and 
its  thickness,  from  before  backwards,  about  half  an  inch. 

The  pia  mater  having  been  removed,  the  medulla  oblongata  is  seen 
to  be  marked  longitudinally  by  an  anterior  and  a posterior  fissure, 
which  are  continuous  with  those  of  the  spinal  cord.  Of  these,  the 
anterior,  between  a a,  terminates  immediately  below  the  pons  p,  in  a 
cul-de-sac,  called  the  foramen  ccEcum,  by  Vicq-d’Azyr.  It  is  pene- 
trated by  a fold  of  the  pia  mater. 

The  •posterior  fissure,  fig.  330,  is  deep  but  narrow ; it  is  continued 
upwards  into  the  floor  of  the  fourth  ventricle,  v v' , where  it  becomes  a 
superficial  furrow  and  is  gradually  lost. 

By  means  of  these  two  fissures,  the  medulla  oblongata  is  partially 
divided  like  the  cord,  into  two  lateral  and  symmetrical  halves.  But 
here  the  resemblance  ceases;  for  on  each  side  of  the  median  line  an 
entirely  new  arrangement  prevails;  the  lateral  fissures  disappear,  and 
the  surface  of  each  half  of  the  medulla  presents  four  eminences  or 
columns,  which,  on  commencing  at  the  anterior  fissure  and  proceeding 
backwards  each  way  to  the  posterior  fissure,  are  met  with  in  the  fol- 
lowing order : the  anterior  pyramids,  the  olivary  bodies,  the  restiform 
bodies,  and  the  posterior  pyramids. 

The  anterior  pyramids,  fig.  329,  a a,  so  called  from  their  position 
and  shape,  are  two  bundles  of  white  substance,  placed  on  either  side 
of  the  anterior  fissure,  which  are  narrower  at  the  lower  end,  and  be- 
come broader  and  more  prominent  as  they  ascend  towards  the  pons 

* The  terra  medulla  oblongata,  as  employed  by  Willis,  by  Vieussens,  and  by  those  who 
directly  followed  them,  included  the  crura  cerebri  and  pons  Varolii,  as  well  as  that  part 
between  the  pons  and  the  foramen  magnum,  to  which,  by  Haller  first,  and  by  most  subse- 
quent writers,  this  terra  has  been  restricted. 

17# 


198 


MEDULLA  OBLONGATA. 


Varolii.  At  their  upper  end  they  are  constricted,  and  thus  enter  the 
substance  of  the  pons,  jp,  through  which  their  fibres  may  be  traced 
into  the  peduncles  of  the  brain.  The  outer  border  of  each  pyramid  is 
marked  off  from  the  olivary  body,  c,  by  a slight  depression.  By  their 
inner  borders  the  pyramids  form  the  sides  of  the  anterior  fissure. 
Over  a space,  commencing  about  eight  or  ten  lines  below  the  pons  and 
extending  to  the  lower  end  of  the  medulla,  a portion  of  each  pyramid, 
arranged  in  several  bundles,  passes  downwards  across  the  fissure  to 
the  opposite  side.  This  decussation  of  the  pyramids,  h,  as  it  is  called. 


Fig.  329.  An  anterior  view  of  the  medulla  oblongata,  a a.  Anterior  pyramids,  b.  Their  de- 
cussation across  the  middle  line,  c c.  The  olivary  bodies,  d d.  Restifbrm  bodies,  e.  Arciforra 
fibres,  f.  Fibres  shown  by  Solly  to  pass  from  the  anterior  column  of  the  cord  to  the  cerebellum. 
g.  Anterior  column,  h.  Lateral  column,  p.  Pons  Varolii.  i.  Its  upper  fibres.  5,  5.  Roots  of 
fifth  nerves. 

Fig.  330.  Posterior  view  of  the  medulla  oblongata,  and  back  of  the  pons  Varolii.  The  pedun- 
cles of  the  cerebellum  are  cut  short,  d d.  Restilbrm  bodies,  (fasciculi  cuneati,)  passing  up  to  be- 
come inferior  peduncles  of  cerebellum.  Posterior  pyramids,  vv/.  Posterior  fissure,  or  cala- 

mus scriptorius,  extending  along  the  floor  of  the  fourth  ventricle,  a a.  Testes,  bb.  Nates,  ff. 
Superior  peduncles  of  cerebellum,  c.  Eminence  connected  with  hypoglossal  nerve,  e.  With 
glosso-pharyngeal  nerve,  i.  With  vagus  nerve,  ti'.  With  spinal  accessory  nerve.  7,  7,  Roots  of 
auditory  nerves. 


is  partial,  for  it  affects  only  the  innermost  fibres,  and  consists  of  from 
three  to  five  intersecting  bundles  from  either  side.  When  traced  from 
below,  it  is  found  that  the  whole,  or  a great  part  of  these  fibres  come 
forwards  from  the  deep  portion  of  the  lateral  columns  of  the  cord  (as 
appears  first  to  have  been  pointed  out  by  Rosenthal),*  and  advance  to 
the  surface,  between  the  diverging  anterior  columns,  gg,  which  are 
thus  thrown  aside. 

The  outer  portion  of  each  pyramid  does  not  decussate  ;f  it  consists 
of  fibres,  derived  from  the  anterior  column  of  the  cord : these  all  as- 

* Ein  Beytrag  zur  Encephalotomie,  1815. 

t The  decussation  of  the  anterior  pyramids  was  noticed  about  the  beginning  of  the  last 
century  by  Misticlielli.  Though  doubte.d  by  Morgagni,  Haller,  Vicq-d’Azyr,  and  many 
others,  it  is  a well-established  fact,  and  has  been  supposed  to  afford  some  explanation  of  the 
cross  effect  of  certain  injuries  and  diseases  of  the  brain. 


MEDULLA  OBLONGATA. 


199 


cend  and  are  joined  by  the  decussating  portion  from  the  opposite  side. 
Together  they  form  a prismatic  bundle  or  column  of  white  fibres, 
which  extends  deeply  into  the  substance  of  the  medulla,  and  is  trian- 
gular in  a cross  section,  (see  fig.  339,  b.) 

The  anterior  pyramids  contain  no  gray  matter. 

The  olioary  bodies  (olivEe,  seu  corpora  olivaria),  fig.  329,  c c,  are 
two  prominent  oval  masses  placed  to  the  outer  side  of  the  pyramids 
and  sunk  to  a considerable  depth  in  the  substance  of  the  medulla  ob- 
longata, appearing  on  its  surface  like  two  smooth  oval  eminences. 
They  are  placed  parallel  to  the  outer  border  of  the  pyramids,  and 
therefore  incline  outwards  towards  their  upper  end.  They  do  not 
reach  the  pons  Varolii  above,  being  separated  from  it  by  a deep  de- 
pression; nor  do  they  extend  so  far  in  a downward  direction  as  the 
pyramids,  than  which  they  are  considerably  shorter. 

The  olivary  bodies  consist  externally  of  white  substance,  of  which 
the  fibres  chiefly  run  longitudinally ; and  internally  of  a gray  nucleus, 
named  corpus  dentatum  or  ciliare. 

On  making  a section,  whether  horizontal  or  vertical,  this  gray  mat- 
ter which  is  of  a light  yellowish  colour,  appears  in  form  of  a zigzag 
line,  circumscribing  a whitish  substance  within,  and  interrupted  to- 
wards the  centre  of  the  medulla,  (see  figs.  339,  c,  340,  q).  The  gray 
matter  or  nucleus  of  the  olivary  body  therefore  is  arranged  in  the  form 
of  a pouch  or  capsule,  which  is  open  at  its  upper  and  inner  part  and 
has  its  sides  corrugated  or  plicated,  so  as  to  give  the  indented  appear- 
ance to  a section,  from  which  its  name  has  been  derived.  This  pouch 
is,  moreover,  surrounded-  with  white  matter  externally,  and  through 
its  open  part  white  fibres  pass  into  or  issue  from  its  interior,  and  con- 
nect it  with  other  parts  of  the  brain.  The  external  fibres  of  the  an- 
terior columns  of  the  cord,  which  are  here  thrown  outwards,  as  already 
mentioned,  are  continued  upwards,  on  the  surface  of  the  medulla  ob- 
longata, and  then  pass  partly  on  the  outside  and  partly  beneath  the 
olivary  bodies — being  joined  in  their  further  progress  by  the  fibres 
issuing  from  the  olivary  nucleus.  To  these  fibres  on  each  side,  the 
term  olivary  fasciculus  has  been  applied. 

The  restiform  bodies  (corpora  I'estiformia).  Behind  and  to  the  outer 
side  of  the  olivary  body,  are  two  lateral  rounded  eminences  or  columns, 
called  from  their  rope-like  appearance,  the  restiform  bodies,  fig.  329,  d d. 
These  are  directly  continuous  with  the  posterior,  and  with  part  of  the 
anlero-laleral  columns  of  the  cord;  they  diverge  slightly  as  they  as- 
cend, and  thus  occasion  the  great  width  of  the  medulla  at  its  upper 
part.  Eaoh  of  them  passes  into  the  corresponding  hemisphere  of  the 
cerebellum,  and  constitutes  its  inferior  peduncle. 

The  restiform  bodies  are  well  seen,  on  a posterior  view,  fig.  330,  d d. 
First,  they  are  in  contact  with  the  small  tracts  of  the  medulla,  named 
the  posterior  pyramids,  p ; but  higher  up  they  become  free  and  promi- 
nent, and  assist  in  forming  the  lateral  boundaries  of  the  fourth  ven- 
tricle. 

By  far  the  larger  portion  of  the  external  white  substance  of  the  res- 
tiform body  consists  of  longitudinal  fibres,  which  include  all  those  be- 
longing to  the  posterior  column  of  the  cord,  except  the  fasciculi 


200 


MEDULLA  OBLOJNGATA. 


graciles,  p,  some  derived  from  the  lateral  column,  and  also  a small 
band  from  the  anterior  column.  This  last-named  band,  fig.  329,/,  runs 
obliquely  below  the  olivary  body  and  connects  the  anterior  column 
•with  the  cerebellum,  as  was  first  shown  by  Mr.  Solly.* 

The  part  of  the  posterior  column  of  the  cord  which  belongs  to  the 
restifonn  body  of  the  medulla,  is  named  the  fasciculus  cuneatus  by 
the  German  anatomists : below  d,  on  the  right  side. 

There  is  a considerable  portion  of  gray  matter  in  the  interior  of  the 
restiform  body.  This  is  for  the  most  part  much  diffused ; but  one 
large  mass,  fig.  339,  d,  continuous  below  with  the  substantia  gelatinosa, 
or  gray  matter  forming  the  posterior  cornu  of  the  cord,  is  thrown  out 
towards  the  side  of  the  medulla,  and  generally  appearing  as  a longi- 
tudinal streak  at  the  surface,  forms  the  gray  tubercle  of  Rolando 
(tuberculo  cinereo). 

'i'he  posterior  pyramids  (fasciculi  graciles),  p p,  fig.  330,  of  the 
medulla  oblongata,  are  the  smallest  of  the  four  columns  into  which  it 
is  divided.  They  are  situated  in  contact  with  each  other,  one  on 
either  side  of  the  posterior  median  fissure.  They  consist  entirely  of 
white  fibres,  and  are  continuous  with  the  posterior  slender  tracts 
already  described  as  existing  on  the  posterior  median  aspect  of  the 
cord.  On  reaching  the  lower  part  of  the  medulla,  the  posterior  pyra- 
mids become  somewhat  swelled  out,  and  then,  diverging  from  one 
another,  they  become  closely  applied  to  the  restiform  bodies,  and  have 
been  considered  to  be  blended  with  them,  and  therefore  to  contribute 
to  form  the  inferior  peduncles  of  the  cerebellum.  But,  according  to 
Burdach  and  Arnold,  these  small  columns  ascend  to  the  cerebrum. 

The  triangular  portion  of  the  back' of  the  medulla,  which  is  bounded 
on  each  side  by  the  diverging  posterior  pyramids  below,  and  by  the 
restiform  bodies  higher  up,  constitutes  the  floor  of  the  fourth  ventricle, 
that  part  of  it,  namely,  which  is  called  the  calamus  scriptorius,  v\ 
Upon  it,  the  gray  matter  of  the  centre  of  the  medulla  oblongata  is,  as 
it  were,  opened  out  to  view.  It  is  marked  by  a median  furrow  v v', 
and  at  its  lower  end  is  a tubular  recess,  or  cul-de-sac,  passing  down 
the  centre  of  the  medulla  for  a few  lines.  This,  which  has  been  some- 
times named  the  ventricle  of  Arantius,  is  all  that  remains  in  adults  of 
the  central  canal  of  the  spinal  cord  already  spoken  of. 

In  the  upper  part  of  the  floor  of  the  ventricle  are  two  longitudinal 
eminences,  one  on  each  side  of  the  middle  furrow.  These  are  formed 
by  two  bundles  of  white  fibres,  mixed  with  much  gray  matter,  ihe  fas- 
ciculi teretes  of  some  authors,  les  faisceaux  innomines  of  Cruveilhier. 
They  seem  to  be  derived  from  part  of  the  lateral  columns  of  the  cord; 
Cruveilhier  believes,  however,  that  they  arise  from  the  gray  matter  at 
the  lower  end  of  the  medulla  oblongata. 

The  mode  in  which  the  columns  of  the  spinal  cord  are  re-arranged 
so  as  to  form  those  of  the  medulla  oblongata,  has  been  incidentally 
alluded  to  in  the  foregoing  description ; but  the  subject  will  be  here- 
after resumed  in  considering  the  internal  structure. 

Santorini,  and  subsequently  Rolando,  described  a set  of  superficial 


* Phil.  Trans,  for  May,  1836. 


THE  PONS  VAROLII. 


201 


white  fibres  on  the  fore  part  and  sides  of  the  medulla  oblongata, 
crossing  over  it  below  the  olivary  bodies.  From  their  direction  they 
were  named  fibrcB  vel  processus  arciformes,  fig.  329,  e.  They  belong 
to  a system  of  white  fibres  which  pass  transversely  or  horizontally, 
and  consequently  across  the  direction  of  the  longitudinal  columns 
already  described.  Part  of  them  run  from  behind  forwards  in  the 
median  plane,  forming  a sort  of  septum  between  the  lateral  halves  of 
the  cord,  and  have  been  named  septal  fibres,  fig.  340,  c.  It  is  proba- 
ble that  the  arciform  fibres  are  a continuation  of  these  central  fibres  in 
front ; and  there  is  also  reason  to  suppose  that  they  form  the  trans- 
verse medullary  while  striae,  in  the  floor  of  the  fourth  ventricle,  which 
are  connected  with  the  origin  of  the  auditory  nerves,  fig.  330,’'  and 
which  will  hereafter  be  described. 

Sometimes  the  greater  part  of  the  pyramidal  and  olivary  bodies  is 
covered  by  a thin  stratum  of  these  transverse  fibres,  which  appear  to 
issue  from  the  anterior  median  fissure ; but,  most  commonly,  these 
superficial  fibres  appear  only  at  the  lower  extremity  of  the  olive,  as 
the  arciform  fibres  already  mentioned.  These  differences  are,  most 
probably,  owing  not  to  the  presence  of  the  fibres  at  one  time,  and 
their  absence  at  another,  but  to  the  circumstance  of  their  running 
sometimes  superficially,  and  at  other  times  deeply  in  their  transverse 
course. 

THE  PONS  VAROLII,  OR  TUBER  ANNULARE. 

The  pons  Varolii,  or  annular  protuberance  (tuber  annulare),  fig. 
329,  p,  fig.  331,  0,  is  a comparatively  small  portion  of  the  encephalon, 
which  occupies  a central  position  on  its  under  surface,  above  and  in 
front  of  the  medulla  oblongata,  below  and  behind  the  crura  cerebri, 
and  between  the  middle  crura  of  the  cerebellum,  with  all  which  parts 
it  is  connected.  From  its  position  and  connexions  it  has  been  named 
meso-cephalon  (Chaussier),  and  nodus  encephali  (Rau,  Soemmerring). 

The  under  surface  of  the  pons  Varolii  is  of  course  seen  in  the  base 
of  the  brain,  fig.  331,  o,  w'hilst  its  upper  surface,  or  the  back,  continu- 
ous with  that  of  the  medulla  oblongata,  forms  part  of  the  floor  of  the 
fourth  ventricle,  fig.  330. 

The  under  surface  forms  a white  transverse  quadrangular  emi- 
nence, fig.  329,  p,  fig.  331,  0,  projecting  in  relief  beyond  the  level  of 
the  medulla  oblongata  and  crura  cerebri,  which,  as  we  shall  see,  are 
connected  wdth  each  other  through  its  substance.  It  is  this  part,  in 
particular,  which  is  named  the  annular  protuberance,  because  it  em- 
braces, as  in  a ring,  the  longitudinal  portions  of  the  nervous  axis, — and 
also  the  pons,  because,  when  viewed  from  below,  it  seems  to  cross 
over  those  parts  like  a bridge. 

It  rests  on  the  upper  part  of  the  basilar  groove.  It  is  marked  with 
transverse  bands  and  striae,  w'hich  indicate  the  course  of  its  superficial 
fibres.  Along  the  middle  line  it  presents  a shallow  longitudinal 
groove,  which  is  wider  in  front  than  behind,  and  is  prolonged  over  the 
anterior  and  posterior  borders  of  the  pons.  The  basilar  artery  runs 
along  this  groove,  in  the  floor  of  which  are  perforations  for  the  trans- 
mission of  small  branches  of  that  vessel. 

The  anterior  and  posterior  borders  of  the  pons  are  well  defined. 


202 


THE  CEREBRUM. 


The  anterior  is  more  extended  than  the  posterior,  and  its  outline  is 
more  convex  from  side  to  side. 

Tlie  crura  cerebri,  fig.  331,  d,  t,  appear  to  emerge  from  beneath  it. 
At  the  sides,  the  limits  of  the  pons  Varolii  are  quite  arbitrary,  for  it 
merely  becomes  narrower  owing  to  its  being  gathered,  as  it  were, 
into  a compressed  bundle  on  each  side  1.  These  two  bundles  pass 
obliquely  outwards  and  backwards  into  the  cerebellum,  and  form  its 
middle  peduncles. 

The  substance  of  the  pons  Varolii  consists  of  transverse  and  longi- 
tudinal white  fibres  interspersed  with  a quantity  of  diffused  giay 
matter.  The  transverse  fibres,  with  a few  exceptions  to  be  particu- 
larized hereafter,  enter  the  cerebellum  under  the  name  of  the  middle 
crura  or  peduncles,  and  form  a commissural  system  for  its  two  hemi- 
spheres. The  longitudinal  fibres  are  those  which  ascend  from  the 
medulla  oblongata  into  the  crura  cerebri,  augmented,  it  would  seem, 
by  others  which  arise  within  the  pons  from  the  gray  matter  scattered 
through  it.  The  arrangement  of  both  these  sets  of  fibres  in  the  inte- 
rior of  the  pons  will  be  referred  to  hereafter ; but  we  may  notice  now 
the  layer  of  transverse  fibres,  fig.  329,  which  are  next  the  surface. 
The  fibres  composing  this  layer  do  not  all  run  parallel  to  each  other. 
The  middle  fibres  pass  directly  across,  the  lower  set  ascend  slightly, 
whilst  the  upper  fibres,  which  are  the  most  curved,  descend  obliquely 
to  reach  the  crura  cerebelli  on  each  side.  There  is  always  one  super- 
ficial band,  i,  of  the  superior  fibres,  which  crosses  obliquely  down- 
W'ards  over  the  middle  and  lower  fibres,  to  gain  the  anterior  surface 
of  the  corresponding  crus. 

THE  CEREBRUM. 

The  cerebrum  or  brain  proper,  fig.  328,  a,  as  already  mentioned,  is 
the  highest,  and  by  far  the  largest  portion  of  the  encephalon.  It  is  of 
an  ovoid  shape,  but  is  irregularly  flattened  on  its  under  side.  It  is 
placed  in  the  cranium  with  its  small  end  forw'ards,  its  greatest  width 
being  opposite  to  the  parietal  eminences. 

The  cerebrum  consists  of  two  lateral  halves,  or  hemi spheres,  a.s  they 
are  called,  which,  though  connected  by  a median  portion  of  nervous 
substance,  are  separated  in  a great  part  of  their  extent  by  a fissure, 
named  the  great  longitudinal  fissure,  which  is  seen  on  the  upper  sur- 
face of  the  brain  and  partly  also  upon  its  base,  fig.  331,  a x b. 

The  cerebral  hemispheres  are  not  plain  and  uniform  upon  the  sur- 
face, but  are  moulded  into  numerous  smooth  and  tortuous  eminences, 
named  convolutions  or  gyri,  which  are  marked  off  from  each  other  by 
deep  furrows,  called  sulci,  or  anfractuosities.  These  convolutions  are 
coloured  externally;  for  the  surface  of  the  cerebral  hemispheres,  un- 
like the  parts  hitherto  described,  is  composed  of  gray  matter. 

Upper  surface  of  the  cerebrum. — The  great  longitudinal  fissure,  seen 
upon  the  upper  surface  of  the  brain,  extends  from  before  backwards 
throughout  its  whole  length  in  the  median  plane,  and  thus  separates 
the  cerebrum,  as  already  stated,  into  a right  and  left  hemisphere.  On 
opening  this  fissure,  it  is  seen,  both  before  and  behind,  to  pass  quite 
through  to  the  base  of  the  cerebrum  ; but  in  the  middle  it  is  interrupted 
by  a transverse  portion  of  white  substance,  named  the  corpus  callosum, 


THE  CEREBRAL  LOBES. 


203 


fig.  332,  a h,  which  connects  the  two  hemispheres  together.  In  the 
natural  state,  this  fissure  is  occupied  by  a vertical  process  of  the  dura 
mater — the  falx  cerebri, — which  dips  down  between  the  two  hemi- 
spheres, not  quite  reaching  to  the  corpus  callosum. 

Each  cerebral  hemisphere  has  an  outer  or  convex  surface,  which  is 
in  contact  with  the  vault  of  the  cranium,  an  inner  or  flat  surface,  of  a 
crescent  shape,  which  forms  one  side  of  the  longitudinal  fissure ; and 
an  irregular  under  surface,  which  rests  on  the  base  of  the  skull,  and 
on  the  tentorium  cerebelli. 

Under  surface  of  cerebrum. — The  under  surface  of  each  hemi- 
sphere, fig.  331,  is  marked  off  into  three  parts,  called  lobes,  which  are 
named  according  to  their  position,  anterior,  middle,  and  posterior,  a b 
c,  also/g  h,  fig.  328.  The  division  between  the  anterior  and  middle 
lobes,  which  is  very  distinct,  is  indicated  by  a deep  cleft,  named  the 
Sylvian  fissure,  s s'.  There  is  no  such  evident  demarcation  between 
the  middle  and  posterior  lobes ; but  anatomists  have  considered  as 
the  posterior  lobe,  that  part  of  the  hemisphere  which  lies  over  the 
cerebellum.*  The  under  surface  of  the  anterior  lobe  is  triangular  and 
excavated  to  adapt  it  to  the  roof  of  the  orbit  on  which  it  rests.  The 
middle  lobe,  fig.  328,  g,  is  rounded  and  prominent,  and  occupies  the 
middle  fossa  of  the  skull — the  edge  of  the  lesser  wing  of  the  sphenoid 
bone  corresponding  with  the  Sylvian  fissure.  The  posterior  lobe,  h,  is 
smooth  and  slightly  concave  on  its  under  surface,  where  it  rests  on  the 
arch  of  the  tentorium. 

The  Sylvian  fissure,  fig.  328,  e,  331,  s s',  which  separates  the  ante- 
rior and  middle  lobes,  passes  at  first  upwards  and  backwards  in  the 
outer  part  of  the  hemisphere,  and  divides  into  two  branches.  At  the 
entrance  of  the  fissure  is  seen  a bundle  of  white  substance  passing 
from  the  anterior  to  the  middle  lobe,  named  fasciculus  unciformis 
(Reil). 

On  opening  the  fissure  out,  there  is  exposed  to  view  a triangular 
prominent  portion  of  the  cerebral  mass,  named  the  island  of  Reil 
(insula).  It  is  marked  by  small  and  short  convolutions,  which  are 
sometimes  called  gyri  operti,  because  in  the  natural  state  of  the  parts 
they  are  covered  by  the  sides  of  the  fissure. 

It  has  already  been  stated  that  the  entire  surface  of  the  cerebral 
hemispheres  is  marked  by  convolutions  and  sulci,  some  of  which,  it 
must  not  be  forgotten,  are  concealed  from  view  in  the  great  fissures. 
These  convolutions  do  not  exactly  resemble  each  other  in  all  brains, 
nor  are  they  symmetrical  on  the  two  sides  of  the  same  brain,  although 
there  is  a certain  correspondence  in  their  general  direction. 

Each  convolution  may  be  described  as  presenting  a summit  or 
rounded  free  border,  two  sides,  and  a base,  by  which  it  is  connected 
with  the  general  cerebral  mass.  The  outer  portion  of  the  convolutions 
(including,  of  course,  the  sides  and  bottom  of  the  sulci)  consists  of  a 
layer  of  gray  matter,  which  is  here  called  the  cortical  substance  or 
layer:  they  are  covered  closely  throughout  by  the  pia  mater,  a vascu- 
lar membrane,  which  sends  processes  down  to  the  bottom  of  the  sulci 
between  them.  These  sulci  are  generally  about  an  inch  deep ; but  in 

* It  is  right  to  remark  that  some  anatomical  writers  admit  only  two  lobes,  reckoning  the 
middle  and  posterior  lobes  as  a single  one,  under  the  name  of  the  posterior  lobe. 


204 


THE  CEREBRUM. 


this  respect  there  is  much  variety  in  different  brains,  and  in  different 
parts  of  the  same  brain;  in  other  words,  the  depth  of  the  convolutions 
varies  considerably:  those  upon  the  outer  convex  surface  of  the  hemi- 
sphere are  the  deepest.  In  general,  the  depth  of  a convolution  exceeds 
its  width;  and  its  width,  near  the  summit,  is  greater  than  through  its 
base. 

The  free  border  of  a large  convolution,  or  the  side  of  an  unusually 
deep  one,  is  sometimes  grooved  longitudinally,  or  marked  with  shal- 
low notches,  so  as  to  be  partially  divided  into  smaller  or  subordinate 
gyri.  All  the  convolutions  are  continuous  with  each  other,  if  not 
upon  the  surface,  at  least  within  the  anfractuosities ; for,  if  one  ap- 
pears to  end  abruptly,  it  will  be  found  on  examination  to  sink  between 
and  then  run  into  others,  across  the  bottom  of  the  intervening  sulci. 

Since  the  external  gray  or  cortical  substance  is  continuous  over  the 
whole  surface  of  the  cerebral  hemispheres,  being  found  alike  within 
the  sulci  and  upon  the  gyri,  a far  greater  extent  of  gray  matter  is 
obtained  with  a given  size  of  the  organ  than  could  have  been  the  case, 
had  the  hemispheres  been  plain  and  destitute  of  convolutions. 

The  general  arrangement  of  the  convolutions  has  been  made  the 
subject  of  study  by  various  anatomists  in  earlier  and  recent  times,  but 
much  yet  remains  to  be  elucidated.  An  attempt  to  describe  individual 
gyri  would  be  quite  useless,  owing  to  their  irregularity  in  different 
cases,  and  their  want  of  symmetry  in  the  same  brain.  Nevertheless, 
there  are  some  sufficiently  constant  in  presence,  and  characteristic  in 
situation  and  form,  to  admit  of  being  specially  described. 

It  has  also  been  shown  that  certain  of  the  cerebral  convolutions 
precede  others  in  their  appearance  in  the  series  of  mammiferous  ani- 
mals; for  in  the  lowest  mammalia,  and  in  all  inferior  classes  of  verte- 
brata,  the  cerebrum  is  not  convoluted  on  the  surface. 

Among  the  earliest  convolutions  to  appear  are  those  of  the  island 
of  Red,  which  are  concealed  in  the  Sylvian  fissure.  As  seen  in  the 
human  brain,  they  radiate  from  the  summit  to  the  base  of  the  triangu- 
lar eminence  formed  by  the  island,  and  are  separated  by  shallow  sulci. 

Surrounding  the  convolutions  of  the  island  (gyri  operti),  and  forming 
the  lips  of  the  Sylvian  fissure,  is  a very  large  convolution,  named  con- 
volution of  the  Sylvian  fissure.  This  is  also  early  in  its  appearance  in 
animals:  in  them  it  is,  at  first,  simple  in  form,  and  completely  sur- 
rounds the  fissure,  forming  a curve,  open  in  front  and  below.  In  the 
human  brain,  fig.  33l,fifi,  it  is  tortuous  and  much  folded,  so  as  to  form 
many  subordinate  gyri,  corresponding  with  the  front,  upper,  and  under 
border  of  the  fissure.  The  commencement  of  this  convolution,/,  in 
front  of  the  fissure,  forms  the  outer  part  of  the  triangular  orbital 
surface  of  the  anterior  lobe.  From  its  outer  border  proceed  nu- 
merous secondary  gyri,  which  extend  in  various  directions  on  the 
convex  surface  of  the  hemisphere,  fig.  328;  and  its  inner  border 
receives,  in  a similar  manner,  the  radiating  convolutions  of  the  island 
of  Reil. 

Perhaps  the  most  distinct  and  symmetrical  convolution  in  the  whole 
brain  is  that  named  the  internal  convolution,  convolution  of  the  corpus 
callosum,  gyrus  fornicatus.  Commencing  (fig.  332,  h),  on  the  under 
surface  of  the  brain,  immediately  before  the  part  named  the  anterior 


THE  CONVOLUTIONS. 


205 


perforated  space,  it  ascends  a short  distance  in  front  of  the  anterior 
recurved  extremity  of  the  corpus  callosum,  a,  and  then  runs  back- 
wards, h'  immediately  above  that  body,  as  far  as  its  posterior  ex- 
tremity: there  it  turns  downwards  and  forwards,  A",  embracing  the 
cerebral  peduncle,  fig.  331,  t,  to  reach  the  entrance  of  the  Sylvian 
fissure,  h'.  This  long  convolution,  therefore,  describes  a sort  of  ring 
open  or  interrupted  opposite  the  Sylvian  fissure,  and  embracing  the 
corpus  callosum  above,  and  the  cerebral  peduncle  below.  It  thus 
occupies  the  entire  margin  of  the  convoluted  surface  of  the  hemi- 
sphere, and,  as  was  pointed  out  by  Foville,  forms  a sort  of  rim  or 
border  to  the  gray  matter,  whence  it  is  named  by  him  convolution 
d’ourlet.  The  surface  of  this  convolution,  especially  towards  its 
termination  below,  is  covered'  by  a very  thin  cribriform  layer  of  white 
substance,  which,  with  the  gray  matter  beneath,  gives  the  surface  a 
mottled  aspect.  This  has  been  called  the  reticulated  white  substance. 
The  gyrus  fornicatus  is  variously  grooved  in  different  brains,  and 
from  its  upper  border  are  given  off  secondary  gyri,  which  extend  in 
different  directions  upon  the  inner  or  flat  surface  of  the  hemisphere, 
fig.  332.  From  the  appearance  of  the  convolution  and  its  offsets 
in  this  situation,  the  name  processo  cristato  was  applied  to  it  by 
Rolando. 

Another  large  convolution  may  be  traced,  according  to  Foville, 
more  or  less  indented  or  interrupted,  however,  in  its  course,  along  the 
line  of  junction  between  the  convex  and  flat  surfaces  of  the  hemi- 
sphere,— in  other  words,  along  the  corresponding  lip  of  the  great 
longitudinal  fissure.  This,  which  might  be  called  the  marginal  convo- 
lution of  the  longitudinal  fissure,  commences  on  the  under  surface  of 
the  brain  (figs.  331,  332,  x),  in  common  with  the  gyrus  fornicatus,  and 
passing  forwards,  forms  the  inner  border  of  the  triangular  orbital 
surface  of  the  anterior  lobe,  and  is  here  cleft  as  it  were  into  two  by  a 
deep  sulcus,  into  which  the  olfactory  nerve  1,  is  received.  Turning 
next  over  the  front  and  upper  surface  of  the  cerebrum,  it  may  gene- 
rally be  traced  for  some  distance  along  the  margin  of  the  longitudinal 
fissure  x'  x",  but  soon  becomes  marked  by  deep  sulci ; and  thus  inter- 
rupted, may  be  followed  round  the  posterior  extremity  y,  and  after- 
wards along  the  under  surface  of  the  hemisphere  forwards  as  far  as 
the  point  of  the  middle  lobe,  running  parallel  for  some  space  with  the 
under  portion  of  the  gyrus  fornicatus. 

The  convolutions  on  the  under  surface  of  the  anterior  lobe  have 
been  usually  mentioned  separately  by  anatomists.  The  outer  border, 
fig.  331,  of  this  triangular  surface  is  formed  by  the  commencement  of 
the  convolution  of  the  Sylvian  fissure  f;  the  inner  border,  x,  by  the 
marginal  convolution  of  the  longitudinal  fissure,  in  the  sulcus  on  which 
the  olfactory  nerve  is  lodged.  The  intermediate  excavated  part  is 
occupied  by  other  convolutions,  less  regular  in  their  direction.  At  the 
apex  of  the  triangle  behind,  the  two  borders  are  connected  by  a short 
and  but  slightly  elevated  convolution,  s,  which  bounds  the  anterior 
perforated  space  in  front. 

It  remains  only  to  notice  those  gyri  which  occupy  the  outer  or 
convex  surface  of  the  hemisphere,  between  the  marginal  convolution 

VOL.  II.  18 


206 


THE  CONVOLUTIONS. 


of  the  longitudinal  fissure  and  that  of  the  Sylvian  fissure.  The  general 
direction  of  these,  see  fig.  328,  f h g,  which  are  the  largest,  the  most 
complicated,  and  the  least  symmetrical  of  all  the  convolutions  of  the 
human  brain,  is  not  longitudinal,  like  those  previously  described,  but 
transverse  or  somewhat  oblique.  It  has  been  remarked  by  Foville 
that  they  frequently  become  branched  like  the  letter  Y,  as  they  proceed 
upwards  and  backwards  towards  the  longitudinal  fissure. 

M.  Foville  considers  that  the  convolutions  may  be  arranged  into  four  principal 
groups  or  orders,  founded  in  a great  measure  on  their  relative  connexions  with 
the  anterior  perforated  space,  which,  in  his  estimation,  is  a part  of  the  highest 
importance. 

The  first  order  issues  from  the  perforated  space,  and  consists  of  two  portions. 
One,  large  and  vertical,  is  the  gyrus  fornicatus,  minus  its  ascending  secondary 
gyri ; the  other,  short  and  horizontal,  is  the  slightly  elevated  ridge  which  bounds 
the  perforated  space,  in  front  and  on  the  outer  side. 

The  second  order,  also  consisting  of  two  portions,  commences  from  the  hori- 
zontal portion  of  the  first  order,  on  the  limits  of  the  perforated  space.  One  part 
corresponds  with  the  marginal  convolution  of  the  longitudinal  fissure,  as  already 
described,  except  that  part  of  it  on  the  orbital  surface  of  the  anterior  lobe,  which 
lies  to  the  outer  side  of  the  olfactory  sulcus ; the  other  part  is  the  convolution  of 
the  Sylvian  fissure. 

The  third  order  consists  of  two  sets,  of  which  one  occupies  the  inner  surface  of 
the  hemisphere,  and  connects  the  gyrus  fornicatus  in  its  whole  length  with  the 
marginal  convolution  of  the  longitudinal  fissure  ; the  other  set  lies  in  the  Sylvian 
fissure,  forms  the  islaud  of  Reil,  and  connects  the  short  horizontal  portion  of  the 
first  order  with  the  convolution  surrounding  that  fissure. 

The  convolutions  of  the  fourth  order,  the  largest,  deepest,  and  least  symmetrical 
of  all,  are  quite  detached  from  the  perforated  space,  and  have  no  relation  to  the 
first  order  of  convolutions.  They  connect  the  two  convolutions  of  the  second  order 
together,  viz.,  the  marginal  convolution  of  the  median  fissure  and  that  of  the  Syl- 
vian fissure,  and  occupy  the  outer  or  convex  surface  of  the  cerebral  hemisphere. 

M.  Leuret  has  arrived  at  some  interesting  conclusions  in  reference  to  the  cere- 
bral convolutions  in  mammalia,  which  class  of  animals  are  arranged  by  him,  in 
connexion  with  this  point,  into  as  many  as  fourteen  groups. 

In  the  lowest  group — represented  by  the  bat,  mole,  rat,  &c. — the  cerebral  hemi- 
spheres, as  in  birds,  are  quite  plain  and  smooth,  though  divided  by  a Sylvian 
fissure.  In  the  second  group — including  the  rabbit,  beaver,  and  porcupine — that 
fissure  is  more  strongly  marked  3 but  there  are  only  a few  slight  depressions  on 
the  surface  of  the  hemispheres,  indicating  the  future  sulci  between  the  convo- 
lutions. 

In  the  third  group — formed  by  the  fox,  wolf,  and  dog — the  simplest  form  of 
true  convolutions  is  first  met  with ; and  they  are  named  by  M.  Lemet,fiindam,ental. 
convolutions.  In  the  brain  of  the  fox,  taken  as  a typical  example,  they  are  six  in 
number ; they  are  all  simple  in  outline,  distinct  from  each  other,  and  form  a series 
of  longitudinal  curved  lines  on  the  surface  of  the  hemisphere,  running  from  before 
backwards. 

Four  of  them,  named  external,  are  placed  on  the  convex  surface  of  the  hemi- 
sphere. Of  these,  one  forms  the  curved  lip  or  border  of  the  Sylvian  fissure,  and 
surrounds  the  island  of  Red;  the  other  three,  also  curved  in  this  direction,  are 
placed  parallel  with  the  first,  and  one  above  another, — the  fourth,  or  superior  con- 
volution, being  placed  on  the  margin  of  the  longitudinal  fissure.  The  fifth  con- 
volution {anterior)  forms  the  under  and  fore  part  of  the  anterior  lobe,  and  is  named 
the  supra  orbital  convolution.  The  sixth  {internal)  is  placed  above  the  corpus 
callosum,  and  corresponds  with  the  gyrus  fornicatus. 

In  the  succeeding  groups,  up  to  the  thirteenth,  various  changes  take  place  in 
the  condition  and  mode  of  connexion  of  these  fundamental  convolutions,  which 
cannot  be  detailed  here.  Thus,  in  all  cases  excepting  in  the  feline  tribe,  they 
are  reduced  in  number  to  five,  or  four — the  reduction  affecting  the  external  con- 
volutions. In  some  cases  they  are  bifurcated  at  certain  points,  or  marked  by 


BASE  OF  THE  CEREBRUM. 


207 


divisions  or  depressions,  or  they  are  undulated  in  their  course.  Lastly,  they  are 
very  commonly  united,  at  more  or  less  frequent  intervals,  by  short  supplementary 
convolutions. 

In  the  brain  of  the  elephant  (which  stands  in  the  thirteenth  group)  M.  Leuret 
recognises  another  additional  set  of  convolutions,  which  have  a more  decidedly 
transverse  direction  than  the  short  supplementary  convolutions  above  alluded  to. 
These  new  convolutions  {superior  transverse),  forming  two  rows  and  separated 
by  a groove,  occupy  the  upper  and  outer  part  of  the  hemisphere,  and  cross  or  in- 
terrupt, as  it  were,  the  fundamental  longitudinal  convolutions. 

In  the  last  group  (that  of  the  monkeys)  these  superior  transverse  convolutions, 
forming  two  distinct  rows,  separated  by  an  intermediate  groove,  are  still  more 
evident. 

In  the  human  cerebrum,  M.  Leuret,  by  help  of  a comparison  between  the  brain 
of  the  fcEtus  and  the  adult,  has  represented  three  external  fundamental  convolu- 
tions, which  are  toiluous,  and  frequently  communicate  with  each  other.  Besides 
these,  there  is  the  internal  convolution  (gyrus  fomicatus)  and  supra-orbital  con- 
volution (?). 

Between  the  anterior  and  posterior  portions  of  the  three  external  convolutions, 
are  interposed,  on  the  upper  surface  of  the  brain,  two  sets  of  transverse  convolu- 
tions, divided  by  a distinct  sulcus,  which  runs  outwards  and  forwards  from  the 
longitudinal  fissure,  so  that  the  right  and  left  grooves  form  a V-shaped  line,  open 
in  front.  This  fissure,  also  noticed  in  the  brains  of  the  elephant  and  monkey,  is 
stated  by  Leuret  to  be  very  constant,  and  is  named  by  him  the  fissure  of  Rolando.* 

From  the  preceding  account  of  the  cerebral  convolutions,  it  would 
appear  that  those  situated  upon  the  outer  or  convex  surface  of  the 
hemisphere — the  fourth  order  of  M.  Foville,  and  the  superior  transverse 
convolutions  of  M.  Leuret — attain  their  highest  development  in  man, 
and  are  indeed  particularly  characteristic  of  the  human  brain.  To 
this  peculiarity,  however,  must  be  added,  the  elongation  of  the  cere- 
brum backwards  by  the  increased  development  of  the  posterior  lobe, 
and  the  greater  complexity  of  the  vertical  convolutions  in  the  median 
fissure,  and  of  those  of  the  island  of  Reil. 

Base  of  the  cerebrum,  fig.  331. — When  the  brain  is  turned  with  its 
base  uppermost,  and  the  parts  of  which  it  is  composed  are  allowed  to 
fall  asunder  by  their  own  weight,  two  large  bundles,  d,  t,  consisting 
of  white  substance  externally,  are  seen  to  emerge  together  from  the 
fore  part  of  the  pons  Varolii,  o,  and,  separating  from  each  other  as 
they  proceed  forwards  and  outwards,  to  enter  the  inner  and  under 
part  of  the  right  and  left  cerebral  hemispheres.  These  white  bundles, 
which  are  marked  on  the  surface  with  longitudinal  strim,  are  the  pe- 
duncles (crura)  of  the  cerebrum.  Just  before  entering  the  correspond- 
ing hemisphere,  each  is  crossed  by  a flattened  white  cord,  named  the 
optic  tract,  u u,  which,  adhering  by  its  upper  border  to  the  peduncle, 
is  directed  forwards  and  inwards,  and  meets  in  front  with  its  fellow 
of  the  opposite  side  to  form  the  optic  commissure,  c,  from  the  fore  part 
of  which  the  optic  nerves  2,  2,  proceed. 

Limited  behind  by  these  diverging  peduncles,  and  in  front  by  the 
converging  optic  tracts,  is  a lozenge-shaped  interval,  called  the  inter- 
peduncular space,  in  which  are  found  the  following  parts  : — the  poste- 

* In  the  Hunterian  Lectures  for  1842,  Professor  Owen  gave  the  results  of  his  observa- 
tions  on  the  comparative  anatomy  of  the  convolutions.  He  had  previously,  in  1833,  called 
attention  to  this  study  as  a means  of  determining  “the  amount  and  locality  of  the  convo- 
lutions of  the  human  brain  which  are  analogous  to  those  of  the  lower  animals.”  On  the 
anatomy  of  the  Cheetah  ; Zoological  Trans,  vol.  i. 


208 


THE  CEREBRUM. 


riol-  perforated  space,  the  corpora  albicantia,  the  tuber  cinereum, 
infundibulum,  and  pituitary  body. 


Fig.  331. 


Shows  the  under  surface  or  base  of  the  encephalon  freed  from  its  membranes — a,  anterior,  e, 
middle,  and  c,  posterior  lobe  of  cerebrum. — a.  The  fore  part  of  the  great  longitudinal  fissure,  h. 
Notch  between  hemispheres  of  the  cerebellum,  c.  Optic  commissure,  d.  Left  peduncle  of  cere- 
brum. e.  Posterior  perforated  space,  e to  i.  Interpeduncular  space,  /y'.  Convolution  of  Syl- 
vian fissure,  li.  Termination  of  gyrus  fornicatus  behind  the  Sylvian  fissure,  i.  infundibulum. 
1.  Right  middle  crus  or  peduncle  of  cerebellum,  m m.  Hemispheres  of  cerebellum,  n.  Corpora 
albicantia.  o.  Pons  Varolii,  continuous  at  each  side  with  middle  crura  of  cerebellum,  jt.  Ante- 
rior perforated  space,  Horizontal  fissure  of  cerebellum,  r.  Tuber  cinereum.  .«  s'.  Sylvian 
fissure,  t.  Left  peduncle  or  crus  of  cerebrum,  u u.  Optic  tracts,  v.  Medulla  oblongata,  x. 
Marginal  convolution  of  the  longitudinal  fissure. — 1 to  9 indicate  the  several  pairs  of  cerebral 
nerves,  numbered  according  to  the  usual  notation,  viz.,  1.  Olfactory  nerve,  2,  Optic.  3. 
Motor  nerve  of  eye.  4.  Pathetic.  5.  Trifacial.  6.  Abducent  nerve  of  eye.  7.  Auditory,  and  3'. 
Facial.  8.  Glosso-pharyngeal,  8'.  Vagus,  and  8".  Spinal  accessory  nerve. 

Immediately  in  front  of  the  pons  is  the  posterior  perforated  space 
(locus  perforatus  posterior),  e,  a deep  fossa  situated  between  the  pe- 
duncles, the  bottom  of  which  is  composed  of  grayish  matter,  connect- 
ing the  diverging  crura  together,  and  named  pons  Tarini.  It  is  perfo- 
rated by  numerous  small  openings  for  the  passage  of  blood-vessels ; 
and  some  horizontal  white  striae  usually  pass  out  of  the  gray  matter 
and  turn  round  the  peduncles  immediately  above  the  pons. 

In  front  of  this  fossa  are  two  round  white  eminences,  each  about 
the  size  of  a pea,  placed  one  on  either  side,  surrounded  by  gray 
matter,  and  connected  together  across  the  middle  line.  These  white 
bodies  {corpora  albicantia — corp.  mammillaria),  rt,  are  formed,  as  will 
hereafter  be  seen,  by  the  anterior  extremities  of  the  fornix,  a part 
situated  in  the  interior  of  the  brain  : hence  they  have  also  been  named 
bulbs  of  the  fornix.  In  the  foetus  they  are  at  first  blended  together, 


THE  CEREBRUM. 


209 


and  become  separated  about  the  beginning  of  the  seventh  month.  In 
most  vertebrate  animals  there  is  but  one  white  eminence,  or  corpus 
albicans,  in  this  position. 

The  interval  between  the  corpora  albicantia  and  the  optic  tracts  is 
occupied  by  a soft  and  slightly  prominent  mass  of  gray  substance,  the 
tuher  cinereum  (Soemmerring),  r,  which  is  connected  with  the  sur- 
rounding parts  of  the  cerebrum,  and  shuts  in  the  third  or  middle  ven- 
tricle below,  forming  part  of  what  is  termed  the  floor  of  that  cavity. 
From  the  middle  of  the  tuber  cinereum  is  prolonged  a conical  process 
of  a reddish  colour,  directed  downwards  and  forwards,  and  about 
two  lines  in  length,  named  the  infundibulum,  i,  also  fig.  332,  i,  to  the 
summit  of  which  is  attached  the  pituitary  body,  p.  This  gray  pro- 
longation, from  the  tuber  cinereum,  is  hollow  at  its  base,  and  for  a 
short  distance  downwards,  and  its  cavity  communicates  above  with 
the  third  ventricle — whence  its  name  infundibulum  (funnel). 

The  pituitary  body,  fig.  332,  p,  formerly  called  pituitary  gland,  from 
its  being  erroneously  supposed  to  discharge  pituita  into  the  nostrils,  is 
a small  reddish-gray  mass,  of  a somewhat  flattened  oval  shape,  being 
widest  in  the  transverse  direction.  In  the  natural  position  of  the  brain 
it  occupies  the  sella  turcica  of  the  sphenoid  bone.  It  consists  of  two 
lobes,  of  which  the  anterior  is  larger,  and  concave  behind,  where  it 
embraces  the  smaller  posterior  lobe.  Its  weight  is  from  five  to  ten 
grains.  In  the  adult  it  is  solid,  and  its  general  structure  is  firm. 

The  anterior  lobe  consists  of  two  kinds  of  matter,  one  hard  and 
gray,  the  other,  situated  within,  softer  and  of  a yellowish-white  colour. 
The  posterior  lobe  is  darker  and  redder  than  the  anterior.  Both  are 
very  vascular ; but  they  have  no  ducts,  nor,  indeed,  any  other  glandu- 
lar character. 

In  the  foetus,  the  pituitary  body  is  proportionally  large,  and  contains 
a cavity  which  communicates,  through  that  of  the  infundibulum,  with 
the  third  ventricle. 

The  tuber  cinereum,  as  already  mentioned,  is  bounded  before  by  the 
optic  commissure,  which,  together  with  the  optic  tracts,  will  be  fully 
noticed  under  the  description  of  the  optic  nerve. 

Still  confining  our  attention  to  the  parts  in  the  middle  line  of  the 
base  of  the  brain,  we  observe  in  front  of  the  optic  commissure,  the 
anterior  portion  of  the  great  longitudinal  fissure,  which  reaches  down 
between  the  hemispheres  in  this  situation.  At  a short  distance  in  front 
of  the  commissure,  this  fissure  is  crossed  by  a white  transverse  mass, 
which  is  the  anterior  recurved  extremity  of  the  corpus  callosum.  On 
gently  turning  back  the  optic  commissure,  a thin  connecting  layer  of 
gray  substance,  the  lamina  cinerea,  fig.  332,  behind  h,  is  seen  proceed- 
ing backwards  from  the  corpus  callosum  to  the  commissure,  to  become 
continuous  (supposing  the  parts  in  their  natural  position)  above  the 
commissure  with  the  gray  matter  of  the  tuber  cinereum.  This  thin 
gray  layer,  which  is  also  connected  at  the  sides  with  the  gray  substance 
of  the  anterior  perforated  space  to  be  presently  described,  forms  part 
of  the  anterior  boundary  of  the  third  ventricle:  it  is  very  generally- 
torn  in  removing  the  brain  from,  the  skull ; and  in  that  case,  an  aper- 
ture is  made  into  the  fore  part  of  the  third  ventricle. 

18* 


210 


INTERNAL  PARTS  OF  CEREBRUM. 


In  front  of  the  optic  tract,  and  near  the  entrance  of  the  Sylvian 
fissure,  there  is  situated  a grayish  quadrangular  space  on  each  side, 
named  tlie  anterior  'perforated  space  (locus  perforatus  amicus),  fig. 
33 1 , p p. 

Each  anterior  perforated  space  is  bounded  in  front  by  the  convolu- 
tions of  the  anterior  cerebral  lobe,  on  which  are  seen  the  roots  of  the 
olfactory  nerve,  1 ; behind,  by  the  optic  tract ; on  the  outer  side,  by 
the  middle  lobe,  and  the  commencement  of  the  Sylvian  fissure;  and 
on  the  other  side  by  the  median  fissure  and  the  lamina  cinerea.  It  is 
placed  immediately  beneath  the  corpus  striatum,  a large  mass  of  gray 
matter  in  the  interior  of  the  brain,  to  be  hereafter  noticed.  The  gray 
surface  of  each  perforated  space  is  crossed  by  a broad  white  band, 
which  may  be  traced  from  the  middle  of  the  under  surface  of  the 
corpus  callosum  in  front,  backwards  and  outwards  along  the  side  of 
the  lamina  cinerea  towards  the  entrance  of  the  Sylvian  fissure.  These 
bands  on  the  two  sides  are  named  Ihe  peduncles  of  the  corpus  callosum. 
The  anterior  perforated  space,  especially  that  part  of  it  next  the 
Sylvian  fissure,  is  pierced  with  a multitude  of  small  holes  for  the 
passage  of  blood-vessels,  most  of  which  are  destined  for  the  corpus 
striatum. 

When  the  entire  encephalon  is  viewed  from  below  (as  in  fig.  331), 
the  back  part  of  the  under  surface  of  the  cerebrum  is  concealed  by 
the  cerebellum,  m,  and  the  pons  Varolii,  o.  If,  however,  these  parts 
be  removed,  it  will  be  seen  that  the  two  hemispheres  of  the  cerebrum 
are  separated  behind  as  they  are  in  front,  by  the  descent  of  the  great 
longitudinal  fissure  between  them,  and  this  fissure  is  arrested  by  a cross 
mass  of  white  substance,  forming  the  posterior  end  of  the  corpus  cal- 
losum. This  posterior  part  of  the  great  longitudinal  fissure  is  longer 
than  the  anterior  portion. 

INTERNAL  PARTS  OF  THE  CEREBRUM. 

Having  completed  the  survey  of  the  parts  seen  extei’nally  upon  the 
cerebrum,  we  proceed  to  examine  its  internal  anatomy.  This  will  be 
more  readily  understood  in  detail,  if  some  general  idea  be  previously 
obtained  of  it. 

The  hemispheres,  it  will  be  remembered,  are  connected  together  in 
the  middle  by  the  corpus  callosum,  and  it  is  obvious  that  the  structures 
filling  up  the  interpeduncular  space,  serve  also  as  connecting  media. 
Between  the  corpus  callosum  above  and  the  peduncles  below,  the  two 
hemispheres  are  partially  separated  from  each  other,  so  as  to  leave  an 
interval,  the  general  ventricular  space,  across  which  some  slighter 
connecting  portions  of  nervous  substance  pass  from  one  hemisphere 
to  another. 

Again,  as  seen  on  a transverse  vertical  section  of  the  cerebrum,  fig. 
343,  the  peduncles,  b,  g,  diverge  as  they  ascend  towards  the  hemi- 
spheres, and  pass  on  each  side  through  two  large  masses  of  gray 
matter,  sometimes  called  ganglia  of  the  brain, — at  first  through  the 
thalamus  opticus,  I,  and  afterwards  through  a much  larger  mass, 
named  corpus  striatum,  k.  These  two  masses  of  gray  matter  project 
somewhat,  as  smooth  convex  eminences,  on  the  upper  and  inner 


INTERNAL  PARTS  OF  CEREBRUM. 


211 


surface  of  the  diverging  fibres  of  the  peduncles.  Immediately  above 
the  thalami  and  corpora  striata,  the  hemispheres  are  connected  together 
across  the  median  plane  by  the  corpus  callosum,  q ; and  it  is  between 
the  under  surface  of  the  latter,  s,  and  the  upper  surface  of  the  emi- 
nences mentioned  and  the  interpeduncular  structures,  that  the  general 
ventricular  space  is  situated  in  the  interior  of  the  cerebrum.  The 
upper  part  of  this  space  is  again  divided  by  a median  vertical  partition, 
so  as  to  form  the  two  lateral  ventricles : below  this,  it  forms  a single 
cavity,  named  the  third  or  middle  ventricle,  which  communicates  with 
both  the  lateral  ventricles  above,  and,  below,  with  the  ventricle  of  the 
cerebellum  or  fourth  ventricle.  The  median  vertical  partition,  which 
separates  the  lateral  ventricles  from  each  other,  consists  at  one  part 
(septum  lucidum)  of  two  layers,  between  which  is  contained  the  fifth 
and  remaining  ventricle  of  the  brain. 

The  anatomy  of  these  parts  is  conveniently  studied  by  removing 
successive  portions  of  the  hemispheres  by  horizontal  sections,  begin- 
ning from  above. 

The  first  horizontal  section,  to  be  made  about  half  an  inch  above 
the  corpus  callosum,  displays  the  internal  white  matter  of  each  hemi- 
sphere, speckled  with  red  spots  where  its  blood-vessels  have  been 
divided,  and  surrounded  on  all  sides  by  the  gray  matter,  which  is  seen 
to  follow  accurately  the  convoluted  surface,  and  to  be  of  nearly  equal 
thickness  at  all  points.  This  Vv'hite  central  mass  in  each  hemisphere 
was  named  by  Vicq-d’Azyr  the  lesser  oval  centre  (centrum  ovale 
minus).  On  separating  the  remaining  portions  of  the  two  hemispheres 
from  each  other,  it  is  seen  that  they  overlap  the  corpus  callosum  for 
some  distance  at  each  side.  These  projecting  margins  of  the  hemi- 
spheres, w’hich  are,  in  fact,  part  of  the  gyrus  fornicatus,  on  each  side, 
have  been  named  labia  cerebri,  and  the  spaces  covered  in  by  them, 
the  ventricles  of  the  coi'pus  callosum, — though  these  parts  do  not  seem 
to  need  any  special  designation. 

The  hemispheres  being  in  the  next  place  sliced  off  down  to  the  level 
of  the  corpus  callosum,  the  white  substance  of  that^art  is  seen  to  be 
continuous  with  the  internal  medullary  matter  of  both  hemispheres  : 
and  the  large  white  medullary  mass  thus  displayed,  surrounded  by  the 
border  of  cortical  substance,  constitutes  what  is  generally  described 
as  the  centrum  ovale  of  Vieussens. 

It  may  here  be  stated  generally,  that  the  gray  matter  of  some  of  the 
convolutions  in  the  posterior  part  of  the  brain,  consists,  as  seen  on  a 
section,  of  an  external  darker  and  an  internal  light  layer,  fig.  333,  r. 
This  appearance  is  usually  well  marked  on  the  inner  or  flat  surface  of 
the  posterior  lobe.  Some  authors  (Baillarger,  Remak,  and  Foville) 
describe  several  alternate  white  and  gray  layers  in  the  cortical  sub- 
stance of  many  of  the  convolutions. 

The  corpus  callosum  (seen  in  section,  fig.  332,  a,  b,)  which  is  now 
supposed  to  be  completely  exposed  above,  also  named  the  beam  of  the 
brain  (trabs  cerebri)  and  great  commissure,  is  the  cross  portion  of 
white  substance  which  lies  between  the  hemispheres  at  the  bottom  of 
the  longitudinal  fissure.  It  is  three  inches  and  upwards  in  length,  and 
extends  further  forwards  than  backwards,  reaching  to  about  an  inch 


212 


INTERNAL  PARTS  OF  CEREBRUM. 


and  a half  of  the  anterior,  and  not  quite  two  inches  and  a half  of  the 
posterior  extremity  of  the  cerebrum.  It  is  about  eight  or  ten  lines  in 
width  behind,  and  somewhat  narrower  in  front.  Its  thickness,  which 
can  only  be  seen  on  a vertical  section,  fig.  332,  is  greater  at  the  ends 
than  in  the  middle,  and  is  greatest  behind,  where  it  amounts  to  three 
lines.  In  form  it  is  somewhat  arched  from  before  backwards.  Its 
upper  surface,  (partly  seen  at  fig.  333,  d,)  is  deeply  marked  by  trans- 
verse fasciculi,  which  indicate  the  cross  direction  of  the  greater  num- 
ber of  its  fibres.  Along  the  middle  line  is  seen  a line  or  mark,  called 
the  raphe  or  seam,  which  is  bounded  laterally  by  two  white  tracts, 
placed  close  to  each  other,  named  strioe  longiiudinales,  or  nerves  of 
Lancisi.  On  each  side,  near  the  margin  of  the  gyrus  fornicatus,  are 
seen  other  longitudinal  lines  (striae  longitud.  laterales)  which  are  occa- 
sioned by  a few  scanty  white  fibres  having  that  direction.  The  arte- 
ries of  the  corpus  callosum  run  along  its  upper  surface,  and  the  edge 
of  the  falx  cerebri  approaches  closely  to  it  behind,  though  not  in  front. 

At  the  two  sides,  the  corpus  callosum  is  connected  with  the  white 
substance  of  the  hemispheres  by  an  extension  of  its  fibres  into  them. 

In  front  it  is  reflected  downwards  and  backwards,  between  the  an- 
terior lobes,  towards  the  base  of  the  brain,  forming  a bend  named  the 

Fig.  332. 


A vertical  section  in  the  median  plane,  of  the  cerebrum,  cerebellum,  pons,  and  medulla  ob- 
longata— the  parts  being  all  represented  in  tbeir  natural  position.  (After  Sosmmerring.)  a.  An- 
terior, and  b.  Posterior  extremity  of  corpus  callosum,  which  is  seen  in  section.  d,c,e.  Thi«l  ven- 
tricle. c.  Soft  commissure,  d,  e.  Thalamus  opticus,  forming  side  of  third  ventricle,  f.  Fornix, 
united  behind  to  corpus  callosum.  6,  g.  Anterior  pillars  of  fornix.  Between  g and  h,  anterior 
commissure.  Behind  h,  lamina  cinerea.  It  k'  h".  Convolution  of  corpus  callosum  or  gyrtts  forni- 
catus. i.  Infundibulum.  I:.  Corpora  quadrigemina,  seen  in  section,  k to  1.  Valve  of  Vieussens. 
1.  Section  of  cerebellum,  showing  white  and  gray  matter — appearance  named  arbor  vitoe.  m. 
Notch  of  cerebellum,  n.  Corpus  albicans  of  right  side.  o.  Pons  Varolii  (section),  p.  Pituitary 
body.  r.  Choroid  plexus,  .s.  Septum  lucidum.  t.  Cerebral  peduncle  of  right  side  in  section,  u. 
Pineal  gland,  ti.  Cavity  of  fourth  ventricle.  <i.  to  u.  Iter  a tertio  ad  quartum  venlriculum,  or 
aqueduct  of  Sylvius,  x x'  x".  Marginal  convolution  of  the  longitudinal  fissure,  y.  Posterior  lobe 
of  cerebrum.  2.  Opening  leading  into  fourth  ventricle.  1.  Olfactory  nerve.  3.  Optic  nerve 
divided  through  optic  commissure.  3.  Third  nerve,  or  motor  oculi. 


INTERNAL  PARTS  OF  CEREBRUM. 


213 


knee  (genu),  a.  The  inferior  or  reflected  portion,  which  is  named  the 
beak  (rostrum),  becomes  gradually  narrower  as  it  descends  (behind 
h).  It  is  attached  at  each  side  to  the  anterior  cerebral  lobe,  and  is 
connected  at  its  point  by  means  of  the  lamina  cinerea  with  the  optic 
commissure.  It  also  gives  oflf  the  two  bands  of  white  substance, 
already  noticed  as  the  peduncles  of  the  corpus  callosum,  which, 
diverging  from  one  another,  run  backwards  across  the  anterior  perfo- 
rated space  on  each  side  to  the  enti'ance  of  the  Sylvian  fissure. 

Behind,  the  corpus  callosum  terminates  in  a free  thickened  border 
(bourrekt),  the  under  surface  of  w'hich  is  also  free  for  a little  distance 
forwards. 

The  under  surface  of  the  corpus  callosum  is  connected  behind  with 
the  fornix,  /,  a structure  to  be  presently  described,  and  in  the  rest  of 
its  length  with  the  septum  lucidum,  s,  the  vertical  partition  between 
the  lateral  ventricles. 

Although  it  presents  a few  longitudinal  white  fibres  on  its  surface, 
the  corpus  callosum  consists  almost  entirely  of  fibres  having  a trans- 
verse course  towards  each  side,  and  spreading  in  all  directions  into 
the  substance  of  the  two  hemispheres.  Only  the  median  portion  of 
these  fibres  between  the  hemispheres  is  seen  without  dissection.  As 
the  transverse  fibres  from  the  anterior  and  posterior  lobes  of  the  cere- 
brum are  necessarily  aggregated  in  large  numbers  near  the  corre- 
sponding ends  of  the  corpus  callosum,  its  relative  thickness  at  those 
points,  in  comparison  wdtb  the  rest  of  its  extent,  is  accounted  for ; and 
since  the  posterior  lobe  reaches  further  beyond  the  corpus  callosum 
than  the  anterior,  the  greater  thickness  behind  is  also  explained. 

By  dividing  the  fibres  of  the  corpus  callosum  in  a longitudinal  direc- 
tion at  a short  distance  on  each  side  of  the  middle  line,  and  about 
midway  between  the  two  ends  of  the  hemispheres,  an  opening  is  made 
into  the  right  and  left  lateral  ventricles  of  the  brain.  These  ventricles 
form  part  of  the  general  ventricular  space  within  the  cerebrum  ; they 
are  serous  cavities,  and  are  lined  by  a delicate  epitheliated  membrane, 
which  is  provided  wdth  cilia.  In  the  natural  state,  their  walls  are 
moistened  internally  with  a serous  fluid,  which  sometimes  exists  in 
considerable  quantity,  even  in  a heahhy  brain. 

Henle  states  that  the  lining  membrane  of  the  ventricles  consists  of  epithelium 
only,  which  lies  immediately  on  the  nervous  matter.  We  have  once  observed  an 
appearance  unfavourable  to  this  view.  In  the  instance  in  question,  the  membrane 
over  the  surface  of  the  corpora  striata  and  adjacent  parts  was  raised  into  small 
vesicular  elevations  by  a clear  fluid, — an  appearance  which  was  most  probably 
due  to  a plexus  of  lymphatic  vessels  distended  with  lymph. 

The  part  of  the  lateral  ventricles  which  is  laid  open  by  the  steps 
already  indicated,  is  named  the  centre  or  body ; from  this  point  each 
ventricle  is  extended  in  three  directions,  forming  so  many  prolonga- 
tions named  horns  (cornua),  which  may  be  displayed  by  carefully 
slitting  up  and  removing  the  white  medullary  substance  of  the  hemi- 
sphere which  covers  them  in.  From  the  direction  taken  by  these 
cornua,  they  are  named  the  anterior,  posterior,  and  middle  or  de- 
scending cornua  ; and  the  lateral  ventricles  themselves  are  named  ven- 
triculi  tricornes.  The  anterior  cornu,  fig.  333,  g,  passes  forwards  and 
outwards  in  the  substance  of  the  anterior  lobe ; the  posterior  cornu,  h. 


214 


INTERNAL  PARTS  OF  CEREBRUM. 


backwards,  outwards,  and  inwards  in  the  posterior  lobe;  and  the  de- 
scending cornu,  q,  which  traverses  the  middle  lobe,  passes  at  first 
backwards,  outwards,  and  downwards,  and  then  changing  its  course. 

Fig.  333. 


Section  of  cerebrum,  displaying  the  lateral  ventricles.  On  the  right  side  the  descending  cornu 
is  laid  open,  o,  i.  Parts  of  great  longitudinal  fissure,  c.  Section  of  front  of  corpus  callosum,  d. 
Part  of  posterior  end  of  the  same.  f.  The  body  of  the  fornix,  e.  The  left  choroid  plexus,  g. 
Anterior  cornu, /i,  posterior,  and  q,  descending  cornu  of  the  lateral  ventricle,  k k.  Corpora  stri- 
ata. f 1.  Optic  thalami.  ?i  n.  Right  and  left  hippocampus  minor,  o.  Posterior  pillar  of  fornix, 
becoming  continued  as  the  corpus  fimbriatum  v.  q.  Cornu  ammonis,  or  Pes  hippocampi,  r. 
Shows  alternate  gray  and  white  layers  in  cortical  substance,  s s.  Right  and  left  tasnia  semicir- 
cularis.  V.  Corpus  fimbriatum.  y.  Eminentia  collateralis. 

runs  forwards  and  inwards  nearly  to  the  point  of  the  middle  lobe. 
The  posterior  cornu,  also  named  the  digital  cavity,  is  very  variable  in 
extent,  even  in  the  two  sides  of  the  same  brain. 

The  parts  forming  the  boundaries  of  the  lateral  ventricles,  and  those 
seen  within  them,  may  be  first  enumerated,  and  will  afterwards  be 
described  in  detail. 

The  body  of  this  ventricle  is  covered  in  by  the  corpus  callosum, 
which  is  therefore  said  to  form  its  roof  On  the  inner  side  in  the 
median  plane  is  a vertical  partition,  the  septum  lucidum,  fig.  332,  s, 
which  descends  between  the  two  lateral  ventricles,  from  the  under 
side  of  the  corpus  callosum,  to  the  fornix.  The  fornix,  f,  itself,  at- 
tached to  the  lower  edge  of  the  septum,  is  partly  seen  in  the  floor  of 
this  part  of  the  ventricle.  Appearing  from  below  the  outer  margin  of 
the  fornix  is  seen  a red  vascular  fringe,  the  choroid  plexus,  e,  next  to 
that  a portion  of  the  upper  surface  of  the  thalamus  opticus,  1.  Beyond 
the  thalamus  is  the  corpus  striatum,  k,  and  between  the  two  last- 
named  parts,  is  a narrow  tape-like  band,  tcenia  semicircularis,  r.  On 
the  outer  side  of  the  corpus  striatum  we  arrive  again  at  the  under  sur- 
face of  the  corpus  callosum. 


INTERNAL  PARTS  OF  CEREBRUM. 


215 


The  anterior  cornu  is  also  covered  in  by  the  corpus  callosum ; it 
turns  round  the  anterior  free  extremity  of  the  corpus  striatum,  de- 
scending as  it  proceeds,  and  is  bounded  behind  by  that  body,  and  in 
front  by  the  reflected  part  of  the  corpus  callosum. 

The  middle  or  descending  cornu  turns  round  the  back  part  of  the 
optic  thalamus  which  appears  in  its  cavity,  and  forms  its  anterior 
boundary.  It  is  covered  in  by  the  thalamus,  and  by  the  medullary 
substance  of  the  middle  lobe.  The  principal  object  seen  upon  its 
floor  is  a long  curved  eminence,  which  follows  the  direction  of  the 
cornu  towards  its  anterior  extremity,  and  is  notched,  or  indented  on 
its  surface ; this  is  the  hippocampus  major,  q.  Along  the  inner  edge 
of  this  eminence  is  seen  a narrow  white  band,  named  corpus  Jim bria- 
tum,  V,  which  is  prolonged  from  the  fornix ; to  the  inner  side  of  that 
is  a part  of  the  choroid  plexus,  e,  and  next  to  that  the  back  of  the 
optic  thalamus. 

The  posterior  cornu  seems,  as  it  were,  scooped  out  of  the  substance 
of  the  posterior  lobe.  The  choroid  plexus  does  not  enter  it.  On  its 
floor  is  seen  a longitudinal  ridge,  named  hippocampus  minor,  or  ergot, 
n ; and  at  the  junction  of  the  posterior  with  the  descending  cornu, 
between  the  hippocampus  major  and  minor,  is  a smooth  eminence, 
which  varies  much  in  size,  named  eminentia  collateralis,  y. 

The  septum  lucidum,  is  a thin  translucent  partition,  (fig.  332,  s,)  placed 
between  the  two  lateral  ventricles.  It  extends  vertically  between  the 
corpus  callosum  above,  and  the  anterior  part  of  the  fornix  below ; and 
as  the  latter  sinks  down  in  front  away  from  the  corpus  callosum,  the 
septum  is  somewhat  triangular  in  form,  being  deep  before  and  narrow 
behind.  The  septum  lucidum  is  attached  above,  in  front,  and  for  a 
certain  space  below,  to  the  corpus  callosum,  fitting  in,  as  it  were,  into 
its  anterior  reflected  portion.  Below  and  further  back  it  is  attached 
to  the  fornix. 

This  vertical  septum  is  double,  being  composed  of  two  perfectly 
distinct  laminae,  having  an  interval  between  them,  which  contains  fluid 
and  is  lined  by  an  epitheliated  membrane.  This  is  the  fifth  ventricle, 
ventricle  of  the  septum,  or  Sylvian  ventricle.  It  may  be  laid  open  by 
cutting  through  the  corpus  callosum,  and  detaching  it  for  a certain 
distance  from  the  upper  border  of  the  septum,  (as  in  fig.  333.)  In  the 
human  embryo,  and  also  in  some  animals,  the  cavity  of  this  ventricle 
communicates  with  that  of  the  third  ventricle  in  front  and  below;  but 
in  the  adult  human  brain  it  forms  a separate  and  insulated  cavity. 
Tarin  described  a small  fissure  in  it  between  the  pillars  of  the  fornix; 
but  this  is  unusual.*  In  disease  it  is  often  distended  with  fluid. 

Each  of  the  laminse  of  the  septum  which  form  the  sides  of  the  fifth 
ventricle,  consists  of  an  internal  layer  of  white  substance  and  an  ex- 
ternal layer  of  gray  matter. 

[The  white  fibres  of  the  septum  lucidum  originate  from  the  anterior  lobe  of  the 
cerebrum  and  the  gray  matter  covering  the  external  surface  of  the  septum,  and 
belong  to  the  class  of  antero-posterior  commissures  of  the  cerebrum.  They  may 
be  afterwards  traced  into  the  fornix,  giving  the  latter,  indeed,  a considerable  ac- 
cession.— J.  L.] 

* [A  deep  depression  exists  there,  but  does  not  communicate  with  the  ventricle. — J.  L.] 


216 


INTERNAL  PARTS  OF  CEREBRUM. 


The  fornix  is  a white  longitudinal  band,  extending  along  the  lower 
edge  of  the  septum  lucidura,  and  attached  behind  to  the  under  surface 
of  the  corpus  callosum.  It  appears  in  the  floor  of  both  lateral  ven- 
tricles, fig.  333,/,  0,  and  dips  downwards  at  each  extremity,  fig.  332,/ 
but  rises  in  the  middle  so  as  to  form  a sort  of  vault  or  arch  (fornix),  which 
is  free  on  its  under  surface.  It  may  be  described  as  consisting  of  two 
lateral  halves,  which  are  separated  from  each  other  in  front  and  be- 
hind, but  between  those  points  are  joined  together  in  the  median  plane. 
The  two  parts  in  front  form  the  anterior  pillars  of  the  fornix;  the 
middle  conjoined  part  is  named  the  body;  and  the  hind  parts,  which 
are  again  separated  from  each  other,  form  the  posterior  pillars. 

The  body  of  the  fornix,  fig.  333,  /,  is  triangular  in  shape,  being 
broad  and  flattened  behind,  where  it  is  connected  with  the  under  sur- 
face of  the  corpus  callosum,  and  narrower  in  front  as  it  dips  down  to 
leave  that  body, — the  space  between  them  being  filled  up  by  the  sep- 
tum lucidum.  Its  lateral  edges  are  in  • contact  with  the  choroid 
plexuses,  and  its  under  surface  rests  upon  a membrane,  which  con- 
nects those  two  plexuses  together  (velum  interposilum). 

The  anterior  crura  or  'pillars  of  the  fornix,  figs.  335,  336,/  consist- 
ing entirely  of  white  fibres,  descend  slightly  apart  from  each  other 
through  a quantity  of  gray  matter  on  the  sides  of  the  third  ventricle, 
fig.  345,  t',  as  far  as  the  corpora  albicantia,  n,  where  they  turn  up  and 
enter  the  substance  of  the  corresponding  optic  thalamus,  *.  The  ex- 
ternal or  white  portion  oaf  each  of  the  corpora  albicantia  is  composed 
of  the  fibres  of  the  corresponding  pillar  of  the  fornix,  which  there- 
forms  a twisted  loop.  These  pillars  might  therefore  be  described  as 
commencing  in  the  substance  of  the  thalami,  descending  into  the  cor- 
pora albicantia,  in  which  they  are  twisted  in  the  manner  described, 
then  rising  up  through  the  gray  matter  on  the  sides  of  the  third  ven- 
tricle, becoming  free  above,  and  at  length  joining  together  to  form  the 
body  of  the  fornix.  They  are  connected  with  the  peduncles  of  the 
pineal  gland,  and  with  the  teenia  semicircularis,  as  will  be  afterwards 
described. 

Immediately  behind  the  anterior  pillars  of  the  fornix,  a small  open- 
ing is  seen  on  either  side.  The  two  openings  pass  downwards  and 
backwards  towards  the  middle  line,  and  meeting  below,  lead  into 
the  upper  part  of  the  third  ventricle.  The  passage  thus  formed  is  the 
foramen  of  Monro.  It  is  single  below,  where  it  communicates  with 
the  third  ventricle,  but  divides  above,  somewhat  like  the  letter  Y, 
into  two  branches,  one  to  each  lateral  ventricle.  In  this  way  it  will 
be  seen  that  all  three  ventricles  communicate  with  each  other  at  this 
point. 

The  two  flat  bands  into  which  the  fornix  divides  behind  are  its  pos- 
terior pillars  or  crura,  fig.  333,  o.  Adhering  at  first  to  the  under  sur- 
face of  the  corpus  callosum,  they  pass  backwards  diverging  from  each 
other;  and  then  leaving  the  corpus  callosum,  turn  suddenly  down- 
wards into  the  descending  cornu  of  the  corresponding  lateral  ventricle, 
where  we  shall  presently  follow  them.  On  dividing  the  fornix  across 
in  front,  and  turning  it  back  with  the  corpus  callosum,  so  as  to  expose 
the  under  surface,  a triangular  portion  of  the  laiter,  fig.  335,  e,  is  seen 
between  the  diverging  posterior  crura  of  the  fornix,  marked  with  lines, 


INTERNAL  PARTS  OF  CEREBRUM. 


217 


some  of  which  are  transverse,  but  others  longitudinal  or  oblique.  To 
this  part  the  term  lyra  has  been  applied.* 

In  the  posterior  cornu  of  the  lateral  ventricle,  we  have  to  examine 
the  hifpocampus  minor,  fig.  333,  n,  also  called  the  ergot  or  calcar  avis, 
from  its  resemblance  to  a cock’s  spur.  It  is  a white  eminence  pointed 
at  its  posterior  extremity,  forming  a relief  along  the  inner  side  of  the 
cornu  : beneath  the  white  surface  it  consists  of  gray  matter,  which  is 
part  of  the  cortical  substance  of  the  hemispheres,  corresponding  with 
the  bottom  of  a sulcus  seen  on  the  inner  surface  of  the  posterior  lobe. 

The  hippocampus  major  (pes  hippocampi ; or  cornu  ammonis,  from 
its  resemblance  to  a ram’s  horn)  is  a large  white  eminence,  q,  already 
mentioned  as  lying  along  the  floor  of  the  descending  cornu  of  the 
lateral  ventricle.  Behind  the  pes,  and  between  it  and  the  hippocam- 
pus minor,  is  another  white  eminence,  known  as  the  eminentia  collate- 
ralis,  pes  accessorius,  y,  which  has  a similar  relation  to  a convolution 
as  the  lesser  hippocampus,  and  is  often  as  large  as,  or  larger  than  that 
elevation.  The  hippocampus  major  becomes  enlarged  towards  its 
anterior  and  lower  extremity,  and  is  indented  or  notched  on  its  edge, 
so  as  to  present  some  resemblance  to  the  paw  of  an  animal,  whence, 
no  doubt,  its  name  of  pes  hippocampi. 

The  external  white  substance  of  the  hippocampus  major  is  partly 
derived  from  the  posterior  pillar  of  the  fornix,  which,  as  already  stated, 
enters  the  descending  cornu  of  the  lateral  ventricle.  The  remaining 
part  of  that  pillar  forms  a white  band,  like  a tape,  which  is  attached 
along  the  inner  border  of  the  great  hippocampus,  and  forms  the  tcBuia 
hippocampi,  or  corpus  jimbriatum,  v.  It  reaches  down  to  the  end  of 
the  pes,  but  its  further  connexions  are  not  well  known. 

Along  the  inner  border  of  the  corpus 
fimbriatum,  (which  is  a continuation  of 
the  posterior  pillar  of  the  fornix,)  and 
between  it  and  the  thalamus,  is  the  pro- 
longation of  the  choroid  plexus,  e,  occu- 
pying in  this  situation  a part  of  the 
transverse  fissure,  to  be  presently  de- 
scribed. On  separating  the  corpus  fim- 
briatum from  the  plexus,  and  raising 
the  edge  of  the  former,  we  discover  a 
gray  indented  ridge,  which  runs  paral- 
lel with  it,  but  which,  strictly  speakino;,  o .•  c.i,  u 

\ • 1 I • ^ r-  P Section  of  the  hippocampus  major,  to 

IS  Situated  outside  the  cavity  OI  the  show  the  arrangement  of  iis  gray  and 
cornu.  This  is  the  fascia  dentata,^^.  white  substance,  a.  White  layer  on  us 
_ ’ o surface,  o.  Gray  substance  which  be- 

oo4,  C.  comes  rolled  up.  d.  White  reticulated 


Fig.  334. 


The  Structure  of  the  pes  hippocampi  substance,  on  the  surface  of  gyms  fomi- 
. 1 'll  1 ■ I t r catus.  c.  Fascia  dentata.  e.  Cavity  of 

IS  best  examined  by  making  a cross  sec-  lateral  ventricle. 

tion  through  it.  It  will  then  be  seen 

* The  varying  direction  of  these  lines  has  been  represented  by  Vicq-d’Azyr,  who  attributes 
them  to  the  impression  of  the  vessels  of  the  subjacent  velum  interpositum.  The  term 
corpus  psalloides  given  by  the  early  anatomists  to  the  fornix,  in  consequence  of  its  re- 
semblance to  an  arch  — Galen;  from  or  fornix,  an  arch),  was 

erroneously  interpreted  by  Winslow  and  others,  who  supposed  that  it  meant  something 
which  had  the  appearance  of  a harp  or  similar  stringed  instrument,  and  that  it  was  in- 
tended specially  to  designate  the  part  marked  with  the  linear  impressions  described,  which 
accordingly  was  named  lyra  and  psalterium. 

VOL.  II.  19 


218 


INTERNAL  PARTS  OF  CEREBRUM. 


that  its  surface  is  composed  of  white  substance,  fig.  334,  a,  which  is 
continuous  with  that  of  the  corpus  fimbriatum.  Within,  it  contains  a 
stratum  of  gray  matter,  h,  doubled  on  itself,  and  continued  from  the 
cortical  substance  on  the  adjacent  convolution  of  the  middle  lobe  (part 
of  the  gyrus  fornicatus).  This  gray  layer  accompanied  by  the  thin 
coating  of  white  matter,  d,  already  described  in  this  situation  as  the 
reticulated  white  substance  (see  p.  205),  is  first  bent  inwards,  and  then 
curls  outwards  upon  itself,  so  as  to  terminate  by  a free  indented  edge, 
which  appears  at  the  surface  as  the  fascia  dentata,  c. 

Fig.  335. 


A section  of  the  cerebral  hemispheres,  showing  both  lateral  ventricles,  after  the  fornix  has 
been  divided  and  turned  back,  to  expose  the  velum  interpositum.  c.  The  anterior  portion  of 
corpus  callosum,  cut  across,  e.  The  lyra,  or  under  surface  of  back  of  corpus  callosum.  /.  Ante- 
rior pillars  of  fornix  cut  across.  N.  B.  These  are  represented  of  too  great  size.  g.  Anterior,  A, 
posterior  cornu  of  lateral  ventricle.  A k.  Corpora  striata,  q.  Pes  hippocampi,  r r.  Thalam' 
optici.  s s.  Ttenia  semicircularis.  1 1.  Choroid  plexuses,  v.  Velum  interpositum.  x x.  Poste- 
rior pillars  of  fornix,  y.  Eminentia  collateralis. 

From  what  has  preceded,  it  will  have  been  understood  that  the  for- 
nix is  applied  in  nearly  its  whole  length  to  the  optic  thalamus  of  each 
side — the  body  of  the  fornix,  fig.  333,  f,  resting  on  the  upper  surface 
of  the  thalamus,  I,  and  each  posterior  pillar  being  applied  to  the  pos- 
terior surface  of  that  body  in  the  descending  cornu.  On  separating 
these  two  parts  it  will  be  seen  that  a fissure  exists  between  them.  This 
is  named  the  transverse  fissure  of  the  cerebrum.  Through  it  the  pia 
mater,  from  the  exterior  of  the  brain,  passes  into  the  ventricles  to  form 
the  choroid  plexuses.  This  fissure  runs  downwards  and  forwards  into 
each  descending  cornu;  it  therefore  extends  from  the  point  of  the  de- 
scending cornu  of  one  side  to  that  of  the  other,  reaching  as  far  for- 


INTERNAL  PARTS  OF  CEREBRUM. 


219 


wards  as  the  foramen  of  Monro,  its  extent  corresponding  exactly  with 
that  of  the  choroid  plexuses.  It  is  closed  on  the  inner  side  by  the 
lining  membrane  of  the  lateral  ventricle,  which  is  said  to  pass  from 
the  fornix  to  the  thalamus  over  the  choroid  plexus. 

On  raising  up  the  fornix,  it  will  be  seen  that  it  rests  on  a vascular 
membrane  which  is  interposed  between  it  and  the  parts  beneath.  This 
is  named  the  velum  interpositum  or  tela  choroidea,  fig.  335,  v.  It  con- 
nects the  choroid  plexuses  of  the  two  sides  together,  and  like  them  is 
a prolongation  of  the  pia  mater.  This  last-named  membrane  passes 
from  the  outer  surface  of  the  brain  underneath  the  corpus  callosum 
and  fornix,  and  above  the  corpora  quadrigemina,  the  pineal  gland  and 
the  thalami,  through  the  transverse  fissure  into  the  lateral  ventricle. 
The  membranous  prolongation  thus  formed,  is  of  a triangular  shape : 
the  middle  part  of  it  is  covered  by  the  fornix,  and  constitutes  the  velum 
interpositum,  whilst  the  remainder  projects  at  each  side  of  the  fornix 
into  the  lateral  ventricles,  and  forms  by  its  free  borders  the  right  and 
left  choroid  plexuses. 

The  choroid  plexuses,  fig.  333,  &c.,  e e,  appear  like  two  red  knotted 
fringes,  reaching  from  the  foramen  of  Monro  to  the  point  of  each  de- 
scending cornu.  They  are  represented  as  being  covered  by  a reflec- 
tion of  the  lining  membrane  of  the  ventricle,  which  in  this  way  is  con- 
sidered to  keep  the  choroid  plexuses  outside  the  serous  cavity  of  the 
ventricle,  just  as  the  intestines  are  excluded  from  the  cavity  of  the 
peritoneum  ; but  in  admitting  this  view,  it  must  be  remembered  that 
the  epithelium  changes  its  character  where  it  covers  the  plexuses. 

At  the  foramen  of  Monro,  where  the  middle  and  lateral  ventricles 
communicate,  their  lining  membrane  is  continuous,  and  here  the  two 
choroid  plexuses  are  connected  with  one  another. 

On  raising  the  velum  interpositum,  two  slight  vascular  fringes  are 
seen  running  along  its  under  surface,  and  diverging  from  each  other 
behind.  They  form  the  choroid  plexuses  of  the  third  ventricle. 

The  choroid  plexuses  consist  of  a highly  vascular  villous  membrane. 
The  villi  with  which  they  are  covered  are  again  divided  upon  their 
surfaces  and  at  their  borders  into  smaller  processes,  along  which  fine 
vessels  are  seen  to  run.  They  are  covered  by  a single  layer  of  thick 
epithelium  composed  of  large  roundish  corpuscles,  in  each  of  which  is 
seen,  besides  a distinct  nucleus,  a small  bright  yellow  spot.  The  arte- 
ries of  the  velum  interpositum  and  choroid  plexuses  enter  from  behind 
beneath  the  corpus  callosum,  and  also  at  the  point  of  the  descending 
cornu:  after  ramifying  in  the  plexuses,  they  send  branches  beneath  the 
ventricular  lining  membrane  to  enter  the  substance  of  the  brain.  Veins 
issuing  from  the  cerebral  substance  are  seen  on  the  surface  of  the 
ventricles,  and  for  the  most  part  join  the  veins  of  the  choroid  plexuses. 
The  greater  number  of  these  terminate  in  two  principal  vessels,  named 
the  veins  of  Galen,  which  run  backwards  on  the  velum  interpositum, 
and  passing  out  beneath  the  corpus  callosum  pour  their  blood  into  the 
straight  sinus,  having  generally  first  united  into  a single  trunk. 

The  velum,  having  next  been  removed,  the  optic  thalami  are  brought 
fully  into  view,  and  the  cavity  of  the  third  ventricle,  situated  between 


220 


INTERNAL  PARTS  OF  CEREBRUM. 


them.  In  front  and  to  the  outer  side  of  the  thalami,  as  already  stated, 
are  the  corpora  striata.  These  last  are  two  large  ovoid  masses  of 
gray  matter,  fig.  333,  &c.,  k k,  the  greater  part  of  which  is  embedded 
in  the  middle  of  the  white  substance  of  the  hemisphere  of  the  brain, 
whilst  a part  projects  into  the  fore  part  of  the  body  and  the  anterior 
cornu  of  the  lateral  ventricle.  This  intraventricular  •portion  of  the 
corpus  striatum,  k k,  figs.  335,  336,  is  of  a pyriform  shape,  its  larger 
end  being  turned  forwards,  and  its  narrow  end  being  directed  out- 
wards and  backwards,  so  that  the  optic  thalami  of  the  two  sides  are 
received  between  the  diverging  corpora  striata.  The  surface  of  the 
corpus  striatum  is  composed  of  gray  matter;  it  is  covered  by  the 
lining  membrane  of  the  ventricle,  and  is  crossed  by  veins  of  consider- 
able size.  At  some  depth  from  the  surface,  white  fibres  may  be  seen 
on  cutting  into  it,  which  are  prolonged  from  the  corresponding  cere- 
bral peduncle,  and  give  it  the  streaked  appearance  from  which  it  has 
received  its  name. 

The  extraventricular  portion  of  the  corpora  striata  will  be  after- 
wards described. 

Along  the  inner  border  of  each  corpus  striatum,  and  in  a depression 
between  it  and  the  optic  thalamus,  is  seen  a narrow,  whitish,  semi- 
transparent band,  named  tcenia  semicircularis,  fig.  333,  &c.,  s s,  which 
continues  backwards  into  the  descending  cornu  of  the  ventricle, 
where  its  connexions  cannot  be  assigned  with  precision.  In  front  it 
reaches  the  corresponding  anterior  pillar  of  the  fornix,  and  descends 
in  connexion  with  that  cord  of  white  substance.  It  is  more  transpa- 
rent and  firm  on  the  surface,  especially  at  its  fore  part : and  this  super- 
ficial stratum  has  been  named  stria  cornea.  The  trenia  consists  of 
longitudinal  white  fibres,  the  deepest  of  which  running  between  the 
corpus  striatum  .and  the  thalamus,  were  named  by  Vieussens  centrum 
geminum  semicirculare.  Beneath  it  are  one  or  two  large  veins,  which 
receive  those  upon  the  surface  of  the  corpus  striatum,  and  end  in  the 
veins  of  the  choroid  plexuses. 

The  thalami  optici,  figs.  333  to  336,  I /,  (posterior  ganglia  of  the 
brain,)  are  of  an  oval  shape,  and  rest  on  the  corresponding  cerebral 
crura,  which  they  in  a manner  embrace.  On  the  outer  side  each 
thalamus  is  bounded  by  the  corpus  striatum  and  taenia  semicircularis, 
and  is  then  continuous  with  the  medullary  substance  of  the  hemi- 
sphere. Its  upper  surface  is  free  and  prominent  and  is  partly  seen  in 
the  lateral  ventricle,  k,  and  partly  covered  by  the  fornix.  The  poste- 
rior surface,  which  is  also  free,  projects  into  the  descending  cornu  of 
the  lateral  ventricle.  The  inner  sides  of  the  two  thalami  are  turned 
towards  each  other,  and  form  the  lateral  boundaries  of  the  third  ventricle, 
across  which,  however,  they  are  connected  by  a gray  mass  of  nervous 
substance,  named  the  soft  commissure.  Near  the  fore  part  of  each 
thalamus  is  a small  elevation  on  its  upper  surface,  named  its  anterior 
tubercle,  fig.  336,  *.  The  optic  thalami  are  white  on  the  surface,  and 
consist  of  several  layers  of  white  fibres  intermixed  with  gray  matter. 

The  third  ventricle,  fig.  336,  z to  s,  is  a narrow  longitudinal  fissure 
or  cleft  placed  between  the  optic  thalami,  which  bound  it  on  its  two 


INTERNAL  PARTS  OF  CEREBRUM. 


221 


sides.  It  is  covered  above  by  the  velum  interpositum  and  the  fornix. 
Beneath,  its  floor  is  formed  by  the  following  parts,  which  have  been 
already  described,  as  seen  on  the  base  of  the  cerebrum,  viz.,  com- 
mencing from  behind,  the  posterior  perforated  space,  the  corpora 
albicantia,  the  tuber  cinereum  and  infundibulum,  and  the  lamina  cine- 
rea,  which  also  serves  to  close  it  in  front,  as  high  as  the  anterior  com- 
missure. Passing  across  the  cavity  of  the  third  ventricle  are  seen 


Fig.  336. 


Section  of  the  cerebrum,  displaying  the  surfaces  of  the  corpora  striata,  and  optic  thalarai,  the 
cavity  of  the  third  ventricle,  and  the  upper  surface  of  the  cerebellum, — a e.  Corpora  quadrige- 
mina, — a testis,  e nates.  6.  Soft  commissure,  c.  Corpus  callosum,  f.  Anterior  pillars  of  fornix. 
g.  Anterior  cornu  of  lateral  ventricle,  h k.  Corpora  striata.  1 1.  Optic  thalami.  * Anterior 
tubercle  of  the  left  thalamus,  z to  s.  Third  ventricle.  In  front  of  z,  anterior  commissure,  b. 
Soft  commissure,  s.  Posterior  commissure,  p.  Pineal  gland  with  its  peduncles,  n n.  Proces- 
sus a cerebello  ad  testes,  m m.  Hemispheres  of  the  cerebellum,  h.  Superior  vermiform  process, 
t.  Notch  behind  the  cerebellum. 

three  commissures,  named  from  their  position,  anterior,  middle,  and 
posterior. 

The  middle  or  soft  commissure,  h,  (com.  mollis,)  is  composed  almost 
entirely  of  gray  matter,  and  connects  the  two  thalami.  It  is  some- 
times, though  very  rarely,  wanting ; but  it  is  more  frequently  torn 
across  in  examining  the  brain. 

The  anterior  commissure,  in  front  of  z,  is  a round  bundle  of  white 
fibres,  placed  immediately  in  front  of  the  anterior  pillars  of  the  fornix, 
and  crosses  between  the  corpora  striata.  It  marks  the  anterior 
boundary  of  the  ventricle ; its  fibres  extend  laterally  through  the  cor- 
pora striata,  a long  distance  into  the  substance  of  the  cerebral  hemi- 
spheres. 


19* 


222 


INTERNAL  PARTS  OF  CEREBRUM. 


Tlie  posterior  compiissure,  s,  also  white,  is  placed  across  the  back 
part  of  the  ventricle,  immediately  before  and  below  the  pineal  gland. 
It  is  smaller  than  the  anterior  commissure,  and  has  the  form  of  a flat- 
tened band.  It  passes  into  the  thalami  on  each  side,  but  does  not 
extend  so  far  into  the  substance  of  the  brain  as  the  anterior  com- 
missure. 

The  following  apertures  lead  from  or  into  the  third  ventricle: 

Above  and  before  is  the  foramen  of  Monro,  by  which  the  third 
communicates  with  the  two  lateral  ventricles. 

Behind,  is  an  opening  leading  into  the  iter  a tertlo  ad  quartum  ven- 
tricuhim,  or  aqueduct  of  Sylvius,  fig.  332,  d,  v,  which  passing  down 
below  the  posterior  commissure,  and  the  corpora  quadrigemina,  con- 
ducts into  the  fourth  ventricle. 

In  the  floor  of  the  third  ventricle  is  a deep  pit,  corresponding  with 
the  infundibulum,  and  generally  named  iter  ad  infundibulum,  but  there 
is  no  outlet  at  this  part. 

The  lining  membrane  of  the  lateral  ventricles  is  continued  down 
through  the  foramen  of  Monro,  and  lines  the  third  ventricle,  whence  it 
extends  along  the  Sylvian  aqueduct  into  the  fourth  ventricle.  Bichat 
conceived  that  this  membrane  was  continuous  with  the  arachnoid 
membrane  on  the  exterior  of  the  brain,  and  he  therefore  named  it  the 
internal  arachnoid.  He  supposed  that  the  external  arachnoid  mem- 
brane entered  the  third  ventricle  in  the  form  of  a tubular  process, 
which  passed  beneath  the  posterior  end  of  the  corpus  callosum  and 
fornix,  above  the  pineal  gland  and  through  the  velum  interpositum, 
and  thus  opened  into  the  upper  and  back  part  of  the  third  ventricle. 
The  existence  of  this  canal,  named  the  canal  of  Bichat,  is  doubtful.  It 
is  certainly  not  constant. 

Pineal  gland  and  corpora  quadrigemina. — Behind  the  third  ventricle, 
and  in  front  of  the  cerebellum,  are  certain  eminences,  which  may  be 
reached  from  the  surface  of  the  brain.  These  are  the  corpora  quad- 
rigemina, and  above  them  is  the  pineal  gland. 

The  pineal  gland,  fig.  332,  u,  fig.  336,  p.  (conarium,)  so  named  from 
its  shape  (pinus,  conus,  the  fruit  of  the  fir,)  is  a small  reddish  body, 
which  is  placed  beneath  the  back  part  of  the  corpus  callosum,  and 
rests  upon  the  anterior  pair  of  the  corpora  quadrigemina.  It  is  very 
firmly  attached  to  the  under  surface  of  the  velum  interpositum,  so 
that  it  is  liable  to  be  torn  away  from  the  brain  in  removing  that  mem- 
brane. It  is  about  three  lines  in  length,  and  its  broad  part  or  base  is 
turned  forwards,  and  is  connected  with  the  rest  of  the  cerebrum  by 
white  substance.  This  white  substance  is  principally  collected  into 
two  small  rounded  bundles,  named  peduncles  of  the  pineal  gland, 
which  pass  forwards  upon  the  optic  thalami,  to  which  they  are  at- 
tached along  the  upper  limit  of  the  third  ventricle,  and  may  be  traced 
in  that  direction  as  far  as  the  anterior  pillars  of  the  fornix,  in  con- 
junction with  which  they  descend,  fig.  336.  These  peduncles  are 
connected  with  each  other  behind.  The  base  of  the  pineal  gland  is 
also  connected  by  a transverse  lamella  of  white  substance  with  the 
back  of  the  posterior  commissure.  Some  anatomists  have  described 


INTERNAL  PARTS  OF  CEREBRUM. 


223 


two  inferior  peduncles,  which  descend  upon  the  inner  surface  of  the 
thalami. 

The  pineal  'gland  is  very  vascular.  It  is  hollowed  out  into  two  or 
more  cells,  which,  sometimes  at  least,  open  anteriorly  into  the  ventri- 
cle, and  almost  always  contain,  besides  a viscid  fluid,  a quantity  of 
gritty  matter,  named  acervulus  cerebri.  This  consists  of  microscopic 
round  particles,  aggregated  into  small  compound  masses,  w'hich  are 
again  collected  into  larger  groups.  It  is  composed  of  earthy  salts 
combined  with  animal  matter;  viz.,  phosphate  and  carbonate  of  lime, 
with  a little  phosphate  of  magnesia  and  ammonia  (Stromeyer).  It  is 
found  at  all  ages,  frequently  in  young  children,  and  sometimes  even  in 
the  foetus.  It  cannot,  therefore,  be  regarded  as  the  product  of  disease. 
This  sabulous  matter  is  frequently  found  on  the  outside  of  the  pineal 
body,  or  even  deposited  upon  its  peduncles. 

The  corpora  or  tubercula  quadrigemina  are  four  rounded  emi- 
nences, fig.  336,  a e,  separated  by  a crucial  depression,  placed  two 
on  each  side  of  the  middle  line,  one  before  another.  They  are  con- 
nected with  the  back  of  the  optic  thalami,  and  with  the  cerebral 
peduncles  at  either  side;  and  they  are  placed  above  the  passage  lead- 
ing from  the  third  to  the  fourth  ventricle. 

The  upper  or  anterior  tubercles,  fig.  330,  a a,  are  somewhat  larger 
and  darker  in  colour  than  the  posterior,  b b.  In  the  adult,  both  pairs 
are  solid,  and  are  composed  of  w'hite  substance  outside  containing 
gray  matter  within. 

They  receive  bands  of  white  fibres  from  below,  the  chief  of  which 
are  derived  from  a fasciculus  named  the  fillet.  A white  cord  also 
passes  up  on  each  side  from  the  cerebellum  to  the  corpora  quadrige- 
mina, and  is  continued  onwards  to  the  thalami:  these  two  white  cords 
are  the  processus  a cerebello  ad  testes,  or  superior  peduncle  of  the 
cerebellum,  fig.  330,  f,  fig.  336,  n n.  At  each  side,  the  corpora  quad- 
rigemina send  off  two  white  tracts,  which  pass  to  the  thalami  and  to' 
thb  commencements  of  the  optic  nerves.  These  tracts  are  prominent 
on  the  surface,  and  are  sometimes  named  brachia. 

In  the  human  brain  these  quadrigeminal  bodies  are  small  in  com- 
parison w’ith  their  size  in  the  series  of  animals.  In  ruminant,  soliped, 
and  rodent  animals,  the  anterior  tubercles  are  much  larger  than  the  pos- 
terior, as  may  be  seen  in  the  sheep,  horse,  and  rabbit ; and  hence  have 
been  applied  the  names  nates  to  the  anterior  and  testes  to  the  posterior 
tubercles.  In  the  brains  of  carnivora,  the  posterior  tubercles  are 
rather  the  larger. 

In  the  foetus,  this  part  of  the  brain  appears  very  early,  and  then 
forms  a large  proportion  of  the  cerebral  mass.  The  eminences  are  at 
first  single  on  each  side  and  hollow.  They  are  constant  in  the  brains 
of  all  vertebrate  animals,  but  in  fishes,  reptiles,  and  birds,  they  are 
only  two  in  number,  and  hollow  : in  marsupialia  and  monotremata, 
they  are  also  two  in  number,  but  are  solid. 

To  the  outer  side  of  the  corpora  quadrigemina,  and  on  the  under  and 
back  part  of  each  optic  thalamus,  are  found  two  small  oblong  and  flat- 
tened eminences,  connected  with  the  posterior  extremity  of  the  optic 
tract.  These  optic  tracts,  which  we  have  already  seen  on  the  base  of 


224 


THE  CEREBELLUM. 


the  cerebrum,  attached  to  and  embracing  the  under  side  of  the  corre- 
sponding peduncles, 'may  be  traced  back  to  the  thalami.  Each  tract 
becomes  flattened  and  broader  as  it  approaches  the  thalamus,  and 
makes  a bend  as  it  turns  round  the  peduncle  to  reach  the  back  part  of 
that  body.  Near  this  bend,  which  is  named  the  knee  (genu),  are 
placed  the  two  small  eminences  just  spoken  of.  They  are  two  little 
masses  ot  gray  matter,  about  the  size  and  shape  of  coffee-beans,  placed 
one  on  the  outer  and  one  on  the  inner  side  of  the  genu  of  the  optic 
tract,  and  hence  are  named  xes\>ec\.\\a\y  corpus  geniculatum,  externum 
and  internum.  They  send  fibres  into  the  optic  tract,  and  also  into  the 
thalamus  of  the  same  side. 

The  fibres  of  these  tracts  are  therefore  derived  from  three  sources, 
viz.,  the  thalamus,  the  tubercula  quadrigemina,  and  the  corpora 
geniculala. 

Extending  downwards  and  somewhat  outwards  from  the  corpora 
quadrigemina  to  the  fore  part  of  the  cerebellum,  and  connecting  the 
latter  with  the  cerebrum,  are  two  large  white  cords,  the  processus  a 
cerebello  ad  testes,  fig.  336,  n,  n,  already  alluded  to.  Between  them 
is  stretched  a thin  semi-transparent  layer  of  nervous  matter,  which 
lies  over  the  passage  from  the  third  to  the  fourth  ventricle,  and,  lower 
down,  covers  in  a part  of  the  fourth  ventricle  itself.  This  is  the  valve 
of  Vieussens,  between  n n (velum  medullare  anterius).  It  is  narrow 
above,  where  it  is  connected  with  the  quadrigeminal  bodies,  and 
broader  below,  where  it  is  continuous  with  the  median  portion  of  the 
cerebellum.  From  its  attachment  at  the  sides  to  the  processus  ad 
testes,  these  latter  have  been  described  as  the  pillars  of  the  valve. 

The  upper  portion  of  the  valve  is  composed  of  medullary  substance, 
but  a few  transverse  ridges  of  gray  matter  extend  upon  its  lower  half, 
as  if  they  were  prolonged  from  the  gray  lamellae  of  the  cerebellum, 
with  which  it  is  there  continuous,  From  between  the  posterior  quad- 
rigeminal tubercles  a slight  median  ridge,  x\d.raQ  frcenulum,  descends  a 
little  way  upon  the  velum  ; and  on  each  side  of  this  the  commencing 
transverse  fibres  of  the  fourth  pair  or  pathetic  nerves  may  be  seen. 

The  valve  of  Vieussens  is  overlapped  and  concealed  by  the  adjacent 
folia  of  the  cerebellum,  which  must  be  drawn  back  in  order  to  bring  it 
into  view. 

THE  CEREBELLUM. 

The  cerebellum,  little  brain,  or  after  brain,  consists  of  a body  and 
three  pairs  of  crura  ox  peduncles,  by  which  it  is  connected  with  the 
rest  of  the  encephalon.  They  are  named  superior,  middle,  and  infe- 
rior peduncles,  and  have  all  been  incidentally  mentioned. 

The  superior  peduncles  connect  the  cerebellum  with  the  cerebrum 
(crura  ad  cerebrum).  They  are  the  parts  already  described  under 
the  name  of  the  processus  ad  testes. 

Hhe  in  ferior  peduncles  (processus  a cerebello  ad  medullam;  crura 
ad  medullam)  pass  downwards  to  the  back  part  of  the  medulla  oblon- 
gata, and  correspond  with  the  restiform  bodies. 

The  middle  peduncles  (crura  ad  pontem)  pass  from  the  middle  of 
the  cerebellum  around  the  outer  side  of  the  crux’a  of  the  cerebrum,  and 


THE  CEREBELLUM. 


225 


meet  in  front  in  the  pons  Varolii,  constituting  its  transverse  fibres. 
They  connect  the  two  halves  of  the  cerebellum  together  below. 

All  these  peduncles  consist  of  white  fibres  only ; and  they  pass  into 
the  interior  of  the  cerebellum  at  its  fore  part.  Their  connexions  within 
that  organ  will  be  afterwards  described. 

The  body  of  the  cerebellum  being  covered  with  cortical  substance, 
is  of  a gray  colour  externally,  but  is  rather  darker  on  the  surface  than 
the  cerebrum.  Its  greatest  diameter  is  transverse ; it  is  about  three 
and  a half  or  four  inches  wide,  about  two  or  two  and.  a half  from  be- 
fore backwards,  and  about  two  inches  deep  in  the  thickest  part,  but  is 
much  thinner  all  around  its  outer  border. 

It  consists  of  two  lateral  hemispheres  joined  together  by  a median 
portion  called  the  worm,  or  vermiform  process,  which  in  birds  and  in 
some  animals  still  lower  in  the  scale  is  the  only  part  existing. 

The  hemispheres  are  separated  behind  by  a deep  notch,  figs.  336, 
337,  i,  so  that  the  outline  of  the  two,  as  seen  from  above,  resembles  a 


very  wide-shaped  heart  as  drawn  on  playing  cards,  the  notch  being 
directed  backwards.  On  the  upper  surface,  the  median  portion  or 
superior  vermiform  process,  fig.  336,  h,  though  slightly  elevated,  is 
scarcely  marked  off  from  the  hemispheres,  so  that  the  general  surface 
of  the  organ,  which  is  here  inclined  on  either  side,  is  uninterrupted. 
Below,  the  hemispheres  are  convex  and  are  separated  by  a deep  fossa, 
named  the  valley,  fig.  337,  i to  s (vallecula),  which  is  continuous  with 
the  notch  behind.  Into  this 


hollow  the  medulla  oblonga- 
ta, m,  is  received  in  front, 
and  the  falx  cerebelli  behind. 
The  under  surface  of  the  me- 
dian pottion  of  the  cerebellum 
appears  in  this  depression, 
and  is  sometimes  named  the 
inferior  vermiform  process. 

The  body  of  the  cerebellum 
at  the  surface,  and  for  some 
depth,  consists  of  numerous 
nearly  parallel  laminae  or 
folia,  which  are  composed  of 
gray  and  white  matter,  and 
might  be  compared  with  the 


An  under  view  of  the  cerebellum,  seen  from  behind, 
— the  medulla  oblongata,  m,  having  been  cut  off  a short 

ffvri  of  thp  fpcphriim  Vint  nrp  way  below  the  pons.  (Reil.)  c.  Pons  Varolii.  d.  Mid- 
gyil  U1  me  cereorum,  out  aie  die  crus  of  cerebellum,  e.  e.  Crura  cerebri,  i.  Notch 

smaller  and  not  convoluted,  on  posterior  border,  k.  Commencement  of  horizontal 

fissure.  1.  Flocculus  or  subpeduncular  lobe.  m.  Me- 
dulla oblongata  cut  through.  q io  s.  The  inferior  ver- 
miform process,  lying  in  the  vallecula,  p.  Pyramid,  r. 
Uvula,  n.  n.  Amygdal®.  s.  Nodule  or  laminated  tu- 
bercle. X.  Posterior  velum,  partly  seen.  w.  Right  and 
left  hemispheres  of  cerebellum.  3 to  7.  Nerve.s.  3.  3. 
Motores  oculorum.  5.  Trigeminal.  6.  Abducent  nerve. 
7.  Facial  and  auditory  nerves. 


These  are  separated  by  sulci 
of  difierent  depths. 

One  principal  fissure  or 
sulcus,  named  the  great  hori- 
zontal fissure,  divides  ihe  ce- 
rebellum into  an  upper  and  a 
lower  portion.  It  begins  in  front  at  the  entrance  of  the  middle  crura, 
and  passes  horizontally  backwards  around  the  outer  border  of  the 
hemispheres.  From  this  primary  fissure  numerous  others  proceed  on 


226 


THE  CEREBELLUM. 


both  the  upper  and  under  surface,  forming  parallel  curves,  having  their 
concavities  turned  forwards  and  separating  the  folia  from  each  other. 
All  these  furrows  do  not  go  entirely  round  the  hemisphere,  for  they 
often  coalesce  with  one  another  ; and  some  of  the  smaller  furrows  have 
even  an  oblique  course  between  the  others.  Moreover,  on  opening  the 
larger  fissures,  many  of  the  folia  are  seen  to  lie  concealed  within  them, 
and  do  not  reach  the  surface  of  the  cerebellum. 

Certain  fissures,  which  are  deeper  than  the  rest  and  constant  in 
their  position,  have  been  described  as  separating  the  cerebellum  into 
lobes,  which  are  thus  named  : — 

The  central  lobe,  fig.  336,  v,  situated  on  the  upper  surface,  consists 
of  about  eight  folia,  immediately  adjoining  the  anterior  concave  bor- 
der. The  superior  and  anterior  lobe,  m,  and  the  superior  and  posterior 
lobe,  u,  are  placed  between  the  central  lobe  and  the  great  horizontal 
fissure.  On  the  under  surface,  fig.  337,  ?n,  are  seen  successively  the 
inferior  posterior  lobe,  the  slender  lobe,  the  biventral  lobe,  the  amyg- 
dalce,  n,  n,  and  the  subpeduncular  lobe  or  flocculus.  This  last- 
named  lobule,  I,  I,  lobule  of  the  pneumogastric  nerve  (Vicq-d’Azyr), 
subpeduncular  lobe  (Gordon),  or  flocculus,  projects  behind  and  below 
the  middle  peduncle  of  the  cerebellum.  It  is  connected  by  a slender 
pedicle  of  white  fibres  to  the  rest  of  the  hemisphere ; but  its  exposed 
surface  is  gray,  and  is  subdivided  into  a few  small  laminae. 

Within  the  vallecula,  or  on  its  borders,  the  following  parts  are 
seen. 

Commencing  from  behind,  a conical  and  laminated  projection, 
named  the  pyramid,  is  first  met  with,  p.  In  front  of  that  is  another 
smaller  projection,  called  the  uvula,  r,  which  is  placed  between  the 
two  rounded  lobes  at  the  sides  of  the  vallecula,  named  the  amygdalae, 
n n : these  terms  being  suggested  by  a comparison  with  the  parts  so 
named  in  the  throat.  Between  the  uvula  and  amygdalae  on  each  side, 
but  concealed  from  view,  is  extended  a ridge  of  gray  matter,  indented 
on  the  surface,  and  named  furrowed  band.  Still  further  forward 
is  the  anterior  pointed  termination  of  the  inferior  vermiform  process, 
named  the  nodule,  s,  which  projects  into  the  fourth  ventricle,  and  has 
been  named  the  laminated  tubercle  (Malacarne).  On  each  side  of  the 
nodule  is  a thin  white  lamella  of  a semilunar  form,  which  is  attached 
by  its  posterior  convex  border,  and  is  free  and  concave  in  front.  The 
outer  ends  of  these  lamellae  are  attached  to  the  flocculi,  and  the  inner 
ends  to  the  nodule,  and  to  each  other  in  front  of  that  projection.  The 
two  lamellae  together  constitute  the  posterior  medullary  velum,  x,  (ve- 
lum medul.  post.),  which  has  been  compared  to  the  valve  of  Vieussens, 
— the  one  being  attached  to  the  superior  extremity  and  the  other  to 
the  inferior  extremity  of  the  middle  or  vermiform  portion  of  the  cere- 
bellum. This  posterior  velum  is  covered  in  and  concealed  by  the 
amygdalae,  and  cannot  be  properly  seen  until  those  lobules  have  been 
turned  aside. 

The  Fourth  Ventricle. — The  space  left  between  the  medulla  oblon- 
gata in  front  and  the  cerebellum  behind,  is  named  the  fourth  ventricle, 
or  ventricle  of  the  cerebellum,  fig  332,  v. 

The  cavity  of  this  ventricle  is  contracted  above  and  below,  and  is 


THE  CEREBELLUM. 


227 


widest  across  its  middle  part.  The  anterior  extremity  of  the  inferior 
vermiform  process  projects  into  it  from  behind,  and  higher  up  it  is 
covered  by  the  Vieussenian  valve.  It  is  bounded  laterally  by  the  su- 
perior peduncles,  and  lower  down  it  is  shut  in  at  the  sides  by  the  re- 
flection of  its  lining  membrane  from  the  medulla  to  the  cerebellum. 
The  upper  end  of  the  ventricle  is  continuous  with  the  Sylvian  aqueduct 
or  passage  (iter)  leading  up  to  the  third  ventricle. 

The  anterior  boundary  or  floor  of  the  fourth  ventricle,  fig.  330,  v 7, 
v'  7,  is  formed  by  the  back  of  the  medulla  oblongata  and  pons  Varolii. 
It  is  shaped  like  a lozenge,  truncated  at  its  upper  part.  Below,  it  is 
bounded  by  the  diverging  posterior  pyramids  and  restiform  bodies, 
surmounted  along  their  margin  by  a band  of  nervous  substance  called 
the  ligula.  In  the  middle  of  the  floor  is  seen  the  longitudinal  median 
fissure,  V v',  which  is  gradually  obliterated  towards  the  upper  part  of 
the  ventricle,  and  forms  at  its  lower  end,  where  it  meets  the  converging 
borders  of  the  posterior  pyramids,  the  point  of  the  calamus  scripiorhis, 
v'.  Near  this  is  the  small  orifice  alre'ady  described  as  leading  into  the 
remnant  of  the  canal  in  the  spinal  cord. 

Along  the  sides  of  the  median  fissure,  in  the  upper  part  of  the  ven- 
tricle, are  placed  two  rounded  longitudinal  eminences,  grayish  below, 
but  appearing  white  higher  up,  fig.  330.  These  are  \he  fasciculi  teretes, 
fig.  343,  a,  (faisceaux  innomines, — Cruveilhier,)  w'hich  pass  up  from 
the  medulla  along  the  back  of  the  pons  and  enter  the  cerebrum. 

Towards  the  lower  part  of  the  ventricle,  the  central  gray  matter  of 
the  medulla  is  opened  out  on  the  surface,  being  covered  only  by  a thin 
translucent  layer,  and  forms  several  small  angular  elevations,  fig.  330, 
e,  c,  i,  v',  which,  as  we  shall  hereafter  see,  have  been  recently  shown 
to  be  connected  with  the  origin  of  the  eighth,  ninth,  and  probably  the 
fifth  pair  of  nerves.  The  gray  matter  in  the  floor  of  the  fourth  ven- 
tricle has  been  named  fasciolcB  cinerece.  Upon  it,  several  transverse 
white  lines  or  striae  are  usually  observed,  passing  across  from  the 
median  fissure,  around  the  sides  of  the  restiform  bodies.  Some  of 
these  white  striae  form  part  of  the  roots  of  the  auditory  nerves,  ^ a 
few  run  slantingly  upwards  and  outwards  on  the  floor  of  the  ventricle, 
whilst  others  again  embrace  the  corresponding  half  of  the  medulla  ob- 
longata. These  transverse  lines  are  sometimes  wanting,  in  which 
case  the  white  fibres  on  which  they  depend  probably  exist  at  some 
depth  beneath  the  surface. 

The  lining  membrane  of  the  ventricle  is  continuous  with  that  of  the 
other  ventricles  through  the  aqueduct  of  Sylvius,  in  which  situation  it 
is  marked  by  delicate  rugae,  oblique  or  longitudinal  in  direction.  At 
the  sides  it  is  reflected  from  the  medulla  to  the  cerebellum,  as  already- 
stated,  and  extends  for  a considerable  distance  outwards  between  the 
flocculus  and  the  seventh  and  eighth  nerves.  At  the  lower  end  of  the 
ventricle,  this  cavity  communicates  with  the  subarachnoid  space. 
This  communication,  as  stated  by  Magendie,  may  be  generally  shown 
independently  of  laceration.  Bichat  describes  the  lower  end  of  the 
fourth  ventricle  as  being  closed  by  the  lining  membrane,  a condition 
which  may  perhaps  sometimes  exist. 

Projecting  into  the  fourth  ventricle  at  each  side,  and  passing  from 


228  13SITERNAL  STRUCTURE  OF  THE  CEREBRO-SPINAL  AXIS. 

the  point  of  the  inferior  vermiform  process  outw'ards  and  upwards  to 
the  outer  border  of  the  restiform  bodies,  are  two  small  vascular  pro- 
cesses, which  have  been  named  the  choroid  plexuses  of  the  fourth  ven- 
tricle. 

Section  of  the  cereheJlum. — Sections  of  this  part,  in  any  or  in  all  di- 
rections, show  that  the  surface  of  the  hemispheres  and  vermis,  even 
at  the  bottom  of  the  smallest  furrows,  is  composed  of  a continuous 
layer  of  gray  matter  ; and  that  the  white  medullary  substance  is  accu- 
mulated in  the  centre,  but  sends  off  numerous  thin  and  flat  processes, 
which  pass  into  the  middle  of  each  gray  lamina.  Owing  to  this  ar- 
rangement, sections  of  the  cerebellum  present  a beautifully  foliated  or 
arborescent  appearance,  which  however  is  most  perfectly  seen  on  a 
vertical  section  made  in  the  median  plane,  where  the  relative  quantity 
of  the  central  white  matter  is  small.  The  appearance  in  question  has 
been  named  arbor  vitae,  fig.  332,  /. 

In  the  lateral  hemispheres  where  the  peduncles  enter,  the  white 
matter  is  more  abundant ; and  if  a section  be  made  through  either 
hemisphere  half  way  between  its  centre  and  the  middle  of  the  vermi- 
form process,  it  will  display  a nucleus  of  gray  matter,  which  is  named 
the  corpus  dentatum  of  the  cerebellum,  fig.  338,  b.  This  presents  the 
appearance  of  a waved  line  of  yellowish-brown  matter,  surrounded  by 
white  substance  and  containing  whitish  matter  within.  This  line  is 
interrupted  at  its  upper  and  inner  part.  In  whatever  direction  the 
section  is  carried  through  the  corpus  dentatum,  this  waved  line  is  seen, 
so  that  the  dentate  body  may  be  described  as  consisting  of  a plicated 
pouch  or  capsule  of  gray  substance,  open  at  one  part  and  inclosing 
white  matter  in  its  interior,  like  the  corpus  dentatum  of  the  olivary 
body.  White  fibres  may  be  traced  out  from  it  to  the  superior  pedun- 
cles of  the  cerebellum  and  to  the  valve  of  Vieussens. 

INTERNAL  STRUCTURE  OF  THE  CEREBRO-SPINAL  AXIS. 

The  brain  and  spinal  cord  consist  of  gray  and  white  nervous  matter; 
the  former  being  also  called  the  cineritious,  or  where  it  lies  upon  the 
surface  the  cortical  substance,  and  the  latter  being  also  named  medul- 
lary. The  microscopic  structure  of  these  two  components  of  the  ner- 
vous centres  is  given  in  the  part  devoted  to  the  general  anatomy. 

Of  the  white  or  medullary  substance,  it  may  here  be  stated,  that  it 
consists  of  microscopic  fibres  arranged  into  laminse  and  bundles,  be- 
tween which  intervening  vessels  ramify.  The  existence,  course,  and 
arrangement  of  these  fibrous  plates  and  bundles,  which  are  rendered 
much  more  evident  by  hardening  the  brain  in  alcohol,  are  found  to  be 
constant  in  all  cases  ; but  our  knowledge  of  their  apparently  compli- 
cated connexions  with  each  other  and  with  the  gray  matter,  is  at 
present  imperfect  and  fragmentary;  for  which  reason,  the  subject  can 
only  be  briefly  treated  of  consistently  with  the  limits  and  purposes  of 
the  present  work.  For  more  detailed  information  the  reader  is  referred 
to  the  special  treatises  enumerated  below.* 

* Vicq-d’Azyr — Traite  de  I’Anat.  et  Physiol.,  1786;  Reil — Various  Memoirs  in  his 
Archiv.  fur  die  Physiologic;  Rolando — Sopra  la  vera  struttura  del  Cervello,  1828  ; Mayo — 
Engravings  of  Structure  of  Brain  and  Spinal  Cord,  1827  ; Solly — The  Human  Brain,  &c., 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD. 


229 


INTERNAL  STRUCTURE  OF  THE  SPINAL  CORD. 

The  general  arrangement  of  the  white  and  gray  substances  in  the 
spinal  cord  may  be  here  briefly  recapitulated. 

The  white  matter  in  each  half  of  the  cord,  is  divided  by  the  fissures 
or  by  the  gray  matter  within  into  three  columns,  fig.  326,  an  anterior, 
ae  c,  lateral,  c eb,  and  posterior,  b e p.  The  anterior  lateral  columns 
are  continuous  with  each  other  at  the  surface,  there  being  no  antero- 
lateral fissure,  and  form  in  fact  but  a single  column — the  antero-lateral 
column  ae  b.  The  posterior  columns  include  also  the  two  small  tracts 
placed  one  on  each  side  of  the  posterior  median  fissure,  sometimes 
named  the  slender  fasciculi  (see  p.  193).  The  substance  of  all  these 
columns  is  penetrated  at  intervals  by  blood-vessels,  which  are  supported 
on  fine  membranous  processes,  and  in  this  way  it  is  broken  up  into 
separate  compressed  bundles  or  into  lamelte  having  a radiated  ar- 
rangement, The  white  matter  of  the  two  halves  of  the  cord  is  continuous 
before  and  behind  the  central  gray  substance  by  means  of  the  anterior 
and  posterior  white  commissures.  Lastly,  it  may  be  mentioned  that 
the  white  substance  of  the  cord  consists  of  tubular  nervous  fibres, 
having  for  the  most  part  a longitudinal  course. 

The  gray  matter,  as  seen  on  a section,  forms  two  crescent-shaped 
masses,  turned  back  to  back  and  joined  across  the  median  plane  by 
the  gray  commissure,  figs,  326,  327.  The  small  posterior  cornu  or 
horn  of  each  crescent  reaches  the  surface  at  the  posterior  lateral 
fissure.  The  anterior  horn  is  larger  and  does  not  quite  reach  the 
surface  of  the  cord.  The  gray  matter  of  the  posterior  horn,  substantia 
gelatinosa,  has  a peculiar  microscopic  structure,  for  it  contains  no 
ganglionic  corpuscles  ; such  bodies,  however,  are  found  in  the  anterior 
cornu,  the  gray  matter  of  which  was  named  by  Rolando  substantia 
spongiosa. 

Origin  of  the  spinal  nerves. — The  anterior  and  posterior  roots  of  the 
spinal  nerves  arc  attached  along  the  sides  of  the  cord,  opposite  to  the 
corresponding  cornua  of  the  gray  matter,  fig.  326, — the  posterior  roots, 
s,  in  a perfectly  straight  line,  and  the  anterior  roots,  r,  scattered  some- 
what irregularly  upon  the  surface.  It  may  be  right  here  to  remark 
that  the  anterior  roots  contain  the  motor,  and  the  posterior  roots  the 
sensory  filaments  in  each  nerve. 

As  to  the  deep  connexions  of  these  roots,  it  has  long  been  supposed 
that  part  at  least  of  their  fibres  entered  into  or  passed  out  of  the  gray 
matter.  In  regard  to  the  posterior  roots,  this  is  easily  demonstrated, 
for  the  white  fibres  pass  at  once  into  the  tip  of  the  posterior  horn  of 
gray  matter,  in  the  posterior  lateral  fissure.  The  anterior  roots  have 
been  said  to  reach  the  anterior  gray  cornu,  by  passing  through  the 
superficial  stratum  of  white  substance  over  it ; but  actual  demonstra- 
tion of  the  fact  is  yet  wanted. 

Both  the  anterior  and  posterior  roots  are  undoubtedly  connected 

1836 ; Cruveilhier, — Anatomic  Descriptive,  1835 ; Arnold — Bemerkungeu  fiber  den  Ban 
des  Hirns,  &c.,  1838 — and  leones  Anatomicse,  Fasc.  I. ; Foville — Traite  de  I’Anat,  &c. 
du  Systeme  Nerveux  Cerebro  Spinal,  avec  planches,  1844;  Forg — Vom  innern  Baue  des 
Gehirns,  1844. 

VOL.  II. 


20 


230 


INTERNAL  STRUCTURE  OF  MEDULLA  OBLONGATA. 


with  the  white  matter  of  the  cord  ; but  there  is  considerable  difference 
of  opinion  as  to  the  precise  manner  in  which  this  connexion  takes 
place. 

According  to  one  view  (Grainger*),  both  roots  are  in  part  connected 
to  the  gray  matter,  and  in  part  to  the  lateral  column  only  of  the  white 
substance.  Now,  in  regard  to  the  anterior  roots,  from  the  scattered 
manner  in  which  they  arise,  it  is  plain  that  they  cannot  well  be  limited 
as  to  their  place  of  origin  in  the  manner  alleged,  but  that  some  of  their 
filaments  are  connected  with  the  anterior  column.  As  to  the  posterior 
roots,  they  are  mostly  attached  to  the  lateral  column,  but  in  some  parts 
of  the  cord,  they  undoubtedly  are  connected  also  with  the  posterior 
column.  This  indeed  corresponds  with  Bellingeri’s  opinion,  who 
believes  that  each  root  (both  anterior  and  posterior)  has  three  deep 
connexions,  one  with  the  gray  matter  and  one  with  each  of  the  adja- 
cent white  columns ; but,  as  already  stated,  the  anterior  roots  have 
not  yet  been  satisfactorily  traced  into  the  gray  substance. 

The  course  of  the  white  fibres  of  the  nerves  within  the  cord  is  not 
yet  clearly  made  out.  Those  which  enter  the  gray  matter  are  believed 
by  some  (Grainger)  to  terminate  there ; whilst  it  has  been  generally 
supposed  that  those  which  are  connected  with  the  white  substance 
ascend  continuously  up  the  cord  to  reach  the  brain.  Others  again 
believe  (with  Valentin)  that  the  fibres  which  enter  the  gray  matter 
are  prolonged  for  some  way  upwards  among  its  ganglionic  corpuscles, 
and  then  pass  into  the  white  columns,  with  which  they  at  length  be- 
come continuous. 

The  recently  published  views  of  Drs.  Stilling  and  Wallach  are  totally  different 
from  those  above  mentioned.  According  to  these  observers,  the  roots  of  the 
nerves  have  no  direct  connexion  with  the  white  matter,  and  none  of  them  run 
upwards  in  the  cord.  On  the  contrary,  the  fibres  of  all  four  roots  enter  the  gray 
matter,  and  run  horizontally  through,  in  such  a manner  as  to  be  completely  inter- 
laced or  intermixed  within  it.  Thus,  to  follow  one  of  the  posterior  roots,  it  is  said 
that,  having  entered  the  corresponding  gray  cornu,  its  fibres  are  disposed  in  three 
ways; — some,  keeping  on  the  same  side  of  the  cord,  pass  forwards  through  the 
anterior  cornu  and  form  part  of  the  anterior  root  of  that  side  ; whilst  others, 
crossing  through  the  gray  commissure  into  the  opposite  half  of  the  cord,  run 
through  its  two  gray  cornua  and  assist  in  forming  its  anterior  and  posterior  roots. 
The  fibres  of  all  four  roots  have  a similar  arrangement,  so  that  some  fibres  of  each 
root  are  continuous  with  some  of  the  other  three. 

It  is  to  be  observed,  however,  that  the  method  of  investigation  pursued  by 
Stilling  and  Wallach,  viz.,  that  of  examining  thin  transverse  sections  of  the  cord 
by  means  of  a low  power  of  the  microscope,  is  not  well  adapted  to  determine 
the  connexion  and  course  of  the  nervous  fibres.  Moreover,  it  has  ,been  shown, 
by  subsequent  observations  made  on  the  spinal  cord  of  the  frog,t  for  the  purpose 
of  testing  the  accuracy  of  Stilling’s  views,  that  the  roots  of  the  nerves  pass  at 
least  a short  distance  upwards,  and  that,  at  any  rate,  some  of  their  white  fibres 
are  continuous  with  the  longitudinal  fibres  of  the  cord. 

It  must  be  remembered,  however,  that  there  is  no  direct  anatomical 
evidence  to  prove,  that  the  fibres  are  continued  all  the  way  up  to  the 
brain. 

INTERNAL  STRUCTURE  OF  THE  MEDULLA  OBLONGATA. 

The  white  and  gray  constituents  of  the  spinal  cord,  when  they  have 
* On  the  Spinal  Cord.  1837.  t Budge — Muller’s  Archiv.,  1844,  p.  160. 


INTERNAL  STRUCTURE  OF  MEDULLA  OBLONGATA. 


231 


reached  the  medulla  oblongata  become  increased  in  size,  and  are 
altered  in  their  arrangement,  in  the  manner  now  to  be  described. 
The  three  white  columns  of  the  cord  are  disposed  as  follows. 

1.  The  posterior  column,  figs.  342,  343,  e,  consisting  of  the  fasciculus 
cuneatus  and  the  slender  fasciculus  which  higher  up  is  named  poste- 
rior pyramid,  forms  the  restiform  body.  Thi^,  being  joined  by  some 
fibres  from  the  lateral  column,  and,  as  indicated  by  Solly,  by  a few 
from  the  anterior  column,  enters  the  cerebellum  as  its  inferior  peduncle, 
fig.  338,  r, — the  part  called  the  posterior  pyramid,  p,  fig.  343,  excepted, 


[Fig.  338. 


Analytical  diagram  of  the  encephalon — in  a vertical  section.  (After  Mayo.) 
s.  Spinal  cord.  r.  Restiform  bodies  passing  to  c,  the  cerebellum,  d.  Corpus  dentatum  of  the 
cerebellum,  o.  Olivary  body.  f.  Columns  continuous  with  the  olivary  bodies  and  central  part 
of  the  medulla  oblongata,  and  ascending  to  the  tubercula  quadrigemina  and  optic  thalami.  p. 
Anterior  pyramids.  «.  Pons  Varolii.  n,  6.  Tubercula  quadrigemina.  g.  Geniculate  body  of  the 
optic  thalamus,  t.  Processus  cerebelli  ad  testes,  a.  Anterior  lobe  of  the  brain,  o.  Posterior  lobe 
of  the  brain. — T.  & B.] 

which  according  to  careful  inquirers*  passes  up  with  the  fasciculi 
teretes  to  the  cerebrum. 

* Burdach — Bau  und  Leben  des  Gehirns,  1819  ; Arnold, — Foville, — Forg — Operibus 
citatis. 


232 


INTERNAL  STRUCTURE  OF  MEDULLA  OBLONGATA. 


2.  The  lateral  column  ascends  towards  the  base  of  the  olivary  body, 
and  is  disposed  of  in  three  ways;  some  of  its  fibres  from  the  surface 
and  deep  part  join  in  the  restiform  body  and  go  to  the  cerebellum  ; a 
larger  number,  fig.  341,  x,  come  forwards  between  the  anterior  co- 
lumns, and  crossing  the  median  plane,  form  the  chief  part  of  the  oppo- 
site anterior  pyramid,  b;  the  remaining  fibres  pass  up  to  the  cerebrum, 
as  the  fasciculi  teretes,  (fig.  338,  behind  f ; faisceaux  innomines,) 
appearing  on  the  back  of  the  pons  Varolii,  in  the  upper  part  of  the 
floor  of  the  fourth  ventricle,  fig.  343,  a. 

3.  The  anterior  columns,  having  reached  the  apex  of  the  anterior 
pyramids,  are  thrust  aside  from  their  median  position  by  the  decussa- 
ting fibres  derived  from  the  lateral  columns,  and  are  then  distributed 
in  three  divisions.  One,  very  small,  ascends  obliquely  backwards 
beneath  the  olive,  and  joins  the  restiform  body  (Solly).  Another  divi- 
sion passes  directly  up,  its  fibres  embracing  the  olivary  nucleus,  fig. 
338,  above  which  they  are  again  collected  together,  and  joined  by 
other  fibres  arising  from  the  corpus  dentatum,  so  as  to  form  the  olivary 
fasciculus,/;  this  ascends  through  the  pons  and  at  the  side  of  the 
cerebral  peduncle  under  the  name  of  the  fillet,  fig.  342,  c,i,li,  and  reaches 
the  corpora  quadrigemina  by  i,  and  the  cerebral  hemispheres  by  li. 
The  remaining  division  of  the  anterior  column  ascends  into  the  ante- 
rior pyramid,  p,  fig.  338,  forming  its  outer  part.  The  anterior  pyra- 
mids, therefore,  are  composed  of  fibres  from  the  lateral  and  anterior 
columns,  and  are  continued  up  through  the  pons  into  the  peduncles  of 
the  cerebrum. 

It  is  to  be  remembered,  however,  that  the  separation  between  these 
different  tracts  of  white  fibres  cannot  be  clearly 
followed  out  through  the  whole  structure  of  the 
medulla  oblongata ; for,  at  a certain  depth  from 
the  surface,  they  are  found  to  be  more  or  less 
blended  with  one  another. 

Gray  matter  of  the  medulla  oblongata. — In  as- 
cending into  the  medulla  oblongata,  the  gray  matter 
becomes  more  abundant,  and  gets  blended  with  all 
the  white  fasciculi,  excepting  the  anterior  pyra- 
mids, fig.  339,  h b,  which  are  composed  entirely 
of  white  substance.  The  posterior  horns  increase 
in  size,  and  are  directed  more  to  the  side,  where 
they  appear  at  the  surface  in  the  form  of  a narrow 
gray  stripe,  which  was  called  by  Rolando,  tuberculo 
Section  of  the  medulla  c-mereo,  d.  A distinct  mass  of  gray  substance, 
obiongam  — natural  size  forming  the  corpus  dentatum,  c c,  exists  within  the 

— (Arnold).  A.  About  , Vru  • r .L  J 

middle  of  medulla.  B.  olivary  body.  Ihe  gray  commissure  of  the  cord. 

Higher  up  a.  Anterior  jg  continued  Upwards,  becoiTies  exposed  at 

■ fissure.  6.  Anterior  pyra-  , , , p • ..i  n r a 

mid.  c.  Olivary  body  the  back  ot  the  medulla,  p p,  in  the  floor  ot  tlie 

and  corpus  dentatum.  fourth  Ventricle,  Owing  to  the  divergence  of  the 
d.  Gray  lubercle.  p.  . , ° ,. 

Posterior  fissure  in  fioor  posterior  white  lasciculi ; and  it  eventually  disap- 

offourih ventricle, where  pears  as  a distinct  median  structure,  being  mixed 
late;^d.  With  the  white  fibres  ot  the  fasciculi  teretes. 

According  to  the  observations  of  Stilling,  some 


Fig.  339. 

A 


INTERNAL  STRUCTURE  OF  MEDULLA  OBLONGATA. 


233 


part  of  the  gray  matter  at  the  back  of  the  medulla,  forms  special  de- 
posits or  nuclei,  connected  with  the  roots  of  the  spinal  accessory, 
vagus,  glosso-pharyngeal  and  hypoglossal  nerves.  Of  these  nuclei, 
the  first  or  lowest  is  concealed  in  the  substance  of  the  medulla ; whilst 
those  which  are  situated  higher  up  gradually  appear  as  small  triangular 
eminences,  in  the  floor  of  the  fourth  ventricle,  near  the  point  of  the  cala- 
mus scriptorius. — See  fig.  330,  in  which  v'  shows  the  position  of  the 
nucleus  for  the  spinal  accessory,  i that  for  the  vagus,  e that  for  the 
glosso-pharyngeal,  and  c that  for  the  hypoglossal  nerve.  The  first 
nucleus  is  that  for  the  spinal  accessory  nerve.  It  reaches  some  way 
down  in  the  cord,  and  then  appears,  on  a transverse  section,  like  a 

[Fig.  340. 


Transverse  section  of  the  medulla  oblongata  through  the  lower  third  of  the  olivary  bodies. 
(From  Stilling.)  Magnified  4 diameters. 

a.  Anterior  fissure,  b.  Fissure  of  the  calamus  scriptorius.  c.  Raphe,  d.  Anterior  columns, 
e.  Lateral  columns.  /.  Posterior  columns,  g.  Nucleus  of  the  hypoglossal  nerve,  containing 
large  vesicles,  h.  Nucleus  of  the  vagus  nerve.  i,i.  Gelatinous  substance.  k,li.  Roots  of  the 
vagus  nerve.  1.  Roots  of  the  hypoglossal,  or  ninth  nerve,  m A thick  bundle  of  white  longi- 
tudinal fibres  connected  with  the  root  of  the  vagus,  n.  Soft  column  (Zardtlm/ig,  Stilling),  o. 
Wedge-like  column  (Keelstrang,  Stilling),  p.  Transverse  and  arciform  fibres,  q.  Nucleus  of 
the  olivary  bodies,  r.  The  large  nucleus  of  the  pyramid,  s,  s,  s.  The  small  nuclei  of  the  pyra- 
mid. u.  A mass  of  gray  substance  near  tbe  nucleus  of  the  olives  (flliven-Nebenkern).  u,  q,  r,  are 
traversed  by  numerous  fibres  passing  in  a transverse  semicircular  direction,  v,  w.  Arciform  fibres. 
X.  Gray  fibres. — T.  & B.] 


lateral  process  extending  from  the  gray  crescent  between  its  anterior 
and  posterior  horns,  and  from  it  the  slender  and  straggling  roots 
of  the  nerve  run  outwards  to  the  surface;  as  it  extends  upw'ards,  it 
approaches  the  middle  and  back  part  of  the  medulla  oblongata,  v'. 

20* 


234 


INTERNAL  STRUCTURE  OF  PONS  VAROLIl. 


In  front  of  this  nucleus,  and  close  to  the  centre  of  the  medulla,  is 
another,  the  second,  fig.  340,  g,  commencing  higher  up  and  con- 
nected with  the  hypoglossal  nerve,  the  roots  of  which,  coming  for- 
W'ards  between  the  anterior  pyramid  and  the  olivary  body,  appear 
at  the  surface  in  the  depression  between  those  parts.  Continuing 
to  ascend,  these  two  nuclei  reach  the  back  of  the  medulla,  and  then 
make  their  appearance  in  the  floor  of  the  fourth  ventricle.  Higher 
up,  the  nucleus  for  the  spinal  accessory  nerve  is  succeeded  by  a third 
in  the  same  line,  h,  which  is  connected  with  the  nervus  vagus,  and  is 
also  placed  to  the  outer  side  of  that  for  the  hypoglossus,  g.  Further 
out,  z.  fourth  nucleus,  n,  begins  to  be  observed,  belonging  to  the  glosso- 
pharyngeal nerve.  Tlie  last  change  in  the  arrangement  of  these 
small  gray  masses  consists  in  the  gradual  narrowing  of  the  nucleus  of 
the  par  vagum,  and  the  approximation  of  those  for  the  hypoglossal 
and  glosso-pharyngeal  nerves,  which  were  chiefly  separated  by  it. 

Langenbeck  and  Forg  maintain,  that  the  part  regarded  by  Stilling 
as  the  nucleus  for  the  glosso-pharyngeal  nerve,  is  really  the  place  of 
origin  of  the  greater  root  of  the  fifth  or  trigeminal  nerve. 

The  horizontal  white  fibres  w'hich  form  the  antero-posterior  septum, 
fig.  340,  c,  in  the  medulla  oblongata,  will  be  described  along  with  a 
similar  set  of  fibres  existing  in  the  pons. 


INTERNAL  STRUCTURE  OF  THE  PONS  VAROLIL 


The  pons  Varolii  consists  of  transverse  white  fibres,  and  of  the 
longitudinal  fibres  prolonged  through  them  from  the  medulla,  inter- 
mixed with  much  gray  matter. 

On  dissecting  it  from  the 
Fig.  341.  front,  a superficial  white 

layer,  figs.  34 1 , 342,  m,  also 
fig.  329,  p,  i,  is  met  with, 
which  extends  on  either 
side  into  the  middle  crus 
of  the  cerebellum.  Behind 
this  are  seen  the  prolonged 
fibres  of  the  anterior  pyra- 
mids, b,  which,  as  they 
ascend  through  the  pons, 
are  widely  separated  into 
smaller  bundles,  intersected 
by  other  transverse  white 
, ^ u,  . 1 , • fibres,  m',  which,  like  those 

Fibres  of  medulla  oblongata  and  pons,  arranged  in  i.  r 

alternate  layers. — (Arnold.)  6.  Anterior  pyramid.  f.  Upon  the  SUrtace,  are  COn- 
Prolongation  of  same  through  pons.  c.  Olivary  bundle,  tinued  into  the  Cerebellum. 
d.  Olive,  m'.  Deeper  transverse  fibres,  m".  Prolonged  , , . j 

as  middle  peduncle  of  cerebellum,  p,  g.  Their  continua-  AmongSt  tfiese  tWO  ueCUS- 
tion  into  laminae  or  folia  of  same.  n.  Inferior  peduncle,  gating  sets  of  fibres  is  a 
a:.  Decussating  portion  of  left  lateral  column,  crossing  over  , ° r . 

to  right  anterior  pyramid.  large  quantity  of  gray  mat- 


ter. 


The  arrangement  just  described  extends  to  a considerable  depth  in 
the  pons,  but  is  succeeded  by  a third  layer,  which  consists  entirely  ol 
longitudinal  fibres.  This  comprehends  the  olivary  fasciculus,  fig.  342, 


235 


INTKRNAL  STRUCTURE  OF  CEREBELLUM. 

c,  i,  h,  and  the  fasciculi  teretes,  t,  which,  as  we  have  frequently  men- 
tioned, run  up  on  each  side  and  in  the  floor  of  the  fourth  ventricle, 
intermixed  with  much  gray  substance. 

Septum  of  the  medulla  oblongata  and  pons. — Besides  the  white 
fibres  already  described,  there  exist  in  the  medulla  oblongata  and  pons 
others  which  extend  from  behind  forwards,  fig.  340,  i,  in  the  median 
plane.  In  the  medulla,  fig.  332,  these  appear  above  the  decussation  of 
the  pyramids.  Some,  issuing  from  the  anterior  fissure  and  turning 
round  the  sides  of  the  medulla,  form  the  arciform  fibres,  and  those 
(sometimes  named  jibrce  transversce)  which  occasionally  cover  the 
anterior  pyramids  and  olivary  bodies  ; others,  appearing  at  the  sur- 
face, in  the  floor  of  the  fourth  ventricle,  give  rise  to  the  transverse 
white  strim  generally  seen  in  that  situation.  These  parts  have  been 
already  described  (p.  201). 

A median  septum  of  the  same  kind,  obviously  exists  throughout  the 
whole  height  of  the  pons,  in  its  back  part,  but  becomes  indistinct  in 
approaching  the  front  or  basilar  surface,  except  towards  its  upper  and 
lower  edge,  where  the  superficial  fibres  of  the  pons  are  manifestly 
continuous  in  the  median  line  with  these  septal  fibres ; and  bundles  of 
white  fibres,  belonging  to  the  same  system,  encircle  the  crura  cerebri 
at  their  emergence  from  the  upper  border  of  the  pons. 

According  to  Fovifle,  a few  of  the  fibres  from  each  of  the  three  principal  lon- 
gitudinal elements  of  the  medulla  turn  forwards  and  become  continuous  with 
the  transverse  fibres  of  the  pons ; and,  in  like  manner,  one  or  more  small  bundles 
horn  each  of  the  cruri  cerebri  take  a similar  transverse  course.* 

INTERNAL  STRUCTURE  OF  THE  CEREBELLUM. 

The  cerebellum  consists  of  an  internal  white  medullary  mass,  con- 
taining on  each  side  the  corpus  dentatum  ; of  an  external  gray  or 
cortical  layer,  covering  the  leaves  or  folia  ; and  of  three  pairs  of  white 
peduncles. 

The  folia  consist  of  white  matter  covered  externally  with  gray.  The 
structure  of  each  of  them  appears  to  be  this : — from  the  central  white 
mass  of  the  cerebellum,  thin  plates,  composed  of  white  fibres,  pass  up 
in  the  centre  of  the  folia,  and  divide  into  subordinate  white  laminae, 
corresponding  with  the  subdivisions  of  the  folia.  Many  of  these  cen- 
tral white  lamincB  can  be  traced  continuously  from  the  peduncles  of 
the  cerebellum.  Upon  these  central  plates  are  laid  other  collateral  la- 
mellae, which  are  not  connected  with  the  fibres  proceeding  from  the 
middle  of  the  cerebellum,  but  merely  pass  fi’om  one  folium  to  another. 
Superficial  to  these  w’hite  fibres  is  the  gray  cortical  substance. 

This  gray  matter  is  not  uniform  throughout  its  whole  thickness,  but  is 
composed  of  two  or  more  layers,  differing  in  colour  and  other  charac- 
ters ; — resembling,  in  this  respect,  the  cortical  substance  of  the  poste- 
rior convolutions  of  the  cerebrum. 

The  lohite  fibres,  composing  the  peduncles  of  the  cerebellum,  are 
thus  arranged  in  its  interior. 

The  middle  peduncles,  fig.  341,  ?w,  which  are  the  most  superficial, 

* Foville,  op.  cit,  PI.  ii.,  figs.  2 and  3.  PI.  in.,  figs.  5 and  6. 


236  INTERNAL  STRUCTURE  OF  CEREBRUM. 


pass  from  the  pons  Varolii,  with  the  transverse  fibres  of  which  they 

are  directly  continuous,  and  enter 
Fig.  342.  the  lateral  parts,  m,  p,  of  the  ce- 

rebellum. They  may  be  traced 
into  the  folia  of  those  parts,  q, 
and  form  a large  share  of  each 
hemisphere. 

The  middle  peduncles  being 
removed,  the  inferior  peduncles 
(restiform  bodies)  come  into  view, 
figs.  338,  341,  3 1 2,  n.  They  pass 
upwards  into  the  middle  part  of 
the  cerebellum,  in  the  folia  of 
Arrangement  of  columns  of  medulla;  and  of  whlch  they  are  distlibuted,  espe- 
superior  and  infej;ior  peduncles  of  cerebellum,  cially  tO  those  of  the  Upper  Sur- 
face. 

The  superior  peduncles,  figs. 
338,  t,  342,  r,  which  are  placed 
nearest  to  the  middle  line,  are 
principally  connected  with  the 
folia  of  the  inferior  vermiform 
process ; but  a considerable  num- 
ber of  them  pass  into  or  issue 
from  the  gray  capsule  of  the  cor- 
pus dentatum,  which  has  been  already  described. 


— (Arnold.)  a.  Pari  of  the  anterior  column, 

which  ascends  to  the  olive,  b.  Decussating  por- 
tion oflaleral  column,  c.  Olivary  fasciculus,  d. 
Olive,  e.  Reslilorm  body.  /,  g.  Corpora  quad- 
rigemiiia.  c,  h,  i.  Fillet,  h.  Part  which  goes  to 
cerebral  peduncle.  i.  Part  going  to  corpora 
quadrigemina.  m m'.  Transverse  fibres  of  pons, 
cut  through,  tr.  Inferior  peduncle  of  cerebellum, 
o.  Septal  fibres  of  medulla  oblongata.  q q. 
Fibres  of  inferior  peduncle  continued  into  cere- 
bellum. r r.  Superior  peduncle,  a.  Thala- 
mus. V.  Corpus  albicans. 


INTERNAL  STRUCTURE  OF  THE  CEREBRUM. 

The  fibres  of  the  cerebrum,  though  exceedingly  complicated  in  their 
arrangement,  and  forming  many  different  collections,  may  be  referred 
to  three  principal  syslems,  according  to  the  general  course  which  they 
take,  viz., — 1.  Ascending  or  peduncular  fibres,  pass  up  from  the 

medulla  oblongata  to  the  hemispheres,  and  constitute  the  two  crura  or 
peduncles  of  the  cerebrum.  They  increase  in  number  as  they  ascend 
through  the  pons,  and  still  further  in  passing  through  the  optic  tha- 
lami,  and  striated  bodies,  beyond  which  they  spread  in  all  directions 
into  the  hemispheres.  These  were  named  by  Gall  the  diverging  fibres. 
2.  Transverse  or  commissural  fibres,  which  connect  the  two  hemi- 
spheres together.  These  are  the  converging  fibres  of  Gall.  3.  Longi- 
tudinal or  collateral  fibres,  which,  keeping  on  the  same  side  of  the 
middle  line,  connect  more  or  less  distant  parts  of  the  same  hemisphere 
together. 

1.  The  peduncular  fibres  consist  of  a main  body  and  of  certain 
accessory  bundles  of  fibres. 

a.  The  main  body  on  each  side  is  derived  from  the  anterior  pyra- 
mid, fig.  338,  p,  from  the  prolongation  of  the  lateral  column  (one  of  the 
fasciculi  teretes,  fig.  343,  a,)  and  from  the  posterior  pyramid,  p.  After 
it  has  passed  through  the  pons  and  become  increased  in  amount,  it  is 
separated  into  two  parts  in  the  crus  cerebri  by  a layer  of  dark  cineri- 
tious  matter,  named  locus  niger.  The  lower  or  superficial  part,  which 
is  derived  from  the  pyramid,  consists  almost  entirely  of  white  fibres,  col- 


INTERNAL  STRUCTURE  OF  CEREBRUM. 


237 


lected  into  coarse  fasciculi, 
and  is  named  the  crust  or 
basis,  fig.  343,  g,  or  the  fas- 
ciculated 'portion  of  the  pe- 
duncle (Foville).  The  upper 
part,  composed'  principally 
of  the  fasciculus  teres  and 
posterior  pyramid,  is  named 
the  tegmentum,  h ; it  is  softer 
and  finer  in  texture,  and  is 
mixed  with  much  gray  mat- 
ter. 

Still  increasing  in  number 
within  the  peduncle,  these 
two  sets  of  fibres  continue 
to  ascend,  fig.  338,  and  pass 
abovethe  optictracts  through 
the  thalamus,  fig.  343,  b,  I, 
and  corpus  striatum,  k,  h. 

Receiving  fresh  accessions 
of  fibres  there,  they  are  con- 
tinued on  into  the  medullary 
substance  of  the  correspond- 
ing hemisphere,  fig.  338. 

The  anterior  fibres,  or  those 
of  the  crust,  fig.  343,  g,  pass 
principally,  if  not  entirely, 
through  the  corpus  striatum. 

The  posterior  fibres,  or  those 
of  the  tegmentum,  run,  some 
through  the  thalamus,  but  the  greater  part  at  least  through  the  corpus 


Back  view  of  peduncular  fibres  of  cerebrum,  attached 
to  hemispheres. — (Arnold.)  a.  Fasciculus  teres  of  left 
side.  b.  Fibres  of  tegmentum  ascending  through  thala- 
mus. c.  Left  corpora  quadrigemina.  e.  Restiform 
body.  //.  Superior  peduncles  of  cerebellum — processus 
ad  testes,  g.  Fibres  of  crust,  ii.  Fillet  of  both  sides. 
k k'.  Corpora  striata: — on  the  right  side,  the  gray  mat- 
ter stripped  off  to  show  radiating  fibres  of  fibrous  cone. 
1.  Left  thalamus,  m m.  Sections  of  middle  peduncles 
of  cerebellum,  n.  Section  of  left  inferior  peduncle,  p. 
Left  posterior  pyramid.  9.  Corpus  callosum,  s.  Under 
surface  of  the  same — below  s,  cavity  of  fifth  ventricle. 
t.  Left  anterior  pillar  of  fornix,  y y.  Decussation  of 
radiating  fibres,  with  those  of  corpus  callosum. 


striatum  also. 


As  they  pass  through  these  large  gray  masses  or  ganglia,  the  two 
sets  of  fibres  intersect  or  cross  each  other,  and  on  emerging  beyond 
the  gray  matter,  fig.  343,  y,  they  again  decussate  with  the  commissural 
fibres  or  transverse  fibres,  s,  of  the  corpus  callosum,  q.  After  that, 
they  spread  into  the  hemisphere  in  every  direction,  and  reach  the  cor- 
tical substance  of  the  convolutions. 


The  accessory  fibres  of  the  peduncular  system  are  as  follows : — 

b.  The  superior  peduncles  of  the  cerebellum,  (processus  ad  testes,) 
figs.  338,  343,/,  which  are  continued  up  beneath  the  corpora  quadrige- 
inina,  q,  c,  and  form  part  of  the  tegmentum. 

c.  The  bundle  of  fibres  on  each  side,  named  the  fillet,  lemniscus, 
schleife,  i. — This,  which  is  originally  derived  from  the  anterior  co- 
lumn of  the  cord,  forms  the  olivary  fasciculus,  fig.  342,  c,  of  the  me- 
dulla oblongata,  as  previously  described.  Reinforced  by  fibres  from 
the  corpus  dentatum  of  the  olivary  body,  d,  it  ascends  through  the 
back  part  of  the  pons,  still  increasing  in  size.  Appearing  at  the  side 
of  the  cerebral  peduncle,  above  the  upper  border  of  the  pons,  fig.  343, 
i,  i,  it  divides  into  two  portions,  of  which  one,  fig.  342,  i,  crosses  over 


238 


INTERNAL  STRUCTURE  OF  CEREBRUM. 


the  superior  peduncle  of  the  cerebellum  to  the  corpora  quadrigemina, 
meeting  its  fellow  of  the  opposite  side;  whilst  the  other,  h,  is  continued 
upwards  with  the  fibres  of  the  tegmentum. 

d.  Other  accessory  fibres  to  the  peduncles  take  their  rise  in  the  gray 
matter  of  the  corpora  quadrigemina,  g,/,  (the  brachial^  and  proceed 
on  to  the  thalami,  u. 

e.  Lastly,  another  set,  having  a similar  destination,  are  derived  from 
the  corpora  geniculata. 

Corpus  striatum  and  corona  radiata. — The  principal  mass  of  each 
corpus  striatum  is  concealed  in  the  substance  of  the  cerebral  hemisphere, 
whilst  a part  of  it,  fig.  343,  k,  k,  appears  in  the  lateral  ventricle.  The 
ascending  white  fibres  of  the  corresponding  peduncle,  spreading  out 
in  a radiating  manner,  pass  up  through  and  between  these  two  parts 
of  the  corpus  striatum,  and  divide  the  gray  matter  into  an  extra-  and 
an  intra-ventricular  portion. 

The  assemblage  of  these  radiating  fibres,  fig.  338,  might  be 
compared  to  a fan,  bent  into  the  form  of  an  incomplete  hollow 
cone,  having  its  concave  surface  turned  downwards  and  outwards ; 
hence  the  name  corona  radiata  applied  to  them  by  Reil,  d,nA  fibrous 
cone,  by  Mayo.  On  cutting  through  the  corpus  striatum  across  the 
direction  of  these  fibres,  the  section  of  the  fibrous  cone  appears  as 
a broad  white  band,  extending  from  the  anterior  to  the  posterior 
extremity  of  that  gray  mass,  and  separating  it  into  its  outer  and 
inner  portions  already  mentioned.  On  dissecting  the  corpus  striatum 
from  the  ventricle,  and  removing  its  intraventricular  gray  substance, 
we  meet,  at  some  depth  from  the  surface,  with  these  white  fibres, 
which  being  intermixed  with  the  gray  matter,  give  to  the  body  its 
streaked  appearance.  The  extraventricular  portion,  which  lies  some- 
what lower  than  the  inner  portion,  is  situated  between  the  radiating 
peduncular  fibres,  and  the  island  of  Reil,  and  may  be  exposed  by  dis- 
secting the  hemisphere  from  the  Sylvian  fissure.  In  this  dissection, 
the  convolutions  of  the  island  are  first  rernoved ; beneath  the  white 
matter  of  those  gyri,  a thin  layer  of  gray  substance  is  met  with,  which 
has  been  named  the  claustrum  (Burdach) : deeper  than  this,  white 
matter  again  appears, — forming,  however,  but  a very  thin  layer, — on 
removing  which  the  extraventricular  portion  of  the  corpus  striatum  is 
exposed.  In  this  dissection  the  striated  body  is  also  seen  to  be  conti- 
nuous below  with  the  anterior  perforated  space,  where  the  gray  matter 
reaches  the  surface  of  the  brain  ; whilst  around  its  upper  margin,  now 
completely  exposed,  appears  a zone  of  white  radiating  fibres,  which 
is  the  continuation  of  the  corona  radiata,  after  its  passage  through  the 
gray  matter.  On  next  scraping  away  the  latter,  the  fibrous  cone  is 
entirely  displayed  from  its  outer  side.  In  doing  this,  the  fibres  of  the 
anterior  commissure,  of  which  we  shall  presently  make  mention,  also 
come  into  view. 

Lastly,  it  may  be  mentioned,  that  if  the  brain  be  cut  through  in  a 
plane  perpendicular  to  the  surface  of  the  island,  the  section  of  the  gray 
layer,  named  the  claustrum,  appears  as  a narrow  dark  line  situated 
between  the  island  and  the  corpus  striatum. 


INTERNAL  STRUCTURE  OF  CEREBRUM. 


239 


2,  The  transverse,  commissural  or  connecting  fibres  of  the  cerebrum 
include  the  following  sets  : — 

a.  The  cross  fibres  of  the  corpus  callosum,  fig.  343,  q. — These  are 
more  numerous  at  each  end  of  thecoi’pus  callosum  than  in  the  middle, 
and  form  the  thickest  mass  behind.  Passing  laterally  into  the  sub- 
stance of  the  hemispheres,  some  are  directed  upwards,  whilst  others 
spread  outwards  on  the  roof  of  the  lateral  ventricles,  forming  there 
what  is  named  the  tajyetum,  s.  Having  next  intersected  the  pedun- 
cular radiating  fibres  at  y y,  they 
then  spread  out  into  the  hemi- 
spheres,  reaching  the  gray  matter 
of  the  convolutions. 

h.  The  anterior  commissure,  fig. 

344,  X. — This  is  a round  bundle  of 
white  fibres,  seen  in  the  fore  part 
of  the  third  ventricle,  from  which 
it  passes  laterally  into  the  corpora 
striata,  and  bending  backwards, 
extends  a long  way  in  the  hemi- 
spheres, reaching  into  the  middle 
lobe  on  each  side. 

c.  The  posterior  commissure, 
also  situated  in  the  third  ventricle,  ' 
runs  through  the  optic  thalami, 
and  is  soon  lost  in  the  substance 
of  the  hemispheres  in  that  situa- 
tion. 

3.  The  third  system  of  fibres  in 
the  cerebrum,  the  longitudinal  or 
collateral,  may  be  comprehended 
under  the  following  heads. 

a.  The  fornix,  fig.  345,  t t'. — 

This  forms  a longitudinal  bundle 
on  each  side,  which,  as  already 
mentioned,  might  be  described  as 
commencing  in  the  thalamus,  *, 
near  its  anterior  tubercle.  It  then 
descends  to  the  corpus  albicans, 
n,  of  its  own  side,  turns  round  in 
that  eminence,  and  ascending  to 
form  the  anterior  pillar,  t,  may 
thence  be  traced  backwards  in 
conjunction  with  that  of  the  opposite  side,  until  it  separates  posteri- 
orly, where  it  spreads  out  in  part  upon  the  pes  hippocampi  in  the  de- 
scending cornu  of  the  lateral  ventricle,  and  is  prolonged  as  the  corpus 
fimbriatum  nearly  to  the  point  of  the  middle  lobe. 

h,  c.  The  white  fibres  constituting  the  tcenia  semicircularis,  fig.  333, 
s,  and  those  of  the  peduncles  of  the  pineal  gland,  fig.  336,  p,  may  per- 
haps be  regarded  as  accessories  to  the  fornix.  They  both  join  its 
anterior  pillars  in  front.  Behind,  the  taenia  is  lost  on  the  back  of  the 


Under  surface  of  left  hemisphere  dissected. 
— (After  Mayo.)  a.  Anterior,  and  a',  posterior 
part  of  fillet  of  corpus  callosum,  b,  g.  Section 
of  cerebral  peduncle,  b.  Tegmentum,  g. 
Crust,  separated  by  locus  niger.  d.  Fibres 
reaching  from  back  of  corpus  callosum  to  pos- 
terior lobe.  e.  Fasciculus  uncinatus,  connect- 
ing anterior  and  middle  lobes,  across  the  Syl- 
vian fissure.  / f.  Transverse  fibres  from  corpus 
callosum.  1.  Back  of  thalamus,  m.  Corpus 
albicans,  q.  Corpus  callosum,  r.  Radiating 
fibres  of  hemisphere,  t.  Anterior  pillar  of  for- 
nix. V.  Collateral  fibres  of  convolutions,  x. 
Anterior  commissure.  2.  Part  of  optic  tract. 


240 


INTERNAL  STRUCTURE  OF  CEREBRUM. 


thalamus  in  the  descending  cornu  ; and  the  pineal  peduncles  end  in  the 
pineal  gland,  so  that  they  are  regarded  by  some  as  forming  a trans- 
verse commissure. 

FoviUe  traces  the  tasnia  from  part  of  the  posterior  pyramids,  as  will  be  pre- 
sently noticed. 

d.  The  stricB  longitudinales,  upon  the  upper  surface  of  the  corpus 
callosum,  also  belong  to  this  system.  They  are  distinguished  into  the 
middle  and  lateral  longitudinal  striae.  In  front,  they  are  connected 
with  the  peduncles  of  the  corpus  callosum,  and  through  them  with  the 
anterior  perforated  space.  Their  posterior  connexions  are  uncer- 
tain ; according  to  Foville,  they  join  the  posterior  pillars  of  the  fornix, 

e.  Fibres  of  the  gyrus  fornicatus ; fillet  of  the  corpus  callosum  (Mayo). 
These  fibres  constitute  the  white  substance  of  the  gyrus  fornicatus, 
and  take  a longitudinal  course,  fig.  345,  a a'  a a!',  immediately  above 
the  transverse  fibres  of  the  corpus  callosum,  q.  In  front,  a,  they  bend 
downwards  within  the  gyrus  to  which  they  belong,  and  are  con- 
nected with  the  anterior  perforated  space,  being  joined  by  certain 
longitudinal  fibres,  which  run  along  the  under  surface  of  the  corpus 
callosum  near  the  middle  line,  passing  near  and  upon  the  upper  edge 
of  the  septum  lucidum.  Behind,  a c,  they  turn  round  the  back  of  the 
corpus  callosum  and  descend  to  the  point  of  the  middle  lobe,  a", 
where,  according  to  Foville,  jhey  again  reach  the  perforated  space. 
Ofisets,  c c c,  from  these  fibres  pass  upwards  and  backw'ards  into  the 
secondary  convolutions  in  the  longitudinal  fissure  derived  from  the 
gyrus  fornicatus. 

f.  Fasciculus  uncinatus. — Under  this  name  is  described  a white 
bundle,  fig.  344,  e,  seen  on  the  lateral  aspect  of  the  hemisphere,  pass- 
ing across  the  bottom  of  the  Sylvian  fissure,  and  connecting  the  ante- 


Fig.  345. 


Dissection  of  fibres  of  gyrus  fornicatus,  and  of  fornix.  (From  Foville,  slightly  altered.)  a.  An- 
terior, B.  Posterior  lobe,  a a!  a'\  Fibres  of  gyrus  fornicatus.  c.  Of  its  accessory  gyri.  b.  Tegmen- 
tum ; and  g.  crust — the  two  separated  by  locus  niger.  L The  thalamus,  n.  Corpus  albicans,  q. 
Corpus  callosum,  r.  Radiating  fibres  of  hemisphere,  s.  Septum  lucidum.  t.  fornix,  f.  Anterior 
pillar.  * Commencement  in  thalamus.  1.  Olfactory  nerve.  2.  Optic  commissure. 

rior  with  the  middle  and  posterior  lobes.  The  fibres  of  this  bundle 
expand  at  each  extremity,  and  the  superficial  portion  of  them  curve 


INTERNAL  STRUCTURE  OF  CEREBRUM. 


241 


or  hook  sharply  between  the  contiguous  parts  of  the  anterior  and 
middle  lobes, — whence  it  has  received  its  name. 

g.  The  convolutions  of  the  cerebrum  are  connected  with  each  other 
by  white  fibres,  which  lie  immediately  beneath  the  cortical  substance. 
Some  of  them,  fig.  344,  v,  pass  across  the  bottom  of  a sulcus  between 
adjacent  convolutions;  whilst  others,  which  are  long  and  run  deeper, 
connect  convolutions  situated  at  a greater  distance  from  one  another. 

The  central  part  of  the  white  substance  of  each  convolution  is 
formed  by  fibres  having  a different  origin;  some,  fig.  338,  being 
derived  from  the  radiating  peduncular  fibres,  and,  according  to  most 
anatomists,  others  from  the  transverse  fibres  of  the  corpus  callosum. 

The  researches  of  Foville  have  led  him  to  differ  considerably  from  other 
anatomists,  as  to  the  course  of  the  fibres  of  the  cerebrum,  as  wdl  be  seen  from 
the  following  statement  of  his  views : — 

1.  The  crust,  or  fasciculated  portion  of  each  cerebral  peduncle,  derived  from  the 
anterior  pyramid,  forms  by  itself  the  peduncular  fibrous  cone,  and  is  thence  con- 
tinued on  into  the  radiating  fibres  of  the  cerebrum,  which  are  destined  only  for 
the  convolutions  on  the  convex  surface  of  the  hemisphere,  including  the  outer 
half  of  the  marginal  convolution  of  the  longitudinal  fissure,  and  the  inner  half  of 
the  convolution  of  the  Sylvian  fissure. 

2.  The  fibres  of  the  tegmentum,  having  entered  the  thalamus,  pass  on  in  two 
ways — no  part  of  them,  be  it  observed,  joining  the  radiating  peduncular  fibres. 

a.  One  set  pass  upwards  through  the  thalamus  and  corpus  striatum,  above 
which  they  turn  inwards,  and,  joining  with  those  of  the  opposite  side,  form  the 
transverse  fibres  of  the  corpus  callosum.  ThS  corpus  callosum  is  therefore  re- 
garded as  a commissure  of  the  cerebral  peduncles  only — none  of  its  cross  fibres 
spreading  into  the  convolutions,  as  is  generally  believed. 

h.  The  second  set  of  fibres  of  the  tegmentum,  corresponding  with  the  fasciculi 
teretes  and  part  of  the  posterior  pyramids,  run  forwards  near  the  middle  line, 
along  the  under  side  of  the  third  ventricle  and  corpus  striatum,  through  the  gray 
matter  in  front  of  the  pons,  to  the  anterior  perforated  space.  The  remaining  part 
of  the  posterior  pyramid  forms  the  taenia  semicircularis,  which,  passing  down  in 
front  of  the  anterior  pillar  of  the  fornix,  also  reaches  the  perforated  space.  From 
this  space  more  fibres  are  reflected  upwards  on  the  sides  of  the  corpus  striatum 
to  join  the  corpus  callosum. 

3.  As  dependencies  of  the  posterior  peduncular  fibres,  and  connected  with  them 
at  the  borders  of  the  anterior  perforated  space,  are  : — 

a.  Several  sets  of  longitudinal  arched  fibres,  which  embrace,  in  a series  of 
rings,  the  radiating  peduncular  system.  These  are — the  deep  fibres  of  the  taenia 
semicircularis — a somewhat  similar  band  beneath  the  outer  part  of  the  corpus 
striatum — ^the  half  of  the  fornix  with  the  corpus  fimbriatum — the  longitudinal 
fibres  placed  on  the  upper  and  under  surface  of  the  corpus  callosum,  and  those  of 
the  septum  lucidum ; and,  lastly,  two  remarkable  systems  of  longitudinal  fibres — 
one  constituting  the  entire  white  substance  of  the  gyrus  fornicatus  (from  end  to 
end),  also,  of  its  accessory  convolutions,  and  of  the  inner  half  of  the  marginal 
convolution  of  the  longitudinal  fissure ; and  the  other,  forming  the  white  sub- 
stance of  the  convolutions  of  the  island  of  Red,  and  the  adjoining  half  of  the 
convolution  of  the  Sylvian  fissure.  None  of  the  parts  just  named  receive  fibres 
from  the  radiating  peduncular  set. 

h.  In  connexion  with  this  system  is  a thin  stratum  of  white  fibres,  found  upon 
the  internal  surface  of  the  ventricles,  and  prolonged  through  the  transverse  fissure 
into  the  reticulated  white  substance  covering  the  lower  end  of  the  gyrus  forni- 
catus; whence,  according  to  Foville,  it  extends,  as  an  exceedingly  thin  layer  of 
medullary  matter,  all  over  the  cortical  substance  of  the  hemisphere. 

c.  The  anterior  commissure  does  not  reach  the  convolutions,  but  radiates  upon 
the  outer  sides  of  the  corpora  striata  and  thalami. 

Gray  matter  of  the  encephalon. — Considering  the  imputed  physio- 
logical importance  of  the  gray  nervous  substance,  it  may  be  well  to 
VOL.  II.  21 


242 


ORIGINS  OF  CRANIAL  NERVES. 


mention  connectedly  the  different  positions  in  which  it  is  found  in  the 
several  parts  of  the  encephalon. 

By  far  the  larger  amount  is  situated  upon  the  convoluted  surface  of 
the  cerebrum  and  the  laminated  surface  of  the  cerebellum,  forming  in 
each  case  the  external  cortical  layer  of  cineritious  matter. 

In  the  middle  part  of  the  base  of  the  brain  it  is  seen  to  be  accumu- 
lated along  the  under  side  of  the  third  ventricle,  in  a layer  of  varying 
thickness,  extending  from  a little  above  the  optic  commissure  to  the 
back  part  of  the  interpeduncular  space,  forming  the  lamina  cinereo, 
the  tuber  cinereum,  and  the  gray  matter  in  the  posterior  perforated 
space,  the  infundibulum  and  pituitary  body  being  continuous  with  it 
below.  Towards  each  side,  in  front,  the  lamina  cinerea  is  connected 
with  the  gray  matter  of  the  anterior  perforated  space,  whence  a con- 
tinuity of  the  cineritious  substance  may  be  traced  forwards  into  the 
olfactory  nerve,  as  far  as  its  obtuse  extremity,  the  olfactory  lobe. 
Moreover,  this  median  stratum  of  gray  matter  seen  on  the  floor  of  the 
third  ventricle  is  prolonged  upwards  on  the  sides  of  the  thalami,  passes 
across  as  the  soft  commissure,  partly  surrounds  the  anterior  pillar  of 
the  fornix,  (having  entered  below  into  the  interior  of  the  corpus  albi- 
cans,) and  is  extended  higher  up  on  the  sides  of  the  septum  lucidum. 
In  the  crura  cerebri,  the  gray  matter  is  collected  into  a dark  mass, 
the  locus  niger,  and  is  also  diffused  among  the  fasciculi  of  the  teg- 
mentum ; below  this  it  is  confinuous  with  that  of  the  pons  and  medulla 
oblongata,  and  through  them  with  that  of  the  spinal  cord,  as  has 
already  been  sufficiently  described. 

In  the  centre  of  each  of  the  corpora  quadrigemina,  gray  matter  is 
also  found,  and  it  occurs  in  the  pineal  gland,  and  in  the  corpora  geni- 
culata.  These  last  bodies  appear  to  be  appendages  of  the  large 
masses  of  gray  matter  situated  in  the  interior  of  the  cerebrum,  named 
the  optic  thalami;  which  again  are  succeeded  by  the  still  larger  col- 
lections of  this  substance,  and  indeed  the  largest  situated  within  the 
brain,  viz.,  the  corpora  striata.  The  gray  matter  of  each  corpus 
striatum  is  continuous  below  with  that  of  the  anterior  perforated 
space;  and  on  its  outer  side,  is  the  thin  layer  of  gray  matter  named 
the  claustrum,  the  connexions  of  which  are  not  well  understood. 

In  the  centre  of  each  hemisphere  of  the  cerebellum  is  the  corpus 
dentatum. 

CONNEXIONS  OF  THE  CKANIAL  NERVES  WITH  THE  ENCEPHALON. 

The  cranial  nerves  arise  from  the  under  part  of  the  brain  and  issue 
through  the  foramina  in  the  base  of  the  skull.  They  are  usually 
reckoned  as  forming  nine  pairs  (see  fig.  331,  where  they  are  num- 
bered ^ to  ®).  The  several  designations  of  these  nerves  as  well  as  their 
course  within  the  cranium  will  be  subsequently  described.  It  is  here 
proposed  to  give  an  account  of  their  connexions  with  the  encephalon, 
or  what  is  usually  called  their  root  or  origin. 

The  roots  of  the  nerves  may  be  traced  for  some  depth  into  the  sub- 
stance of  the  encephalon,  a circumstance  which  has  led  to  the  dis- 
tinction of  the  deep  or  real  origin,  and  the  superficial  or  apparent 


ORIGINS  OF  CRANIAL  NERVES. 


243 


origin,  by  which  latter  is  understood  the  place  at  which  the  nerve 
appears  attached  to  the  surface  of  the  encephalon.  The  superficial 
origin  of  these  nerves  is  quite  obvious,  but  tlieir  deeper  connexion  is, 
in  most  cases,  a matter  of  much  uncertainty.  For  this  reason  the 
apparent  origin  is  described  before  the  deep  origin,  which  is  less  per- 
fectly known. 

1.  The  first  or  olfactory  nerve,  figs.  331,  332,  % small  in  man  in  com- 
parison with  lower  animals,  lies  on  the  under  surface  of  the  anterior 
lobe  to  the  outer  side  of  the  longitudinal  median  fissure,  lodged  in  a 
sulcus  between  two  straight  convolutions.  Unlike  other  nerves,  it 
consists  of  a large  proportion  of  gray  matter  mixed  wfith  white  fibres, 
and,  indeed,  is  rather  to  be  considered  a prolongation  of  the  anterior 
lobe.  It  enlarges  into  a bulb,  olfactory  bulb,  in  front,  which  also  con- 
tains much  gray  matter,  and  from  this  part  small  soft  nerves  descend 
through  the  cribriform  plate  of  the  skull  into  the  nose.  On  turning 
back  the  bulb,  it  is  seen  that  the  nerve  behind  that  part  is  three-sided, 
its  upper/edge  lying  in  the  groove  or  sulcus  above-mentioned.  When 
traced  backwards,  it  is  found  to  be  spread  out  and  attached  behind  to 
the  under  surface  of  the  anterior  lobe  by  means  of  three  portions  or 
roots,  named  external,  middle,  and  internal,  which  pass  in  diflerent 
directions. 

The  exterval  or  long  root  consists  of  a band  of  medullary  fibres, 
which  passes,  in, the  form  of  a white  streak,  outwards  and  backwards 
along  the  anterior  margin  of  the  perforated  space,  towards  the  poste- 
rior border  of  the  Sylvian  fissure,  where  it  may  be  followed  into  the 
substance  of  the  cerebrum.  Its  further  connexions  are  doubtful,  but  it 
has  been  stated  that  its  fibres  have  been  traced  to  ihe  following  parts, 
viz.,  the  convolutions  of  the  island  of  Reil,  the  anterior  commissure, 
and  the  superficial  layer  of  the  optic  thalamus  (Valentin). 

The  middle  or  gray  root  is  of  a pyramidal  shape,  and  consists  of 
gray  matter  on  the  surface,  which  is  prolonged  from  the  adjacent  part 
of  the  anterior  lobe  and  perforated  space.  Within  it  there  are  white 
fibres,  which  have  been  trac.ed  to  the  corpus  striatum. 

The  internal  root  {short  root,  Scarpa),  which  cannot  always  be 
demonstrated,  is  composed  of  white  fibres  which  may  be  traced  from 
the  inner  and  posterior  part  of  the  anterior  lobe,  where  they  are  said 
by  Foville  to  be  connected  with  the  longitudinal  fibres  of  the  gyrus 
fornicatus. 

[The  following  observations  upon  the  connexions  and  structure  of  the  olfactory 
bulb  and  pedicle  were  made  upon  several  human  brains  a few  hours  after  death, 
and  may  not  prove  uninteresting  as  a point  of  special  anatomy. 

The  olfactory  pedicle  or  commissure  is  triangular,  its  apex  and  two  sides  being 
received  into  a fissure  of  the  anterior  inferior  part  of  the  marginal  convolution 
of  the  longitudinal  fissure,  and  its  base  being  inferior.  Postero-superiorly  it  forms 
a large  round  prominence  (fig.  347,  A,  c),  externally  composed  of  ganglionary 
substance,  around  the  base  of  which  the  locus  perforatus  (fig.  347,  B,  c)  is  con- 
tinuous. 

The  pedicle  is  composed  of  several  distinct  commissural  bands. 

The  first  or  most  external  commissural  band  (fig.  346.  a,  fig.  347,  B,  a)  of  the 
olfactory  bulb,  or  external  root  of  the  olfactory  nerve,  as  it  is  improperly  called,  is 
composed  of  nerve-fibres,  and  curves  from  the  outer  part  of  the  fissura  Sylvii,  at 


244 


CONNEXIONS  OF  THE  CRANIAL  NERVES 


[Fig.  346. 


»5.  u-iLf  icjMcaciHs  uii  imtiiur  view  ui  me  rigm  oiraciory  ganglion  ana  commissure,  a.  cjx- 
ternal  commissurul  band.  d.  Internal  commissural  band. — J.  L.] 

the  exterior  boundary  of  the  locus  perforatus,  inwards  and  forwards.  It  forms 

two  thirds  of  the  external,  and  a narrow 
[Fig.  347.  line  of  the  inferior  surface  of  the  pedicle, 

and  when  it  reaches  the  bulb,  divides 
into  two  branches,  which  join  the  gan- 
glionary substance  of  the  latter.  The 
most  external  of  the  two  branches  can 
be  traced  farthest  into  the  bulb. 

The  internal  commissural  band  (fig. 
346  d;  fig.  347,  A,  a,)  emerging  from 
the  locus  perforatus,  is  also  composed 
nerve-fibres,  and  running  forwards 
forms  the  infero-internal  boundary  of 
^ the  pedicle,  and  terminates  in  the  bulb 

Fig.  347.  A,  represents  the  appeamnce  of  the  by  dividing  into  three  branches. 

internal  face  of  the  olfactory  pedicle  of  the  left  The  external  and  internal  commis- 

side.  o.  Internal  commissural  band.  6.  Superior  gural  bands  are  separated  from  each 

other  by  a fissure  running  along  the 
ollactory  pedicle,  a.  Lscape  ol  a white  hbre  . ^ ^ 

from  the  gray  substance  going  to  join  the  white  iniorior  surface  ol  the  pedicle,  and  are 

band.  held  in  close  apposition  by  an  envelope 

B,  represents  the  appearance  of  the  external  of  pia  mater.  When  the  latter  is  laid 
surface  of  the  olfactory  pedicle  of  the  lelt  side,  open  and  the  bands  pressed  apart,  the 
a tiXlernal  commissural  band  loined  by  wime  r-  i-  i t 

fibres  escaping  from  the  superior  gray  band  (A)  fissure  disappears,  and  he  two  bands 
c.  Conlinnation  of  the  loeus  perforatus  around  presented  as  a Single  white  layer, 
the  protuberant  base  of  the  olfactory  pedicle. — about  two  lines  in  width,  and  forming 
From  nature,  by  J.  L.]  the  inferior  part  of  the  olfactory  pedicle. 

The  middle  or  superior  commissural 
band  (fig.  347,  A,  B,  b),  forming  the  superior  part  of  the  olfactory  pedicle, 
consists  of  ganglionary  substance  continuous  with  that  of  the  locus  perforatus  and 
the  olfactory  bulb.  At  the  posterior  part  of  this  band,  upon  each  side,  but  espe- 
cially the  external  one  (fig.  347,  B),  white  fibres  are  frequently  found  escaping 
from  the  gray  substance,  and  running  forwards  with  an  inclination  downwards,  to 
join  the  white  commissural  bands. 

At  the  conjunction  of  the  commissural  bands  within  the  olfactory  bulb,  a small 
fissure  or  cavity  is  left  lined  with  a delicate  epithelium. 

The  olfactory  bulb  or  ganglion,  is  composed  of  an  intermixture  of  ganglionary 
corpuscles  and  nerve-fibres,  and  from  its  inferior  surface  the  olfactory  nerves 
originate.  In  the  pia  mater  covering  it,  in  the  negro,  I have  frequently  observed 
a deposit  of  pigment  cells. — J.  L.] 

2.  The  second  pair  of  nerves,  or  the  optic  nerves,  ^ of  the  two  sides, 
meet  each  other  at  the  optic  commissure  (chiasma),  c,  where  they 
partially  decussate.  From  this  point  they  may  be  traced  backwards 
around  the  crura  cerebri  under  the  name  of  the  optic  tracts. 

Each  optic  tract,  u,  arises  from  the  optic  thalamus,  the  corpora 
quadrigemina,  and  the  corpora  geniculata.  As  it  leaves  the  under 


WITH  THE  encephalon. 


245 


part  of  the  thalamus,  it  makes  a sudden  bend  forwards  and  then  runs 
obliquely  across  the  under  surface  of  the  cerebral  peduncle,  fig.  348, 
in  form  of  a flattened  band,  which  is  attached  by  its  anterior  edge  to 
the  peduncle;  after  this,  becoming  cylindrical,  it  adheres  to  the  tuber 
cinereum,  from  which  and,  as  was  first  pointed  out  by  Vicq-d’Azyr,* 
from  the  lamina  cinerea  it  is  said  to  receive  an  accession  of  fibres,  and 
thus  reaches  the  optic  commissure. 

In  the  commissure  the  nerves  of  the  two  sides  undergo  a partial  de- 
cussation. The  outer  fibres  of  each  tract  continue  on  to  the  eye  of  the 
same  side;  the  inner  fibres  cross  over  to  the  opposite  side;  and  fibres 
have  been  described  as  running  from  one  optic  tract  to  another  along  the 
posterior  part  of  the  commissure,  and  others  between  the  two  optic 
nerves  in  its  anterior  part  (Mayo). 

In  front  of  the  commissure,  the  nerves  enter  the  foramen  opticum, 
receiving  a sheath  from  the  dura  mater  and  acquiring  greater 
firmness. 

The  fibres  of  origin  of  the  optic  tract  from  the  thalamus  are  derived  partly  from 
the  superficial  stratum,  and  partly  from  the  interior  of  that  body.  According  to 
Foville,  this  tract  is  also  connected  with  the  taenia  semicircularis,  and  with  the 
termination  of  the  gyrus  fornicatus;  and  he  states  further,  that  where  the  optic 
tract  turns  round  the  back  of  the  thalamus  and  the  cerebral  peduncle,  it  receives 
other  delicate  fibres,  which  descend  from  the  gray  matter  of  those  parts. — (Op. 
cit.  p.  514.) 

3.  The  third  pair  oh  nerves,  ^ (motores  oculorum,)  have  their  appa- 
rent or  superficial  origin  from  the  inner  surface  of  the  crura  cerebri 
in  the  interpeduncular  space,  immediately  before  the  pons,  fig.  348,®. 
Each  nerve  consists  of  a number  of  funiculi  which  arise  in  an  oblique 
line  from  the  surface. 

As  to  their  deep  connexions, — the  fibres  of  origin  are  found  to 
diverge  in  the  substance  of  the  crus,  some  being  traced  to  the  locus 
niger,  others  running  downwards  in  the  pons  amongst  its  longitudinal 
fibres,  and  others,  again,  turning  upwards  to  be  connected  with  the 
corpora  quadrigemina  and  Vieussenian  valve. 

4.  The  fourth  pair,  pathetic  or  trochlear  nerves,  figs.  331 , 348,  ^ the 
smallest  of  those  which  are  derived  from  the  brain,  are  seen  at  the 
outer  side  of  the  crura  cerebri  immediately  before  the  pons.  Each 
nerve  may  be  traced  backwards  round  the  peduncle  to  below  the  cor- 
pora quadrigemina,  where  it  arises  from  the  upper  part  of  the  valve 
of  Vieussens,  fig.  330.  The  roots  of  the  nerves  of  opposite  sides  are 
connected  together  across  the  middle  line,  in  the  form  of  a white  band 
or  commissure  in  the  substance  of  the  velum. 

5.  The  fifth  pair  of  nerves,  par  trigeminum,  trifacial  nerves.  The 
superficial  origin  of  these  nerves,  figs.  331,  348,  is  from  the  side 
of  the  pons  Varolii,  where  the  latter  is  connected  with  the  middle 
crus  cerebelli,  considerably  nearer  to  the  upper  than  to  the  lower 
border  of  the  pons. 

The  fifth  nerve  consists  of  a larger  or  sensory,  and  a smaller  or 
motor  root,  fig.  348.  The  smaller  root  is  at  first  concealed  by  the  larger, 
and  is  placed  a little  higher  up,  there  being  often  two  or  three  cross 

* Op.  cit.  p.  72,  pi.  xxi. 

21* 


21G 


CONNEXIONS  OF  THE  CRANIAL  NERVES 


fibres  of  the  pons  between  thenn.  On  separating  the  two  roots,  the 
0^0  lesser  one  is  seen  to  consist  of  a very 

few  iuniculi.  in  the  larger  root  the 
funiculi  are  numerous,  amounting 
sometimes  to  nearly  a hundred.  This 
2 root  acquires  its  neurilemma  sooner 
at  the  circumference  than  in  the  cen- 
tre, so  that  the  outward  cords  are 
longer  than  those  within,  and  when 
the  bunch  of  funiculi  is  pulled  away, 
a small  conical  eminemm  of  while 
substance  remains  behind. 

Deep  origin.  The  greater  root  runs 
beneath  the  transverse  fibres  of  the 
pons  towards  the  lateral  part  of  the 
medulfa  oblongata  behind  the  olivary 
body.  Several  anatomists  trace  it 
into  I he  floor  of  the  fourth  ventricle, 
between  the  fasciculi  teretes  and  the 
restiform  bodies.  some  it  is  con- 
sidered to  be  continuous  with  the 
fasciculi  teretes  and  lateral  columns 

^ . ...  of  the  cord,  whilst  others  connect  it 

I"  ront  view  of  crura  cerebri,  pons,  medulla  -.i  i i ■ i • i i 

obiongaia.  and  pari  of  spinal  cord  (Bell).  With  Hie  gray  mass  which  IS  regarded 
The  origins  of  some  of  the  cranial  nerves  py  Stilling  aS  the  nUcleUS  of  the  gloSSO- 
are  shown.  2.  Opiic  nerve.  3.  Motor  oculi.  i ^ 

4.  Pathetic  nerve.  5.  Fifth,  or  trifacial  nerve,  punryngeal  nerve. 

6.  Abdnceni  nerve.  7.  Andiiory  and  facial  The  motor  rOOt  was  SUppOSed  by 


a Eigbih  pair,  in-  descend  to  the  pyramidal 


nerves — sevenih  pair, 
eluding  glosso-pharyngeal,  vagus,  and  spinal 
accessory  nerves.  9 Hypoglossal  nerve,  bodv,  and  RetziuS  bcHeveS  that  he  hllS 
1.  A spinal  nerve.  c i .i  . • ■ u j- 

confirmed  that  opinion  by  dissection; 
but  the  deep  connexion  of  this  root  is  not  known  with  certainty. 


According  to  Foville,  some  of  the  fibres  of  the  sensory  root  of  the  fifth  nerve 
are  connected  with  transverse  fibres  in  the  pons,  whilst  others  spread  out  on  the 
surface  of  the  middle  peduncle  of  the  cerebellum,  and  enter  that  part  of  the  ence- 
phalon beneath  the  folia. — (Op.  cit.  p.  506.) 


6.  The  sixth  nerve  (abducens),  motor  oculi  externus,  figs.  331,  348, 
takes  its  apparent  origin  from  between  the  pyramidal  body  and  the 
pons  Varolii  by  means  of  a large  and  a smaller  bundle.  It  really 
arises  from  the  pyramid,  and  to  a small  extent  from  the  pons  also. 

7.  The  seventh  pair  of  nerves,  appear  on  each  side  at  the  poste- 
rior margin  of  the  pons,  opposite  its  junction  with  the  middle  peduncles 
of  the  cerebellum,  and  therefore  in  a line  with  the  place  of  attach- 
ment of  the  fifth  nerve.  The  seventh  nerve  is  divided  into  two  per- 
fectly distinct  portions,  which,  in  fact,  are  two  different  nerves:  the 
one,  named  the  portio  dura,  is  the  muscular  nerve  of  the  face;  the 
other,  or  portio  mollis,  is  the  nerve  of  hearing. 

The  portio  dura  or  facial  nerve,  placed  a litlle  nearer  to  the  mid- 
dle line  than  the  portio  mollis,  may  be  traced  to  the  medulla  oblongata 
between  the  restiform  and  olivary  fasciculi,  with  both  of  which  it  is 
said  to  be  connected.  Some  of  its  fibres  are  derived  from  the  pons. 


WITH  THE  ENCEPHALON. 


247 


Connected  with  the  portio  dura,  and  intermediate  between  it  and 
the  portio  mollis,  is  a smaller  white  i'uniculus,  first  described  by  Wris- 
berg  (portio  inter  duram  et  mollem).  The  roots  of  this  accessory 
portion  are  connected  deeply  with  the  lateral  column  of  the  cord. 

The  'portio  mollis,  figs.  331,  348,  ^ or  auditory  nerve,  rises  from  the 
floor  of  the  fourth  ventricle,  at  the  back  of  the  medulla  oblongata,  in 
which  situation,  as  already  described,  numerous  w'hite  striae  are  seen, 
which  form  the  commencement  of  the  nerve,  fig.  330.  These  roots 
are  connected  with  the  gray  matter,  and  some  appear  to  come  out  of 
the  median  fissure.  The  nerve  then  turns  round  the  restiform  body, 
and  becomes  applied  to  the  lower  border  of  the  pons,  receiving  acces- 
sions from  the  former  of  those  parts,  and  according  to  some  authori- 
ties from  the  latter  also. 

Foville  says  that  the  roots  of  the  portio  mollis  are  also  connected  by  a thin 
layer  on  the  under  surface  of  the  middle  peduncle  with  the  cortical  substance  of  the 
cerebellum ; also,  with  the  small  lobule  named  the  flocculus ; and  with  the  gray 
matter  at  the  borders  of  the  calamus  scriptorius. 

8.  The  eighth  pair,  figs.  331,  348,  * ®",  of  cranial  nerves  consists 

of  a series  of  funiculi  wdiich  arise  along  a lateral  line  from  the  medulla 
oblongata,  and  cervical  part  of  the  spinal  cord. 

The  uppermost  bundle  is  the  glosso-pharyngeal  nerve,  ®;  next  to 
this,  and  lower  down,  is  the  par  vagum  or  pnejimogastric  nerve, 
consisting  of  a larger  number  of  white  cords.  The  roots  of  both  these 
nerves  are  attached  superficially  to  the  fore  part  of  the  restiform  bf)dy. 
Still  lower,  is  the  spinal  accessory  nerve,®",  which  comes  up  from  the 
side  of  the  spinal  cord,  enters  the  skull  by  the  foramen  magnum,  and 
is  associated  with  the  vagus  nerve,  as  it  passes  out  through  the  fora- 
men lacerum. 

The  accessory  nerve  arises  within  the  spinal  canal  from  the  lateral 
column  of  the  cord,  near  the  posterior  lateral  fissure,  by  a series  of 
slender  roots,  which  commence  about  as  low'  down  as  the  sixth  cer- 
vical nerve.  The  nerve  passes  upwards  between  the  posterior  roots 
of  the  cervical  nerves  and  the  ligamentum  denticulatum, — its  several 
funiculi  of  origin  successively  joining  it  as  it  ascends.  On  entering 
the  skull,  it  receives  funiculi  from  the  side  of  the  medulla  oblongata. 

These  three  portions  of  the  eighth  pair  are  connected  deeply  with 
gray  nuclei  within  the  cord  and  medulla  oblongata,  as  already  fully 
described  (see  p.  232). 

9.  The  ninth  nerve,  figs.  331,  348,  (hj'poglossal,)  arises,  in  a line 
continuous  with  that  of  the  anterior  roots  of  the  spinal  nerves,  by 
scattered  funiculi  from  the  furrow  between  the  olivary  body  and  the 
anterior  pyramid. 

Its  roots  are  traced  by  Stilling  to  one  of  the  gray  nuclei  already 
described  in  the  medulla  oblongata. 

THE  MEMBRANES  OF  THE  BRAIN  AND  SPINAL  CORD. 

As  already  stated,  the  cerebro-spinal  axis  is  protected  by  three 
membranes,  named  also  meninges  (p-'^viyg).  They  are  : — 1.  An  external 
fibrous  membrane,  named  the  dura  mater,  which  closely  lines  the  inte- 
rior of  the  skull,  and  forms  a loose  sheath  in  the  spinal  canal ; 2.  An 


248 


THE  DURA  MATER. 


internal  cellulo-vascular  tunic,  the  pia  mater,  which  accurately  covers 
the  brain  and  spinal  cord;  and  3.  An  intermediate  serous  sac,  the 
arachnoid  membrane,  which,  by  its  parietal  and  visceral  layers,  covers 
the  internal  surface  of  the  dura  mater  on  the  one  hand,  and  is  reflected 
over  the  pia  mater  on  the  other. 

THE  DURA  MATER. 

The  dura  mater,  a very  strong,  dense,  inelastic,  fibrous  tunic,  of  con- 
siderable thickness,  is  closely  lined  on  its  inner  surface  by  the  outer 
portion  of  the  arachnoid,  and  with  it,  therefore,  forms  a Jibro-serous 
membrane,  which  is  free,  smooth,  and  epitheliated  on  its  inner  surface, 
where  it  is  turned  towards  the  brain  and  cord,  but  which,  by  its  outer 
surface,  is  connected  in  a difierent  manner  in  the  cranium,  and  in  the 
spinal  canal. 

The  outer  surface  of  the  cranial  portion  adheres  to  the  inner  surface 
of  the  bones,  and  forms  their  internal  periosteum.  The  connexion  be- 
tween the  two,  in  a great  measure,  depends  on  blood-vessels  and  small 
fibrous  processes,  which  pass  from  one  to  the  other;  and  the  dura 
mater,  when  detached  and  allowed  to  float  in  water,  presents  a floc- 
culent  appearance  on  its  outer  surface,  in  consequence  of  the  torn  parts 
projecting  from  it. 

The  adhesion  between  the  membrane  and  the  bone  is  more  intimate 
opposite  the  sutures,  and  also  generally  at  the  base  of  the  skull,  wliich 
is  uneven,  and  perforated  by  numerous  foramina,  through  which  the 
dura  mater  is  prolonged  to  the  outer  surface,  being  there  continuous 
with  the  pericranium.  The  fibrous  tissue  of  the  dura  mater  becomes 
blended  with  the  cellular  sheaths  of  the  nerves,  at  the  foramina  which 
give  issue  to  them. 

In  leaving  the  skull,  the  dura  mater  is  intimately  attached  to  the 
margin  of  the  foramen  magnum  ; but  within  the  vertebral  canal  it 
forms  a loose  sheath  around  the  cord,  {theca,)  and  is  not  adherent  to 
the  bones,  which  have  an  independent  periosteum.  Towards  the  lower 
end  of  the  canal  a few  fibrous  slips  proceed  from  the  outer  surface  of 
the  dura  mater  to  be  fixed  to  the  vertebras.  The  space  intervening 
between  the  canal  and  the  dura  mater  is  occupied  by  loose  fat,  by 
watery  cellular  tissue,  and  by  a plexus  of  spinal  veins. 

Opposite  each  intervertebral  foramen  the  dura  mater  presents  two 
openings,  placed  side  by  side,  which  give  passage  to  the  two  roots  of 
the  corresponding  spinal  nerve.  It  is  continued  as  a tubular  prolon- 
gation on  the  nerve,  and  is  lost  upon  its  sheath.  Besides  this,  it  is 
connected  with  the  circumference  of  the  foramen  by  cellular  tissue. 

The  fibrous  tissue  of  the  dura  mater,  especially  within  the  skull,  is 
divisible  into  two  distinct  layers,  and  at  various  places  these  layers 
separate  from  each  other  and  leave  intervening  channels,  called  sinuses. 
These  sinuses,  which  have  been  elsewhere  described,  are  canals  lor 
venous  blood,  and  are  lined  with  a continuation  of  the  internal  mem- 
brane of  the  veins. 

The  dura  mater  also  sends  inwards  into  the  cavity  of  the  skull  three 
strong  membranous  processes,  or  partitions,  which  are  regarded  as 
duplicatures  of  its  inner  layer.  Of  these,  one  descends  vertically  in 


THE  DURA  MATER. 


249 


the  median  plane,  and  is  received  into  the  longitudinal  fissure  between 
the  two  hemispheres  of  the  cerebrum.  This  is  ihe  falx  cerebri.  The 
second  is  an  arched  or  vaulted  partition,  stretched  across  the  back 
part  of  the  skull,  between  the  cerebrum  and  the  cerebellum  : it  is  named 
the  tentorium  cerebelli.  Below  this,  another  vertical  partition,  named 
falx  cerebelli,  of  small  extent,  passes  down  between  the  hemispheres  of 
the  cerebellum. 

The  falx  cerebri  is  narrow  in  front,  where  it  is  fixed  to  the  crista 
gain,  and  broader  behind,  where  it  is  attached  to  the  middle  of  the 
upper  surface  of  the  tentorium,  along  which  line  of  attachment  the 
straight  sinus  is  situated.  Along  its  upper  convex  border,  which  is 
attached  above  to  the  middle  line  of  the  inner  surface  of  the  cranium, 
runs  the  superior  longitudinal  sinus.  Its  under  edge  is  free,  and 
reaches  to  within  a short  distance  of  the  corpus  callosum,  approaching 
nearer  to  it  behind.  This  border  contains  the  inferior  longitudinal 
sinus. 

The  tentorium,  nr  tent,  is  elevated  in  the  middle,  and  declines  down- 
wards in  all  directions  towards  its  circumference,  in  correspondence 
with  the  upper  surface  of  the  cerebellum.  Its  inner  border  is  free  and 
concave,  and  leaves  in  front  of  it  an  oval  opening,  through  which  the 
isthmus  encephali  descends.  It  is  attached  behind  and  at  the  sides  by 
its  convex  border  to  the  horizontal  part  of  the  crucial  ridges  of  the  occi- 
pital bone,  and  there  encloses  the  lateral  sinuses.  Further  forward  it 
is  connected  with  the  upper  edge  of  the  petrous  portion  of  the  temporal 
bone — the  superior  petrosal  sinus  running  along  this  line  of  attachment. 
At  the  point  of  the  pars  petrosa,  the  external  and  internal  borders  meet, 
and  may  be  said  to  intersect  each  other — the  former  being  then  con- 
tinued inwards  to  the  posterior,  and  the  latter  forwards  to  the  anterior 
clinoid  process. 

The /i//:c  cerebelli  (falx  minor)  descends  from  the  middle  of  the  pos- 
terior border  of  the  tentorium,  with  which  it  is  connected,  along  the 
vertical  ridge  named  the  internal  occipital  crest,  towards  the  foramen 
magnum,  bifurcating  there  into  two  smaller  folds.  Its  attachment  to 
the  bony  ridge  marks  the  course  of  the  posterior  occipital  sinus,  or 
sinuses. 

Structure. — The  dura  mater  consists  of  white  fibrous  tissue,  arranged 
in  bands  and  lanunm,  crossing  each  other.  It  is  traversed  by  numerous 
blood-vessels  which  are  destined  for  the  bones.  Minute  nervous  fila- 
ments, derived  from  the  fourth  and  fifth  cranial  nerves,  and,  according 
to  some  anatomists,  from  the  sympathetic,  are  described  as  entering 
the  dura  mater. 

Glandules  Pacchioni. — Upon  the  external  surface  of  the  dura  mater, 
in  the  vicinity  of  the  longitudinal  sinus,  are  seen  numerous  small  granu- 
lar-looking elevations,  generally  collected  into  clusters,  named  glands  of 
Pacchioni.  The  inner  surface  of  the  calvarium  is  marked  by  little 
pits,  which  receive  these  eminences.  Similar  excrescences  are  seen 
on  the  internal  surface  of  the  dura  mater,  and  also  upon  the  pia  mater 
on  each  side  of  the  longitudinal  sinus:  moreover,  some  project  into  that 
sinus  itself. 

It  seems  probable  that  these  small  bodies  are  originally  developed 


250 


THE  PIA  MATER. 


from  the  pia  mater,  and  extend  themselves  through  the  dura  mater  to 
the  external  surface,  causing  a partial  absorption  or  separation  of  the 
fibres  of  that  membrane.  In  like  manner,  those  seen  in  the  longitudinal 
sinus  seem  to  have  perforated  the  dura  mater,  carrying  before  them  a 
covering  of  the  venous  lining  membrane.  They  consist,  according  to 
Valentin,  of  exudation  corpuscles,  and,  in  an  older  or  more  advanced 
condition,  are  composed  of  fibres.  The  cerebral  layer  of  the  arachnoid 
in  the  neighbourhood  of  these  growths  is  usually  thickened  and  opaque, 
and  often  adheres  to  the  parietal  portion. 

These  bodies  are  not  found  at  birth;  and  according  to  the  brothers 
Wenzel,  exist  in  very  small  number,  if  at  all,  under  the  third  year. 
Beyond  the  seventh  year  they  are  usually  found,  and  they  increase  in 
number  greatly  as  life  advances;  in  some  cases,  however,  they  are 
altogether  wanting.  In  animals  there  appears  to  be  no  corresponding 
structure. 

Similar  bodies  are  often  found  attached  to  the  choroid  plexuses  of 
the  fourth  ventricle. 

From  all  the  circumstances  of  their  history,  these  so-called  glands 
of  Pacchioni  have  been  regarded  by  many  as  the  result  of  a chronic 
action,  producing  an  unnatural  deposit  in  this  situation.  They  are 
certainly  not  glandular  in  their  nature. 

THE  PIA  MATER. 

The  pia  mater  is  a delicate  cellulo-vascular  membrane,  richly 
supplied  with  vessels,  which  immediately  invests  the  brain  and  spinal 
cord. 

Upon  the  hemispheres  of  the  brain,  it  is  applied  to  the  entire  cortical 
surface  of  the  convolutions,  and  dips  into  all  the  sulci.  From  its  in- 
ternal surface  a multitude  of  small  vessels  enter  the  gray  matter,  and 
extend  for  some  distance  perpendicularly  into  the  substance  of  the 
brain.  This  inner  surface  of  the  cerebral  pia  mater  is  on  this  account 
very  flocculent,  and  is  named  tomentum  cerehri.  On  the  cerebellum 
a similar  arrangement  exists,  but  the  membrane  is  finer  and  the  vessels 
from  its  inner  surface  are  not  so  long.  The  pia  mater  is  also  prolonged 
into  the  ventricles,  and  there  forms  the  velum  interpositum  and  choroid 
plexuses. 

Structure. — It  consists  of  interlaced  bundles  of  cellular  tissue,  con- 
veying great  numbers  of  blood-vessels ; and,  indeed,  its  peculiar  office, 
both  on  the  brain  and  spinal  cord,  seems  to  be  that  of  providing  a nidus 
or  matrix  for  the  support  of  the  blood-vessels,  as  these  are  subdivided 
before  they  enter  the  nervous  substance.  According  to  Fohmann  and 
Arnold  it  contains  numerous  lymphatic  vessels. 

On  the  spinal  cord  the  pia  mater  has  a very  different  structure  from 
that  which  it  presents  on  the  encephalon,  so  that  it  has  even  been 
described  by  some  as  a diflbrenl  membrane  under  the  name  neurilemwa 
of  the  cord.  It  is  thicker,  firmer,  less  vascular,  and  more  adherent  to 
the  subjacent  nervous  matter  : its  greater  strength  is  owing  to  its  con- 
taining fibrous  tissue,  which  is  arranged  in  longitudinal  shining  bundles. 
A process  of  this  membrane  dips  down  into  the  anterior  fissure  of  the 
cord,  and  serves  to  conduct  blood-vessels  into  that  part.  At  the  roots 


THE  ARACHNOID  MEMBRANE. 


251 


of  the  nerves,  both  in  the  spine  and  in  the  cranium,  the  pia  mater 
becomes  continuous  with  their  neurilemma. 

Towards  the  upper  part  of  the  cord,  the  pia  mater  presents  a grayish 
mottled  appearance,  which  is  owing  to  pigment  particles  deposited 
within  its  tissue. 

THE  ARACHNOID  MEMBRANE. 

The  arachnoid  is  a very  fine,  delicate,  serous  membrane,  which,  like 
other  membranes  of  that  class,  forms  a shut  sac  and  consists  of  two 
portions,  viz.,  a visceral  (or  cerebral)  and  a parietal  layer. 

The  parietal  layer,  as  already  said,  adheres  to  the  dura  mater  of 
the  brain  and  spinal  cord, — the  adhesion  of  one  membrane  to  the 
other  being  most  intimate. 

The  visceral  portion  passes  over  the  various  eminences  and  depres- 
sions on  the  cerebrum  and  cerebellum,  without  dipping  into  the  sulci 
and  smaller  fissures;  nor  is  it  uniformly  and  closely  adherent  to  the 
pia  mater.  The  interval  left  between  these  two  membranes  is  named 
generally  the  subarachnoid  space. 

This  subarachnoid  space  is  wider  and  more  evident  in  some  posi- 
tions than  in  others.  Thus, — in  the  longitudinal  fissure,  the  arachnoid 
does  not  descend  to  the  bottom,  but  passes  across,  immediately  below 
the  edge  of  the  falx,  at  a little  distance  above  the  corpus  callo.«um. 
In  the  interval  thus  left,  the  arteries  of  the  corpus  callosum  run  back- 
wards along  that  body.  At  the  base  of  the  brain  and  in  the  spinal 
canal  there  is  a wide  interval  between  the  arachnoid  and  the  pia 
mater.  In  the  former  situation,  this  subarachnoid  space  extends  over 
the  pons  and  the  interpeduncular  space  as  far  forwards  as  the  optic 
nerves : around  the  cord,  this  space  is  also  of  considerable  extent. 

A certain  quantity  fluid  is  contained  within  the  proper  sac  of  the 
arachnoid  ; but  it  has  been  showm  by  Magendie  that  the  chief  part  of 
the  cerebro-spinal  fluid  is  lodged  under  the  arachnoid,  in  the  subarach- 
noid space,  which  usually  communicates  by  an  opening  at  the  point  of 
the  fourth  ventricle  with  the  general  ventricular  cavity,  as  elsewhere 
stated.  (Fig.  332,  z.) 

Magendie  also  pointed  out  the  existence  of  a sort  of  septum  dividing 
the  spinal  subarachnoid  space  at  the  back  of  the  cord.  This  is  a thin 
membranous  partition,  which  passes  in  the  median  plane  from  the  pia 
mater  covering  the  posterior  median  fissure  of  the  cord  to  the  opposite 
part  of  the  loose  portion  of  the  arachnoid  membrane.  It  is  incomplete 
and  cribriform;  and  consists  of  bundles  of  white  fibres  interlaced  more 
or  less  with  one  another.  Fibrous  bands  of  the  same  texture  pass 
across  the  subarachnoid  space  in  various  situations  both  within  the 
spinal  canal  and  at  the  base  of  the  brain,  stretching  thus  from  the 
arachnoid  to  the  pia  mater.* 

* I was  at  one  time  disposed  to  think  that  the  subarachnoid  space  was  lined  throug^hout 
by  a delicate  serous  membrane,  and  that  the  septum  above  described  consisted  of  a dupli- 
cature  of  this  membrane,  e.xtending  from  the  loose  arachnoid  to  the  cord,  as  the  mesentery 
passes  to  the  intestine.  I was  led  to  entertain  this  idea,  on  considering  that  the  space  in 
question  contains  fluid  ; that  the  loose  portion  of  the  arachnoid  is  separable,  in  many 
parts,  into  two  layers  ; and  that  a thin  membrane  can  be  raised  from  the  surface  of  the 
ligamentum  denticulatum  and  the  roots  of  the  nerves,  as  they  pass  across  the  space.  I 


252 


THE  ARACHNOID  MEMBRANE. 


As  the  cerebral  and  spina!  nerves  proceed  to  their  foramina  of  exit 
from  the  cranium  and  vertebral  canal,  they  are  loosely  surrounded  by 
tubular  sheaths  of  the  arachnoid  membrane,  which  extend  along  each 
nerve  from  the  visceral  to  the  parietal  layer. 

Striicliire. — When  examined  under  the  microscope,  the  arachnoid  is 
found  to  consist  of  bundles  of  fibres  like  those  of  fibrous  tissue,  inter- 
laced with  one  another.  A simple  layer  of  scaly  epithelium  can  be 
demonstrated  on  various  parts  of  its  free  surface,  and  probably  exists 
all  over. 

Cerebrospinal  fluid. — This  is  a very  limpid  serous  fluid, Jwhich  occupies  the  sub- 
arachnoid space.  When  collected  immediately  after  death,  its  quantity  was 
found  by  Magendie  in  the  human  subject  to  vary  from  two  drachms  to  twc 
ounces.  It  is  slightly  alkaline,  and  consists,  according  to  an  analysis  by  Las- 
saigne,  of  98-5  parts  of  water,  the  remaining  1'5  per  cent,  being  solid  matter, 
animal  and  saline.  In  e.xperiments  made  on  the  dog,  it  was  found  by  Magendie 
to  be  reproduced  in  thirty-si.x  hours,  after  it  had  been  drawn  off  by  puncturing 
the  membrane  at  the  lower  part  of  the  cord. 

Its  chief  use  is  probably  mechanical,  there  being  obvious  advantages  in  the 
delicate  structm'es  placed  w'ithin  the  cranium  and  spine  being  surrounded  by  a 
fluid  medium.  As  just  now  stated,  it  is  rapidly  secreted,  and  perhaps  it  is  also 
as  readily  absorbed;  and  thus,  being  easily  susceptible  of  changes  in  its  quantity, 
it  may,  in  this  w^ay,  admit  of  variations  in  the  amount  of  blood  circulating  in  the 
vessels  of  the  brain  and  spinal  cord,  although  the  cranio-vertebral  cavity  in  which 
they  are  lodged  does  not  vary  in  its  capacity. 

fjigamenlum  denliculatum. — This  is  a narrow  fibrous  band  which 
runs  along  each  side  of  the  spinal  cord  in  the  subarachnoid  space, 
between  ihe  anterior  and  posterior  roots  of  the  nerves,  commencing 
above  at  the  foramen  magnum  and  reaching  down  to  the  lower  pointed 
end  of  the  cord.  By  its  inner  edge  this  band  is  connected  with  the 
pia  mater  of  the  cord.  Its  outer  margin  is  widely  scolloped  or  ser- 
rated, and  the  points  of  its  serratures  or  denticulations  are  attached, 
ill  the  intervals  between  the  nerves,  to  the  inner  surface  of  the  dura 
mater,  being  covered  at  their  insertion  by  the  arachnoid  membrane. 
Tlie  first  or  highest  denticulation  is  fixed  opposite  the  margin  of  the 
foramen  magnum,  between  the  occipital  artery  and  the  hypoglossal 
nerve;  and  the  others  follow  in  order,  alternating  with  the  successive 
pairs  of  spinal  nerves.  In  all,  there  are  about  twenty-two  of  these 
points  of  insertion.  At  the  lower  end,  the  ligamentum  denticulatum  is 
continued  into  the  terminal  filament  of  the  spinal  cord,  which  thus 
connects  it  to  the  dura  mater  at  the  lower  end  of  the  sheath,  and 
might,  therefore,  although  much  longer,  be  compared  with  its  lateral 
denticulations. 

Structure. — It  consists  of  white  fibrous  tissue,  mixed  with  many 
exceedingly  fine  elastic  fibres,  seen  on  applying  acetic  acid.  It  is 
obviously  continuous  on  the  one  hand  with  the  fibrous  tissue  of  the 
pia  mater,  and  with  that  of  the  dura  mater  on  the  other. 

The  use  of  the  ligamentum  denticulatum  is  obviously  to  support  the 
cord  and  its  nerves. 

The  pia  mater  of  the  cord  presents  a conspicuous  fibrous  band, 

have  since  found,  however,  that  this  view  will  not  .stand  tlic  test  of  microscopic  scrutiny  : 
fJjr  the  internal  layer  has  not  the  defined  surface  of  a serous  membrane,  but  is  compo.sed 
of  openly-reticulated  bundles  offilaments,  like  cellular  tissue. — W.  S. 


DEVELOPMENT  OF  BRAIN  AND  SPINAL  CORD. 


253 
This  was 


runninsc  down  in  front  over  the  anterior  median  fissure. 

O 

named  by  Haller,  linea  splendens. 

BLOOD-VESSELS  OF  THE  BRAIN  AND  SPINAL  CORD. 


The  arteries  of  the  brain  and  in  part  those  of  the  spinal  cord  are 
derived  from  the  internal  carotid  and  vertebral  arteries.  These  vessels 
having  passed  across  the  arachnoid  cavity,  get  into  the  subarachnoid 
space  and  then  divide  and  subdivide  into  branches,  which,  in  their 
further  course  to  the  nervous  centres,  are  supported  by  the  pia  mater, 
and,  it  may  be  remarked,  are  more  deeply  placed  in  the  various  fis- 
sures and  sulci  than  the  small  veins,  which  do  not  accompany  the 
arteries,  but  pursue  a different  course  and  are  seen  upon  the  surface 
of  the  pia  mater. 

Moreover,  it  is  also  to  be  observed,  that  whilst  the  main  branches 
of  the  arteries  are  situated  at  the  base  of  the  brain,  the  principal  veins 
tend  towards  the  upper  surface  of  the  hemispheres,  where  they  enter 
the  superior  and  inferior  longitudinal  sinuses  : the  veins  of  Galen, 
however,  coming  from  the  lateral  ventricles  and  choroid  plexuses,  run 
backwards  to  the  straight  sinus. 


DEVELOPMENT  OF  THE  BRAIN  AND  SPINAL  CORD. 


Fig.  .‘t49. 


The  cerebro-spinal  axis,  with  the  cranio-vertebral  cavity  surrounding  it,  is  the 
part  of  the  embryo  which  first  begins  to 
be  formed.  It  commences  in  the  external 
or  serous  layer  of  that  portion  of  the 
ovum  which  has  been  named  the  blasto- 
derma  or  germinal  membrane,  in  form  of 
a groove  dilated  at  orle  extremity,  and 
bounded  by  two  ridges  named  the  dorsal 
plates  (laminae  dorsales).  See  fig.  349, 
and  description  of  that  figure. 

On  each  side  of  the  groove,  near  its 
middle,  the  small  quadrangular  rudiments 
of  the  vertebrae,  fig.  349,®  begin  to  appear 
in  the  substance  of  the  dorsal  plates  j 
while  a thin  portion  of  each  dorsal  plate 
next  the  groove  is  destined  to  form,  along 
with  its  fellow  of  the  opposite  side,  the 
rudiments  of  the  cerebro-spinal  axis. 

In  the  progress  of  development,  the 
dorsal  plates  unite  over  the  groove,  at 
first  in  the  middle  and  then  at  the  extre- 
mities, and  thus  convert  it  into  a canal, 
in  which  the  commencing  brain  and  spinal 
cord  may  soon  be  discovered.  The  en- 
larged or  cephalic  end,  of  this  cranio- 
vertebral canal,  as  it  might  be  named,  is  great  extent,  and  converted  it  into  a canal ; 
dilated  into  three  vesicles,  which  the  dilated  cephalic  extremity  is  seen  at  2; 

afterwards  form  the  cranial  cavity,  and  in  2 to  9 i.s  the  groove  partly  closed  ; 9 is 
which  the  encephalon  is  developed  ; 

1 > X r 1 /.I  ^ afterwards  as  ihe  rnomboidal  sinus.  8.  Kudi- 

wliilst  the  remaitiing  part  of  the  canal  (the  ments  of  the  vertebrje.  — b.  The  groove  13 
vertebral  part)  ultimately  contains  the  closed  except  at  9— the  rhomboidai  smus.  8. 
spinal  cord.  Plates  of  vertebrte.  10.  Anierioror  first  vesicle; 

The  matter  of  which  the  cerebro-spinal  ILs^^ond  or  middle;  and  12, third  or  posterior 
a.xis  is  at  first  composed  soon  separates, 

according  to  Baer,  into  an  external  layer,  which  forms  its  membranous  envelopes, 

VOL.  II.  22 


Shows  the  early  condition  of  the  nervous 
centres  in  the  embryo  of  the  fowl — (Reichert). 
A.  The  sides  of  the  groove  have  united  in  a 


254 


DEVELOPMENT  OF  ENCEPHALON. 


and  an  internal  tubular  portion,  which  afterwards  becomes  the  proper  nervous 
substance. 

DEVELOPMENT  OF  THE  SPINAL  CORD. 

The  spinal  cord,  formed,  as  already  stated,  by  the  union  of  two  lamellae  derived 
from  the  inner  surface  of  the  dorsal  plates,  is  at  first  a groove  open  in  its  whole 
length  on  the  dorsal  aspect ; but  the  edges  of  this  groove  soon  meet,  so  as  to 
form  a medullary  tube.  At  the  ninth  week,  Tiedemann*  has  seen  the  borders  of 
this  groove  still  apart ; at  the  twelfth  they  were  in  close  contact,  so  as  to  form  a 
sort  of  tube,  but  they  could  be  easily  separated  from  one  another.  The  perfect 
closing  of  this  groove  is  delayed  towards  the  lower  end  of  the  cord,  which  is 
slightly  enlarged,  and  presents  a longitudinal  median  slit,  analogous  to  the  rhom- 
boidal  sinus  in  birds. — Fig.  349,  “ ®. 

The  central  cavity  of  the  medullary  tube  formed  by  the  closure  of  the  groove, 
is  gradually  narrowed  by  the  thickening  of  the  two  halves  of  the  cord  and  by  the 
deposition  of  gray  matter,  and  at  last  is  obliterated  in  the  human  species  through- 
out its  entire  length,  except  for  about  half  an  inch  below  the  fourth  ventricle.  In 
many  animals,  however,  it  is  persistent  throughout  life.. 

The  anterior  fissure  of  the  cord  is  developed  very  early,  and  contains  even  at 
first  a process  of  the  pia  mater. 

The  "cervical  and  lumbar  enlargements,  opposite  the  attachments  of  the  brachial 
and  crural  nerves,  appear  at  the  end  of  the  third  month  : in  these  situations  tlie 
central  canal,  at  that  time  not  filled  up,  is  somewhat  larger  than  elsewhere. 

At  first  the  cord  occupies  the  whole  length  of  the  vertebral  canal,  so  that  there 
is  no  cauda  equina.  At  the  beginning  of  the  fourth  month,  the  vertebrae  having 
grown  faster  than  the  cord,  the  latter  seems  as  it  were  to  have  retired  up  into  the 
canal,  and  the  cauda  equina  is  commenced.  At  the  ninth  month,  the  lower  end 
of  the  cord  is  opposite  the  third  lumbar  vertebra. 

DEVELOPMENT  OF  THE  ENCEPHALON. 

The  three  cephalic  dilatations  of  the  primitive  cranio-vertebral  cavity,  fig.  349, 
B,  ",  ",  contain  three  hollow  vesicles  oi  nervous  matter,  which  are  the  rudiments 
of  the  future  encephalon. 

The  anterior  or  first  vesicle  soon  becomes  divided  into  an  anterior  and  a poste- 
rior portion.  The  anterior  portion  forms  the  principal  mass  of  the  hemispheres, 
fig.  350,  A “,  with  the  corpora  striata,  ’’ ; whilst  the  posterior  portion,  is  deve- 
loped into  the  thalami  and  third  ventricle. 

The  second  or  middle  vesicle,  ■*,  forms  the  corpora  quadrigemina  above,  and  the 
crura  cerebri  below, — its  cavity  remaining  as  the  Sylvian  aqueduct. 

The  third  or  posterior  vesicle,  ® to  continues  incomplete  above  for  some  time, 
as  far  as  nervous  substance  is  concerned.  At  length  its  anterior  portion,  is 
closed  over  and  forms  the  cerebellum  above,  whilst  on  its  under  surface  the  pons 
Varolii  appears.  The  posterior  portion,  on  the  other  hand,  continues  open  on 
its  dorsal  aspect,  and  forms  the  medulla  oblongata  and  fourth  ventricle. 

These  three  vesicles,  at  first  arranged  in  a straight  line,  one  before  the  other, 
soon  alter  their  position,  in  correspondence  with  the  curving  downwards  of  the 
cephalic  end  of  the  embryo.  Thus  at  the  seventh  week,  as  figured  by  Tiede- 
mann, there  is  an  angular  bend  forwards  between  the  hindmost  vesicle  and  the 
rudimentary  spinal  cord,  ’, — the  projecting  angle  (backwards)  being  named  the 
cervical  tuberosity,  Another  bend,  but  in  the  opposite  clirection,  exists  be- 
tween that  part  of  the  third  vesicle  which  forms  the  medulla  oblongata,  and  that 
which  gives  rise  to  the  cerebellum,  Lastly,  a third  angle  is  produced  by  a 
bend  forwards  and  downwards  in  the  region  of  the  middle  vesicle,  ■*,  from  which 
the  corpora  quadrigemina  are  developed,  and  which  forms,  at  this  period,  the 
highest  part  of  the  encephalon ; whilst  the  anterior  or  first  vesicle,  is  bent 

nearly  at  a right  angle  downwards. 

* To  save  the  repetition  of  references,  it  may  be  stated  here,  that  the  description  of  the 
successive  changes  of  development  in  the  spinal  cord  and  brain,  and  the  periods  at  which 
they  occur,  are  taken  from  Tiedemann’s  account.  Anatomie  und  Bildungsgeschichte  des 
Gehirns.  Niirn  berg,  1816. 


DEVELOPMEiNT  OF  PRIMARY  VESICLES. 


255 


At  a later  period  of  development,  this  first  vesicle,  which,  as  stated  above,  re- 
presents the  cerebral  hemispheres,  increases  greatly  in  size  upwards  and  back- 
wards, and  gradually  covers  first  the  thalami,  then  the  corpora  quadrigemina,  and 
lastly  the  cerebellum. 


On  laying  open  the  rudimentary  en- 
cephalon, two  tracts  of  nervous  matter 
are  seen  to  be  prolonged  upwards  from 
the  spinal  cord  upon  the  floor  of  the 
cephalic  vesicles : these  tracts,  which 
are  doubtless  connected  with  the  ante- 
rior and  lateral  parts  of  the  cord,  are 
the  rudiments  of  the  crura  cerebri  and 
corresponding  columns  of  the  medulla 
oblongata. 


Fig.  350. 


Fig.  350. — These  figures  show  the  early  form 
of  the  brain  and  spinal  cord  in  the  human  em- 
bryo (Tiedemann). — A.  At  the  seventh  week, 
viewed  from  the  side.  1.  SpTnal  cord.  2 to  3 
isthe  third  vesicle  ; 4,  the  middle  vesicle  ; 5,6,7, 
the  first  or  anterior  vesicle.  2,  is  on  the  hind 
part  of  medulla,  or  the  cervical  tuberosity.  3. 

The  cerebellum.  4.  Corpora  quadrigemina. 

5.  Optic  thalami.  6.  Cerebral  hemisphere.  7. 

Corpus  striatum. — B.  At  the  ninth  week,  seen 
from  behind.  1.  Spinal  cord  and  medulla  ob- 
longata. open  behind.  2.  Cerebellum.  3.  Cor- 
pora quadrigemina.  4.  Thalami,  still  uncovered. 

5.  Right  and  left  hemispheres,  now  very  thin. 

— C,  D.  At  the  twelfth  week,  side  and  back 
views,  a.  Cerebrum,  b.  Corpora  quadrige- 
rcina.  c.  Cerebellum,  d.  Medulla  oblongata. 

N.B.  The  thalami  at  this  period  are  covered  by 
the  cerebral  hemi.spheres. — E,  F.  At  the  twelfth 
week:  in  £,  which  is  seen  from  behind,  the 
hemispheres  are  reflected  outw'ards.  1.  Cord 
and  medulla  oblongata.  2.  Cerebellum.  3. 

Corpora  qu.idrigemina.  4.  Thalami,  which  are 
here  uncovered  by  the  reflection  of  the  hemi- 
spheres. 5,  6.  The  right  corpus  striatum, 
embedded  in  the  hemispheres.  7.  The  point  of 

commencement  of  corpus  callosum.  F.  Is  a vertical  median  section,  showing  the  cavity  from  the 
cord  up  to  the  third  ventricle.  1,2.  Spinal  cord  and  medulla,  still  hollow.  3.  Bend  at  which 
pons  Varolii  is  to  be  formed.  4.  Cerebellum.  5.  Lamina  (superior  peduncles)  leading  up  to 
corpora  quadrigemina.  6.  Crura  cerebri.  7.  Corpora  quadrigemina.  8.  Third  ventricle.  9. 
Infundibulum.  10.  Thalamus,  now  solid.  11.  Optic  nerves.  12.  Cleft  leading  into  lateral  ven- 
tricle. 13.  Commencing  corpus  callosum. 


FURTHER  DEVELOPMENT  OF  THE  PRIMARY  VESICLES. 

The  third  vesicle. — The  posterior  portion  of  this  vesicle,  corresponding  with  the 
medulla  oblongata,  is  never  closed  above  by  nervous  matter.  The  open  part  of 
the  medullary  tube  constitutes  the  floor  of  the  fourth  ventricle,  which  communi- 
cates below  with  the  canal  of  the  spinal  cord,  and  eventually  forms  the  calamus 
scriptorius. 

The  three  elements  of  the  medulla  oblongata  begin  to  be  distinguished  about 
the  third  month ; first,  the  restiform  bodies,  which  are  connected  with  the  com- 
mencing cerebellum,  and  afterwards  the  anterior  pyramids  and  olives.  The  ante- 
rior pyramids  become  prominent  on  the  surface  and  distinctly  defined  in  the  fifth 
month;  and  by  this  time  also  their  decussation  is  evident.  The  olivary  fasciculi 
are  early  distinguishable,  but  the  proper  olivary  body,  or  tubercle,  does  not  appear 
tiU  about  the  si.vth  month.  The  fasciola  cinerea  of  the  fourth  ventricle  can  be  seen 
at  the  fourth  or  fifth  month,  but  the  white  strice  not  until  after  birth. 

The  anterior  part  of  the  third  vesicle  is  soon  closed  above  by  nervous  sub- 
stance, and  forms  the  commencing  cerebellum,  a,  This  part  exists,  b,  about 


256 


DEVELOPMENT  OF  PRIMARY  VESICLES. 


the  end  of  the  second  month,  as  a delicate  medullary  lamina,  forming  an  arch 
behind  the  corpora  quadrigemina  across  the  widely-open  primitive  medullary 
tube. 

According  to  Bischoff,  the  cerebellum  does  not  commence  by  two  lateral  plates 
which  grow  up  and  meet  each  other  in  the  middle  line;  but  a continuous  deposit 
of  nervous  substance  takes  place  across  this  part  of  the  medullary  tube,  ajid 
closes  it  in  at  once'.  This  layer  of  nervous  matter,  which  is  soon  connected  with 
the  corpora  restilormia,  or  inferior  peduncles,  increases  gradually  up  to  the  fourth 
month  (see  c,  d,  c,  also  e,  “),  at  which  time  there  may  be  seen  on  its  under  sur- 
face the  commencing  corjjus  dentatum : in  the  fifth  month,  a division  into  five  lobes 
has  taken  place ; at  the  sixth,  these  lobes  send  o\xX  folia,  which  are  at  first  simple, 
but  afterwnrds  become  subdivided.  Moreover,  the  hemispheres  of  the  cerebellum 
are  now  relatively  larger  than  its  median  portion,  ox  worm.  In  the  seventh  month 
the  organ  is  more  complete,  and  the  flocculus  and  posterior  velum,  w’ith  the  other 
parts  of  the  inferior  vermiform  process,  are  now  distinguishable,  except  the  amyg- 
dala, which  are  later  in  their  appearance. 

Of  the  peduncles  of  the  cerebellum,  the  inferior  pair  (corp.  re'stiformia)  are  the 
first  seen — viz.,  about  the  third  month;  the  middle  pedjjncles  are  perceptible  in 
the  fourth  mouth ; and  at  the  fifth,  the  superior  peduncles  and  the  Vieussenian 
valve,  F The  pons  Varolii  is  formed,  as  it  were,  by  the  fibres  from  the  hemi- 
spheres of  the  cerebellum,  embracing  the  pyramidal  and  olivary  fasciculi  of  the 
medulla  oblongata.  According  to  Baer,  the  bend  which  takes  place  at  this  part 
of  the  encephalon — just  over  % a,  also  at  ® r — thrusts  down  a masfe  of  nervous 
substance  before  any  fibres  can  be  seen  ; and  in  this  substance  transverse  fibres, 
continuous  with  those  of  the  cerebellum,  are  afterwards  developed.'  From  its  re- 
lation to  the  cerebellar  hemispheres,  the  pons  keeps  pace  with  them  in  its 
growuh ; and,  in  conformity  with  this,  its  transverse  fibres  are  few,  or  entirely 
wanting  in  those  animals  in  which  there  is  a corresponding  deficieircy  or  absence 
of  the  lateral  parts  of  the  cerebellum. 

The  second  or  middle  vesicle. — The  corpora  qiiadrigemina — a,'*,  b and  e,“;  c and  d, 
b — are  formed  in  the  upper  part  of  the  middle  cephalic  vesicle,  a,  the  hollow 
in  the  interior  of  which,  shown  in  d,  communicates  with  those  of  the  first  and 
third  vesicles.  The  corpora  quadrigemina,  in  the  early  condition  of  the  human 
embryo,  are  of  great  proportionate  volume,  in  harmony  with  what  is  seen  in  the 
lower  vertebrata,  but  subsequently  they  do  not  grow  so  fast  as  the  anterior  parts 
of  the  encephalon,  and  are  therefore  sootr  reached  by  the  cerebral  hemispheres, 
which  at  the  sixth  month  cover  them  in  completely.  Moreover,  they  become 
gradually  solid,  by  the  deposition  of  matter  within  them;  and  as,  in  the  mean 
time,  the  cerebral  peduncles,  d,“,  are  growing  rapidly  in  size  in  the  floor  of  this 
second  cephalic  vesicle,  the  cavity  in  its  interior  is  quickly  filled  up,  with  the 
exception  of  the  narrow  passage  named  the  Sylvian  aqueduct.  The  fillet  is  distin- 
guishable in  the  fourth  month.  The  corpora  quadrigemina  of  the  two  sides  are 
not  marked  off  from  each  other  by  a vertical  median  groove  until  about  the  sixth 
month;  and  the  transverse  depression  sej^arating  the  anterior  and  posterior  pairs  is 
first  seen  about  the  seventh  month  of  intra-uterine  life. 

The  first  or  anterior  vesicle,  a,’,",’’. — This  vesicle,  as  already  stated,  is  divided 
into  two  portions — viz.,  a posterior,  which  is  developed  into  the  optic  thalami  and 
third  ventricle,  and  an  anterior,  which  forms  the  principal  mass  of  the  cerebral 
hemispheres,  including  the  corpora  striata. 

a.  The  two  optic  thalami — a,'^  b and  c,* — consist,  therefore,  at  first  of  a single 
hollow  sac  of  nervous  matter,  the  cavity  of  which  communicates  in  front  with  the 
interior  of  the  commencing  cerebral  hemispheres,  and  behind  with  that  of  the 
middle  cephalic  vesicle  (corpora  quadrigemina).  Soon,  however,  by  means  of  a 
deposit  taking  place  in  their  interior,  behind,  below,  and  at  the  sides,  the  thalami 
become  solid,  r,'-*,  and  at  the  same  time  a cleft  or  fissure  appears  between  tlicin 
above,  and  penetrates  down  to  the  internal  cavity,  which  continues  open  at  the 
back  part  opposite  the  entrance  of  the  Sylvian  aqueduct.  This  cleft,  or  fissure,  is 
the  third  ventricle.  Behind,  the  two  thalami  continue  united  by  the  posterior  com- 
missure, which  is  distinguishable  about  the  end  of  the  third  month,  and  also  by 
the  peduncles  of  the  pineal  gland.  The  soft  commissure  could  not  be  detected  by 


DliVELOPMEINlT  OF  PRIMARY  VESICLES.  257 

Tiedemann  until  the  ninth  month;  but  its  apparent  absence  at  earlier  dates  may 
perhaps  be  attributed  to  the  effects  of  laceration. 

At  an  early  period  the  optic  tracts  may  be  recognised  as  hollow  prolongations 
from  the  outer  part  of  the  wall  of  the  then  vesicular  thalami.  At  the  fourth  month 
these  tracts  are  distinctly  formed. 

The  pineal  gland,  according  to  Baer,  is  developed  from  the  back  part  of  the 
thalami,  where  those  bodies  continue  joined  together ; but  it  is  suggested  by  Bis- 
choff  that  its  development  may  be  rather  connected  with  the  pia  mater.  It  was 
not  seen  by  Tiedemann  until  the  fourth  month : subsequently,  its  growth  is  very 
slow ; and  it  at  first  contains  no  gritty  deposit,  which,  however,  was  found  by 
Scemmerring  at  birth. 

The  tuber  cinereum  may  be  recognised  on  the  under  surface  of  the  first  vesicle 
before  the  third  month,  according  to  Valentin,  who  thinks  that  its  development  is 
connected  with  that  of  the  corpora  albicantia. 

The  infundibulum,  e,“,  appears  at  a very  early  period,  extending  from  the  lower 
part  of  the  anterior  cephalic  vesicle  into  a depression  in  the  base  of  the  rudi- 
mentary cranium.  It  is  thought  by  Baer  to  be  the  anterior  extremity  of  the 
primitive  medullary  tube. 

Bathke  asserts,  on  the  ground  of  observations  recently  made,  that  the  first  con- 
dition of  the  pituitary  body  is  that  of  a small  sac  or  pouch  derived  from  the  mucous 
membrane  of  the  pharynx,  which  is  prolonged  upwards  into  the  base  of  the 
cranium,  in  the  form  of  a cul  de  sac,  and  reaches  the  point  of  the  infundibulum. 
This  sac  is  afterwards  shut  off  from  the  pharyngeal  cavity,  and  the  closed  vesicle 
thus  formed  becomes  attached  to  the  infundibulum,  and  constitutes  the  pituitary 
body.  Reichert,  on  the  other  hand,  regards  this  body  as  the  remains  of  the  ante- 
rior extremity  of  the  corda  dorsalis.  Tiedemann  describes  it  as  a large  soft  mass 
at  the  end  of  the  third  month. 

b.  The  corpora  striata,  which,  With  the  rest  of  the  cerebral  hemispheres,  are 
evolved  from  the  anterior  portion  of  the  first  cephalic  vesicle,  at  ?,  a,  appear  as 
two  dark  masses  rising  up  from  the  floor  of  that  part  of  the  vesicle,  one  on  each 
side.  Unlike  the  thalami,  the  corpora  striata,  e,“  are  always  concealed,  being 
included  from  the  first  in  the  vesicular  cerebral  hemispheres,  into  the  cavity  of 
which  they  soon  project  from  the  outer  side  and  from  below. 

The  right  and  left  cerebral  hemispheres,  which  at  first  are  proportionately  small, 
appear  as  two  little  hollow  vesicles,  a,“,  which  bud  out,  one  on  each  side,  from 
the  fore  part  of  the  anterior  primary  cephalic  vesicle  ; and  as  these  go  on  growing 
laterally,  a longitudinal  median  depression  is  soon  formed  between  them,  b,^. 
Continuing  to  remain  hollow,  but  yet  enlarging,  and  having  their  walls  increased 
in  thickness,  the  hemispheres  form,  during  the  fourth  month  (Tiedemann),  two 
smooth  shell-like  lamellae,  c and  n,  a,  which  include  the  cavities  afterwards  named 
the  lateral  ventricles,  and  the  parts  contained  within  them.  Following  out  the  sub- 
sequent changes  affecting  the  exterior  of  the  cerebral  hemispheres,  it  is  found  that 
about  the  fourth  month  the  first  traces  of  some  of  the  convolutions  appear,  the 
intermediate  sulci  commencing  only  as  very  slight  depressions . on  the  hitherto 
smooth  surface.  Though  the  hemispheres  continue  to  grow  quickly  upwards  and 
backwards,  the  convolutions  become  distinct  by  comparatively  slow  degrees  at 
first ; but  towards  the  seventh  and  eighth  months  they  are  developed  with  great 
rapidity,  and  at  the  beginning  of  the  last  month  of  intra-uterine  life  appear  to  be 
completely  formed. 

The  Sylvian  fissure,  which  afterwards  separates  the  anterior  from  the  middle 
lobe  of  each  hemisphere,  begins  as  a very  slight  depression  between  them  about 
the  fourth  month. 

From  the  earliest  period  the  hemispheres,  e,^,  conceal  the  corpora  striata, s;  by 
the  end  of  the  third  month  they  have  extended  so  far  backwards  as  to  have 
covered  the  thalami,  e,‘‘,  f,">  ; at  the  fourth,  they  reach  the  corpora  quadrigemina  : 
at  the  sixth,  they  cover  those  bodies  and  great  part  of  the  cerebellum,  beyond 
which  they  project  backwards  by  the  end  of  the  seventh  month. 

Between  and  within  the  hemispheres  other  changes  take  place.  At  first  there 
is  no  corpus  callosum,  and  no  fornix ; nor  is  there  any  separation  of  the  common 
internal  cavity  into  two  lateral  cavities  or  ventricles. 

According  to  Tiedemann,  the  corpms  callosum,  which  certainly  commences  in 

2-Z* 


4 


258 


MEMBRANES  OF  THE  ENCEPHALON. 


front,  is  first  seen  about  the  end  of  the  third  month,  as  a narrow  vertical  band  or 
coininissure — e,'  f,'=’ — extending  across  between  the  fore  part  of  the  two  hemi- 
sjiheres.  Subsequently  it  becomes  horizontal,  and  grows  backward^  together 
with  the  hemispheres,  until  it  completely  covers  the  optic  thalami.  Tiedemann 
considers  that  it  results  from  the  junction  across  the  median  plane  of  the  radiating 
fibres  of  the  hemispheres.  In  the  same  way,  he  supposes  that  the  anterior  com- 
missure, which  is  seen  during  the  third  month,  is  formed  by  the  union  of  other 
peduncular  fibres,  which  have  passed  through  the  corpora  striata. 

Bischoff,  however,  is  of  opinion  that  the  corpus  callosum  has  its  origin  in  the 
part  of  the  anterior  primitive  vesicle,  situated  between  the  rudimentary  hemi- 
spheres, where  these  continue  united  together  in  front,  at  the  bottom  of  the  median 
longitudinal  depression  which  is  formed  between  them.  From  this  point,  he 
describes  it  as  extending  backwards  over  the  thalami. 

The  fornix,  like  the  corpus  callosum,  appears  to  be  formed  in  conjunction  with 
the  hemispheres.  According  to  Bischoff,  its  anterior  pillars  begin  near  the  same 
point  as  the  commencing  corpus  callosum,  but  of  course  behind  it : whilst  the 
body  and  posterior  pillars  are  formed  upon  the  internal  and  posterior  borders  of 
the  growing  hemispheres.  The  fornix  certainly  commences  in  front,  like  the 
corpus  callosum.  Burdach  says  its  anterior  pillars  are  seen  about  the  same  time 
as  the  rudiments  of  this  latter  body  (second  month) ; but  Tiedemann  and  Valentin 
place  the  period  at  the  end  of  the  third  month, — the  corpora  albicantia  having 
appeared  a little  earlier,  at  first  as  a single  mass.  The  posterior  pillars  are  not 
seen  until  the  fourth  or  fifth  month.  Their  free  border  forms  the  corpus  fimbriatvm 
on  each  side,  and  their  enlarged  extremity  appears  then  to  constitute  the  com- 
mencing pes  hippocampi,  the  indentations  upon  which,  however,  are  not  evident 
until  the  ninth  month.  The  hippocampus  minor  appears  at  the  end  of  the  fourth 
month,  as  a folding  inwards  of  the  hemisphere  into  the  ventricular  cavity. 

In  the  course  of  development,  the  fore  part  of  the  fornix  separates  from  the 
under  surface  of  the  corpus  callosum,  leaving  two  thin  vertical  lamellse,  which 
form  the  septum  lucidum,  and  the  intermediate  fifth  ventricle.  At  first,  this  ventricle 
communicates  with  the  cavity  of  the  third  ventricle  below,  but  it  is  afterwards 
completely  occluded  by  the  union  of  the  two  lamellsE.  The  septum  and  filth 
ventricle  are  recognised  only  about  the  fifth  month. 

In  the  first  instance,  the  vesicular  cerebral  hemispheres  enclose  a common 
cavity ; but  as  the  median  longitudinal  depression  is  formed  between  them,  as 
the  corpus  callosum  and  fornix  are  developed  from  before  backwards,  and  as  the 
septum  lucidum  descends  from  one  to  the  other  in  the  median  plane,  this  single 
cavity  is  divided  into  the  two  lateral  ventricles,  which  after  a time  communicate 
with  each  other,  and  with  the  third  ventricle,  by  a narrow  slit,  r,'^;  and,  finally, 
only  by  the  foramen  of  Monro.  The  form  of  each  ventricular  cavity  depends 
upon  that  of  the  several  parts  which  project  into  it.  Thus  its  anterior  cornu  is 
produced  around  the  anterior  extremity  of  the  corpus  striatum,  and  its  descending 
cornu  behind  the  thalamus  and  below  the  striated  body.  The  posterior  cornu  is 
later  in  its  appearance,  and  is  developed  in  the  sub.stance  of  the  posterior  lobe, 
as  that  extends  itself  backwards.  The  lateral  ventricles,  or  rather  the  parts  of 
which  their  walls  are  composed,  do  not  acquire  their  characteristic  forms  until  the 
eighth  or  ninth  month. 

GRAY  AND  WHITE  SUBSTANCE  OF  THE  NERVOUS  CENTRES. 

The  distinction  between  the  gray  and  white  substances  is  not  at  first, to  be  made 
out;  but  there  is  no  evidence  to  show  that  one  precedes  the  other  in  its  formation. 
Valentin  states  that  he  has  distinguished  the  one  from  the  other  at  the  third  month : 
less  from  the  difference  in  their  colour  than  from  their  microscopic  characters.  [ 

MEMBRANES  OF  THE  ENCEPHALON.  j| 

It  is  remarked  by  Bischoff,  that  the  membranes  of  the  brain  are  everywhere  > 
formed  by  the  separation  of  the  outer  layer  of  the  primitive  cephalic  mass;  and 
thus,  that  the  pia  mater  does  not  send  inwards  processes  into  the  fissures  or  sulci, 
or  into  the  ventricular  cavities ; but  that  every  part  of  this  vascular  membrane. 


CRANIAL  NERVES. 


259 


including  the  choroid  plexuses  and  velvra  interpositum,  is  formed  in  its  proper  position 
upon  the  nervous  matter. 

The  pia  mater  and  dura  mater  have  both  been  detected  about  the  seventh  or 
eighth  week,  at  which  period  the  tentorium  cerebelli  existed.  At  the  third 
month,  the  falx  cerebri,  with  the  longitudinal  and  lateral  sinuses,  could  be  made 
out;  and  the  choroid  plexuses  of  both  the  lateral  and  fourth  ventricles  were 
distinguishable.  No  trace  of  arachnoid,  however,  could  be  seen  until  the  fifth 
month. 


CKANIAL  NERVES. 


All  nerves  issuing  from  the  cerebro-spinal  centre  which  are  trans- 
mitted through  apertures  in  the  base  of  the  skull,  are  included  in  the 
class  of  cranial  nerves. 

These  nerves  are  named  numerically,  according  to  the  relative 
position  of  the  apertures  for  their  transmission  through  the  cranium  ; 
and  they  are  likewise  distinguished  by  other  names,  taken  chiefly  from 
the  organs  or  parts  to  which  they  are  distributed  (e.  g.  facial,  glosso- 
pharyngeal), or  from  the  functions  to  which  they  minister  (olfactory, 
optic,  &c.) 

The  number  of  the  cranial  nerves  is  differently  stated  by  anatomists. 
The  difference  is  mainly  owing  to  the  circumstance,  that  under  one 
system  the  nerves  which  enter  the  internal  auditory  meatus,  and  those 
which  pass  through  the  jugular  foramen,  are  in  each  case  considered 
a single  pair  (seventh  and  eighth)  divisible  into  parts;  while  under 
another  system  each  of  the  nerves  is  numbered  separately.  The 
classifications  exemplifying  the  two  modes  of  numbering  — those  of 
Willis  and  Soemmerring — are  subjoined: — 


First  pair  of  nerves,  Olfactory  nerves. 
“ Optic. 

“ Oculo-motor. 

“ Pathetic. 

(c  1 Trifacial  or 
( trigeminal. 

“ Abducent-ocular, 

nervus  durus.  Facial, 
n.  mollis, 


Second 

Third 

Fourth 

Fifth 

Sixth 

Seventh 


Eighth 

Ninth 

Tenth 


n.  vagus,* 

I n.  accesso- 
rius, 


Auditory. 
Pneumogas- 
tric. 

Spinal  ac- 
\ cessory. 
Lingual  or  hypo- 
glossal. 
Suboccinital. 


SCEMMERRING. 


The  first  six  names  are  the  same  as 
those  of  Willis. 


Seventh  pair  of  nerves.  Facial  nerves. 

“ Auditory. 

a ( Glosso-pharyn- 


Eighth 

Ninth 

Tenth 

Eleventh 

Twelfth 


geal. 
Pneumogastric. 
( Spinal  acces- 
[ sory. 
i Lingual  or 
( hypoglossal. 


The  arrangement  of  Scemmerring  is  the  preferable  one,  as  being 
the  simplest  and  most  natural ; for  each  of  the  parts  included  in  the 
seventh  and  eighth  pairs  of  Willis  is  really  a distinct  nerve.  But  as 
the  plan  of  Willis  is  in  general  use,  it  will  most  conveniently  be  fol- 

* Willis  described  the  glosso-pharyngeal  nerve  as  a branch  of  the  vagus. 


260 


OPTIC  NERVE. 


lowed  here : with  the  exception,  however,  that  the  tenth  pair  (sub- 
occipital)  of  that  anatomist  will  be  ranged  with  the  spinal  nerves. 
The  cranial  nerves  will  therefore  be  regarded  as  consisting  of  nine 
pairs. 

It  may  be  mentioned  that  some  anatomists,  looking  to  the  resemblance  between 
the  bones  of  the  skull  and  the  vertebrae  of  the  spinal  column,  have  endeavoured 
to  show  an  analogy  between  the  nerves  also.  Accordingly,  cranial  nerves  which 
possess  ganglia,  and  others  devoid  of  ganglia,  have  been  grouped  together,  so  as 
to  form  compound  nerves,  named  cranio-vertebral ; and  thus  regarded,  they  have 
been  looked  upon  as  analogous  to  spinal  or  (according  to  the  language  of  this 
system)  spini-vertebral  nerves.  The  arrangement  suggested  by  Professor  Muller 
wiU  illustrate  this  mode  of  viewing  the  cranial  nerves  : — 

1.  The  first  cranio-vertebral  nerve  is  composed  of  the  fifth,  third,  fourth,  si.xth 
(and  facial?)  nerves. 

2.  In  the  second  cranio-vertebral  nerve  are  included  the  pneumogastric,  glosso- 
pharyngeal, and  spinal  accessory  nerve. 

3.  The  hypoglossal  is  the  third  cranio-vertebral  nerve. 

OLFACTORY  NERVE. 

The  olfactory  or  first  cranial  nerve  (nervus  olfactorius,  par  pri- 
mum),  the  special  nerve  of  the  sense  of  smelling,  is  distributed  ex- 
clusively to  the  nasal  fossas.  The  course  of  this  nerve  within  the 
cranium  has  been  already  described  {ante,  page  243).  It  remains  to 
add  an  account  of  the  branches  as  they  are  distributed  in  the  interior 
of  the  nose. 

From  the  under  surface  of  the  olfactory  bulb,  fig.  355,  h numerous 
branches  proceed  through  the  holes  in  the  cribriform  plate  of  the  eth- 
moid bone,  each  being  invested  by  tubular  prolongations  of  the  mem- 
branes of  the  brain.  These  tubes  of  membrane  vary  in  the  extent  to 
which  they  are  continued  on  the  branches.  Thus  the  offsets  of  the 
dura  mater  sheathe  the  filaments,  and  join  the  periosteum  lining  the 
nose;  those  of  the  pia  mater  become  blended  with  the  neurilemma  of 
the  nerves ; and  those  of  the  arachnoid  reascend  to  the  serous  lining 
of  the  skull. 

The  branches  are  arranged  in  three  sets.  The  inner  set,  lodged  for 
a while  in  grooves  on  the  surface  of  the  bone,  ramify  in  the  pituitary 
membrane  of  the  septum  ; the  outer  set,  fig.  355,  extend  to  the  upper 
two  spongy  bones,  and  the  plane  surface  of  bone  in  front  of  these  ; and 
the  middle  set,  which  are  very  short,  are  confined  to  the  roof  of  the 
nose.  The  distribution  of  the  olfactory  nerves  is  confined  to  the  nasal 
fossae ; none  of  the  branches  reach  the  lower  spongy  bones. — (See 
Anatomy  of  the  Nose.) 

OPTIC  NERVE. 

The  optic  or  second  cranial  nerve  (nervus  opticus,  par  secundum), 
a nerve  of  special  sense,  belongs  exclusively  to  the  eye.  The  con- 
nexion of  this  nerve  with  the  nervous  centre,  and  the  optic  tract  with 
the  commissure  of  the  nerves  of  opposite  sides,  have  been  described  at 
a former  part  of  this  work  (page  244). 

From  the  commissure  at  the  base  of  the  brain,  each  nerve  diverges 
from  its  fellow,  becomes  round  and  firm,  and  is  incased  in  a neu- 
rilemma. In  the  orbit,  which  it  enters  by  the  optic  foramen, ‘it  is  in- 


THIRD  PAIR  OF  NERVES. 


261 


vested  with  a sheath  of  the  dura  mater,  and  surrounded  by  the  recti 
muscles;  and  finally,  after  piercing  successively  the  sclerotic  and 
choroid  coats  at  the  back  of  the  eyeball,  it  expands  into  the  retina. — 
(See.  the  Anatomy  of  the  Eye.) 


THIRD  PAIR  OF  NERVES. 


This  nerve,  the  common  motor  nerve  of  the  eyeball,  (nerv.  motorius 
oculi,  par  tertium,)  fig.  351,  % gives  branches  to  five  of  the  seven  mus- 
cles of  the  orbit. 

Like  the  other  motor  nerves,  the  third  is  round,  firm,  and  white;  it 
is  invested  from  the  first  by  a sheath  of  pia  mater,  and  afterwards  by 
a tube  of  the  arachnoid  membrane. 

In  its  course  to  the  orbit,  this  nerve  is  contained  in  the  external 
fibrous  boundary  of  the  cavernous  sinus  with  other  nerves ; and  on 
entering  the  canal  appropriated  to  it  in  the  dura  mater,  the  serous 
covering  of  the  arachnoid  is  reflected  from  it.* 


After  receiving  one  or  two  deli- 
cate filaments  from  the  cavernous 
plexus  of  the  sympathetic,  the 
third  nerve  divides  near  the  orbit 
into  two  parts,  which  are  con- 
tinued into  that  cavity  between 
the  heads  of  the  external  rectus 
muscle. 

Branches. — The  upper,  the  smaller 
division,  fig.  351,  is  directed  inwards 
over  the  optic  nerve  to  the  rectus  su- 
perior muscle  of  the  eye,  and  the  ele- 
vator of  the  eyelid,  to  both  which  mus- 
cles it  furnishes  offsets. 

The  lower  and  larger  division  of  the 
nerve,  fig.  354,  separates  into  three 
branches ; of  which  one  reaches  the 
inner  rectus;  another  the  lower  rectus; 
and  the  third,  the  longest  of  the  three, 
runs  onward  between  the  lower  and 
the  outer  rectus,  and  terminates  below 
the  ball  of  the  eye  in  the  inferior  ob- 
lique muscle.  The  last-mentioned 
branch  is  connected  with  the  lower 
part  of  the  lenticular  ganglion  by  a 
short  thick  cord,  and  gives  two  fila- 
ments to  the  lower  rectus  muscle. 


Fig.  351. 


The  deep  nerves  of  the  orbit  seen  from  above 
by  removing  the  bone  and  dividing  the  elevator 
of  the  upper  eyelid  and  the  upper  rectus  muscle. 
(From  Arnold.)  a.  Internal  pterygoid  muscle. 
b.  Temporal  muscle,  c.  Cut  surface  of  bone. 
d.  Elevator  of  the  eyelid  and  upper  rectus  mus- 
cle. e.  Carotid  artery.  1.  Optic  nerve.  2.  Fifth 
nerve.  3.  Ophthalmic  nerve.  4.  Third  nerve. 
5.  Sixth  nerve. 


The  several  branches  of  the  third  nerve  enter  the  muscles  to  which 
they  are  distributed,  on  that  surface  of  the  muscle,  in  each  case,  which 
looks  towards  the  eyeball. 

Position  of  certain  nerves  at  the  cavernous  sinus,  and  as  they  enter 
the  orbit. — As  several  nerves  are  placed  close  together  at  the  cavernous 
sinus,  and  as  they  enter  the  orbit  through  the  same  foramen,  a-  state- 
ment will  now,  once  for  all,  be  made  respecting  the  position  they  bear 


* For  an  account  of  the  relative  position  of  the  orbital  nerves  before  they  enter  the 
orbit,  see  the  statement  placed  after  description  of  this  (the  third)  nerve. 


262 


FOURTH  PAIR  OF  NERVES. 


one  to  the  other,  in  order  to  save  the  repetition  which  otherwise  would 
be  necessary  when  each  of  the  nerves  in  question  is  under  considera- 
tion. 

Al  the,  cavernous  sinus. — In  the  dura  materwhieh  bounds  the  cavernous 
sinus  on  the  outer  side,  tlie  third  and  fourth  nerves  and  the  ophthalmic 
division  of  the  fifth  are  placed,  as  regards  one  another,  in  their  nume- 
rical order,  both  from  above  downwards  and  from  without  inwards. 
The  sixth  nerve  is  close  to  the  carotid  artery — not  in  the  wall  of  the  sinus. 
Near  the  sphenoidal  fissure,  through  which  they  enter  the  orbit,  the 
relative  position  of  the  nerves  is  changed,  and  their  number  is  aug- 
mented, the  sixth  nerve  being  here  close  to  the  rest,  and  both  the  third 
and  ophthalmic  nerves  being  divided — the  former  into  two,  the  latter 
into  three  parts. 

In  the  sphenoidal  Assure. — The  fourth,  and  the  frontal  and  lachrymal 
branches  of  the  fifth,  which  are  here  higher  than  the  rest,  lie  on  the 
same  level,  the  first-named  being  the  nearest  to  the  inner  side;  and 
these  nerves  enter  the  orbit  above  the  muscles,  fig.  352.  In  entering 
the  same  cavity,  the  remaining  nerves  pass  between  the  heads  of  the 
outer  rectus  muscle : the  upper  division  of  the  third  being  highest,  the 
nasal  branch  of  the  fifth  next,  the  lower  division  of  the  third  beneadi 
these,  and  the  sixth  below  all. 

FOURTH  PAIR  OF  NERVES. 


The  fourth  (pathetic  nerve,  nervus  trochlearis,  n.  patheticus,  par 
quartum),  fig.  352,  *,  is  the  smallest  of  the  cranial  nerves,  and  is  dis- 
tributed only  to  the  upper  oblique  muscle  of  the  orbit.* 

From  the  remoteness  of  its  place 
Fig.  352.  qP  origin,  (see  p.  245,)  this  nerve 


The  nerves  in  Ihe  orbit  above  the  muscles, 
brought  into  view  by  removing  tlie  roof  of  the 
orbit  and  the  periosteum  (Arnold).  1.  Fifth 
nerve.  2,  Ophthalmic  branch  of  same  nerve. 
3, 'J'hird  uerve.  4,  Fourth  nerve.  5.  Optic  nerve. 
6.  Sixth  nerve,  a.  Internal  carotid  artery. 


has  a longer  extent  in  the  skull  than 
any  other  cranial  nerve.  It  has 
the  same  general  course  as  the  third 
in  the  wall  of  the  cavernous  sinus, 
and  through  the  sphenoidal  fissure. 
Before  reaching  the  sinus,  it  is  on 
a level  with  the  margin  of  the  ten- 
torium cerebelli,  by  the  side  of  the 
pons  Varolii ; and  it  enters  an  aper- 
ture in  the  free  border  of  the  ten- 
torium, outside  that  for  the  third 
nerve,  and  near  the  posterior  cli- 
noid  process.  Continuing  onwards 
through  the  outer  wall  of  the  caver- 
nous sinus,  the  fourth  nerve  enters 
the  orbit  by  the  sphenoidal  fissure, 
and  above  the  muscles.  Its  position 
with  reference  to  other  nerves  in 
this  part  of  its  course  has  been  al- 
ready referred  to  ((/.«.<«,  p.  261). 


* This  nerve  receives  its  name  from  entering  the  dura  mater  in  the  base  of  the  skull, 
next  to  the  third. 


FIFTH  PAIR  OF  NERVES. 


263 


While  in  its  fibrous  canal  in  the  outer  wall  of  the  sinus,  the  fourth 
nerve  is  joined  by  filaments  of  the  sympathetic,  and  not  unfrequently 
is  blended  with  the  ophthalmic  division  of  the  fifth.  Bidder  states 
that  some  offsets  are  here  given  from  it  to  the  dura  mater.* 

In  the  orbit,  fig.  352,  *,  the  fourth  nerve  inclines  inwards  above  the 
muscles,  and  finally  enters  the  orbital  surface  of  the  upper  oblique 
muscle. 

FIFTH  PAIR  OF  NERVES. 

The  fifth,  or  trifacial  nerve  (nerv.  trigeminus,  nerf  trifacial,  par 
quintum),.  fig.  353,  the  largest  cranial  nerve,  is  somewhat  analogous 
to  the  spinal  nerves.  It  is  a nerve  of  special  sense  (taste),  and  it  im- 
parts common  sensibility  (the  sense  of  touch)  to  the  face  and  the  fore 
part  of  the  head,  as  well  as  to  the  eye,  the  nose,  the  ear,  and  the 
mouth.  This  nerve,  moreover,  supplies  motor  filaments  to  the  mus- 
cles of  mastication. 

The  roots  of  the  fifth  nerve,  after  emerging  from  the  surface  of  the 
encephalon  {ante,  p.  245),  are  directed  forwards,  side  by  side,  to  the 


Fig.  353. 


A plan  of  the  branches  of  the  fifth  nerve,  modified  from  a sketch  by  Sir  C.  Bell.  a.  Snhmas- 
illary  gland,  with  the  submaxillary  ganglion  above  it.  1.  Small  root  of  Ihe  fifth  nerve,  which 
joins  the  lower  maxillary  division.  2.  Larger  root,  with  the  Gasserian  ganglion.  3.  Ophthalmic 
nerve.  4.  Upper  maxillary  nerve.  5.  Lower  maxillary  nerve.  6.  Chorda  tympani.  7.  Facial 
nerve. 


* Three  or  more  small  filaments  are  described  as  extending  in  the  tentorium  as  far  as 

the  lateral  sinus,  and  one  is  figured  as  joining  the  sympathetic  on  the  carotid  artery. 

Neurologische  Beohachtungen,  Von.  Dr.  F.  H.  Bidder,  Dorpat,  1836. 


264 


OPHTHALMIC  NERVE. 


midfile  fossa  of  the  skull,  through  an  aperture  in  the  dura  mater,*  on 
the  summit  of  the  petrous  part  of  the  temporal  bone.  Here  the  larger 
root  alters  in  appearance:  its  fibres  diverge  a little,  and  enter  a semi- 
lunar body,  the  Gasserian  ganglion ; whilst  the  smaller  root  passes 
beneath  the  ganglion,  without  being  united  in  any  way  to  it,  and  joins 
outside  the  skull  the  lowest  of  the  three  divisions  of  the  nerve  which 
issue  from  the  ganglion. 

The  ganglion  of  the  fifth  nerve  or  Gasserian  ganglion  (ganglion  semi- 
lunare  seu  Gasserianum)  occupies  a depression  on  the  upper  part  of 
the  petrous  portion  of  the  temporal  bone,  near  its  point,  and  is  cre- 
scentic in  form,  the  convexity  being  turned  forwards.  On  its  inner 
side  the  ganglion  is  joined  by  filaments  from  the  carotid  plexus  of  the 
sympathetic  nerve,  and,  according  to  some  anatomists,  it  furnishes 
from  its  back  part  filaments  to  the  dura  mater. 

From  the  fore  part,  or  convex  border  of  the  Gasserian  ganglion, 
proceed  three  large  branches.  The  highest  (first  or  ophthalmic  divi- 
sion) enters  the  orbit;  the  second,  the  upper  maxillary  nerve,  is  con- 
tinued forwards  to  the  face,  below  the  orbit ; and  the  third,  the  lower 
maxillary  nerve,  is  distributed  chiefly  to  the  ear,  the  tongue,  the  lower 
teeth,  and  the  muscles  of  mastication.  The  first  two  divisions  of  the 
nerve,  proceeding  wholly  from  the  ganglion,  confer  sensibility  on  the 
structures  in  which  they  ramify;  but  the  last,  in  addition  to  that  func- 
tion, gives  motor  branches  to  the  muscles  referred  to,  the  additional 
fibres  being  derived  from  the  smaller  root  which  is  joined  with  this 
part  of  the  nerve.  The  third  division  is  therefore  a compound  nerve, 
for  in  it  are  combined  motor  and  sensory  fibres.  This  part  of  the  fifth 
cranial  nerve  is  therefore  analogous  to  a spinal  nerve;  but  with  the 
difl'erence,  that  while  all  the  offsets  of  a spinal  nerve  are  believed  to 
partake  of  both  motor  and  sensory  fibres,  only  a portion  of  the  lower 
’maxillary  nerve  is  so  compounded,  the  motor  root  being  joined,  as  al- 
ready stated,  with  but  a part  of  the  fibres  emanating  from  the  ganglion. 

A.  OPHTHALMIC  NERVE. 

The  ophthalmic  nerve,  or  first  division  of  the  fifth  nerve,  (ramus 
quinti  paris  primus  vel  ophthalmicus,)  fig.  353,  ^ is  the  smallest  of  the 
three  offsets  from  the  Gasserian  ganglion.  It  is  a flat  fasciculus,  about 
an  inch  in  length,  and  is  directed  upwards  to  the  sphenoidal  fissure, 
where  it  ends  in  branches  which  continue  onwards  through  the  orbit. 
In  the  skull  this  division  of  the  fifth  nerve  is  contained  in  the  process 
of  the  dura  mater  bounding  externally  the  cavernous  sinus,  and  it  is 
here  joined  by  filaments  from  the  cavernous  plexus  of  the  sympathetic ; 
according  to  Arnold,  it  gives  recurrent  branches  to  the  tentorium 
cerebelli.f  The  fourth  nerve  frequently  communicates  by  a conside- 
rable branch  with  this  nerve. 

* [In  more  than  half  the  subjects  I have  examined,  I have  observed  a spiculum  of  bone  in 
the  doubled  edge  of  dura  mater  forming-  the  superior  margin  of  the  foramen,  and  crossing  the 
latter  like  a bridge,  apparently  having  for  its  object  the  removal  of  pressure  of  the  superin- 
cumbent brain  upon  the  fifth  nerve  as  it  passes  over  the  summit  of  the  petrous  portion  of 
the  temporal  bone. — J.  L.] 

t There  is  as  much  dilFerence  of  statement  among  modern  as  among  ancient  authorities 
respecting  nerves  to  the  dura  mater.  Bidder  delineates  branches  furnished  to  this  mern- 


LACHRYMAL  AND  FRONTAL  BRANCHES. 


265 


Neai'  the  orbit  the  ophthalmic  nerve  furnishes  from  its  inner  side 
the  nasal  branch,  and  then  divides  into  the  frontal  and  lachrymal 
branches.  These  offsets  are  transmitted  separately  through  the  sphe- 
noidal fissure,  and  are  continued  through  the  orbit  (after  supplying  a 
few  filaments  to  the  eye)  to  the  lachrymal  gland,  to  the  nose,  the  eye- 
lids, and  the  muscles  and  integument  of  the  forehead. 

1.  Lachrymal  Branch. 

The  lachrymal  branch,  fig.  352,  at  its  origin  is  external  to  the  fron- 
tal, and  is  contained  in  a separate  tube  of  dura  mater.  In  the  orbit 
it  courses  along  the  outer  part,  above  the  muscles,  to  the  outer  angle 
of  the  cavity.  When  near  the  lachrymal  gland,  the  nerve  has  a con- 
necting filament  with  the  orbital  branch  of  the  upper  maxillary  nerve, 
and  when  lying  in  close  apposition  with  the  gland,  it  gives  many  fila- 
ments to  this  and  to  the  conjunctiva.  Finally,  the  lachrymal  nerve 
penetrates  the  palpebral  ligament,  and  ends  in  the  upper  eyelid,  the 
terminal  ramifications  being  joined  by  the  facial  nerve.* * 

2.  Frontal  Branch. 

The  frontal  branch,  fig.  352,^  the  largest  offset  of  the  ophthalmic,  is, 
like  the  preceding  nerve,  above  the  tnuscles  in  the  orbit,  and  occupies  the 
middle  of  the  cavity,  being  between  the  elevator  of  the  upper  eyelid  and 
the  periosteum.  About  midway  between  the  base  and  summit  of  the 
orbit,  the  nerve  divides  into  branches  (supratrochlear  and  supraorbital), 
which,  after  emerging  at  the  fore  part  of  the  orbit,  supply  the  muscles 
and  integument  of  the  forehead  and  the  upper  eyelid. 

а.  The  internal  or  sup'atrochlear  branch,  fig.  352,  is  prolonged  to  the  point  at 
which  the  pulley  of  the  upper  oblique  muscle  is  fi.xed  to  the  orbit.  Here  it  gives 
downwards  a filament  of  connexion  to  the  infratrochlear  branch  of  the  nasal 
nerve,  and  issues  from  the  cavity  between  the  orbicular  muscle  of  the  lids  and 
the  bone.  In  this  last  position  filaments  are  distributed  to  the  upper  eyelid.  The 
nerve  next  pierces  the  orbicularis  palpebrarum  and  occipito-frontalis  muscles, 
furnishing  offsets  to  these  muscles  and  the  corrugator  supercilii,  and  after  ascend- 
ing on  the  forehead,  ramifies  in  the  integument. 

б.  The  external  or  supraorbital  branch,  fig.  353,  passes  through  the  notch  of  the 
same  name  to  the  forehead,  and  ends  in  muscular,  cutaneous,  and  pericranial 
branches ; while  in  the  notch,  this  nerve  distributes  filaments  {palpebral)  to  the 
upper  eyelid. 

The  muscular  branches  referred  to,  supply  the  ■ corrugator  of  the  eyebrow,  the 
occipito-frontalis,  and  the  orbicular  rrluscle  of  the  eyelids,  and  join  the  facial 
nen’e  in  the  last  muscle.  The  cutaneous  nerves,  among  which  two  (outer  and 
inner)  may  be  noticed  as  the  principal  branches,  are  placed  at  first  beneath  the 
occipito-frontalis.  The  outer  one,  the  larger,  perforates  the  tendinous  expansion 
of  the  muscle,  and  ramifies  in  the  scalp  as  far  back  as  the  lambdoidal  suture. 
The  inner  branch  reaches  the  surface  sooner  than  the  preceding  nerve,  and  ends 
' in  the  integument  over  the  parietal  bone.  The  pericranial  branches  arise  from  the 


brane  from  the  fourth  nerve.  Arnold  represents  the  nerves  as  coming  from  the  ophthalmic 
division  of  the  fifth.  Purkinje  supposes  them  to  be  derived  from  filaments  of  the  sympa- 
thetic  nerve  that  run  along  the  meningeal  arteries;  and  Valentin  states  that  they  emanate 
from  the  sympathetic  on  the  carotid  artery.  Mr.  Swan  says  that  the  sixth  nerve  “sends 
several  filaments  to  the  dura  mater  behind  the  Gasserian  ganglion.” 

* In  consequence  of  the  junction  which  occurs  between  tlie  ophthalmic  division  of  the 
fifth  and  the  fourth  nerve,  the  lachrymal  branch  sometimes  appears  to  be  derived  from 
both.^ — Mr.  Swan  considers  this  the  usual  condition  of  the  lachrymal  nerve, — A Demonstra- 
' tion  of  the  Nerves  of  the  Human  Body,  page  36.  London,  1834. 

VOL.  II.  23 


2GG 


NASAL  BKANCH. 


cutaneous  nerve  beneath  the  muscle,  and  end  in  the  pericranium  covering  the 
frontal  and  parietal  bones. 

3.  Nasal  Branch. 

The  nasal  branch  (r.  oculo-nasalis),  fig.  353,  which  is  more  deeply 
placed  than  either  of  the  other  branches  of  the  ophthalmic  nerve,  occu- 
pies a place  successively  in  the  cavities  of  the  orbit,  the  cranium,  and 
the  nose.  In  its  circuitous  course  this  nerve  has  many  and  varied 
connexions. 

Separating  from  the  first  division  of  the  fifth  nerve  in  the  wall  of 
the  cavernous  sinus,  the  nasal  nerve  enters  the  orbit  between  the  heads 
of  the  outer  rectus.  Within  the  orbit  it  inclines  inwards  over  the  optic, 
nerve,  beneath  the  elevator  of  the  upper  eyelid  and  the  upper  rectus 
muscle,  to  the  inner  wall  of  the  cavity.  In  this  oblique  course  across 
the  orbit  it  furnishes  a single  filament  to  the  lenticular  ganglion,  and 
two  or  three  (ciliary)  directly  to  the  eyeball ; and  at  the  inner  side  of 
the  cavity  it  gives  otf  a considerable  branch  (infratrochlear),  which 
leaves  the  orbit  at  its  fore  part.  After  furnishing  these  offsets,  the  nasal 
nerve  enters  the  anterior  of  the  two  foramina  in  the  inner  wall  of  the 
orbit,  and  passing  above  the  ethmoidal  cells,  appears  for  a short  space  in 
the  cranium.  Within  the  skull,  the  nerve  lies  in  a groove  on  the  edge 
of  the  cribriform  plate  of  the  ethmoid  bone,  by  which  it  is  conducted  to 
a special  aperture  at  the  side  of  the  crista  galli.  By  that  opening  it  is 
transmitted  to  the  roof  of  the  nasal  fossa,  where  it  ends  in  two  branches, 
one  of  which  (external  nasal)  reaches  the  integument  of  the  side  of 
the  nose,  and  the  other  (internal  nasal)  ramifies  in  the  pituitary  mem- 
brane. The  branches,  which  have  been  indicated  as  furnished  by  the 
nasal  nerve,  w'ill  now  be  referred  to  in  detail. 

a.  The  branch  to  the  lenticular  ganglion  (radix  longa  ganglii  ciliaris),  fig.  353, 
very  slender,  and  about  half  an  inch  long,  arises  generally  between  the  heads  of 
the  rectus.  This  small  branch  is  sometimes  joined  by  a filament  from  the  caver- 
nous plexus  of  the  sympathetic  or  from  the  upper  division  of  the  third  nerve ; it 
lies  on  the  outer  side  of  the  optic  nerve,  and  enters  the  upper  and  back  part  of  the 
lenticular  ganglion,  constituting  its  long  root. 

h.  The  long  ciliary  nerves,  fig.  354,  two  or  three  in  number,  are  situate  on  the 
inner  side  of  the  optic  nerve ; they  join  one  or  more  of  the  nerves  from  the  lenti- 
cular ganglion,  (short  ciliary,)  and  after  perforating  the  sclerotic  coat  of  the  eye, 
are  continued  between  it  and  the  choroid  to  the  ciliary  ligament  and  the  iris. 

c.  The  infratrochlear  branch,  fig.  353,  runs  forwards  along  the  inner  side  of  the 
orbit  below  the  upper  oblique  muscle,  and  receives  near  the  pulley  of  that  muscle 
a filament  of  connexion  from  the  supratrochlear  nerve.  The  branch  is  then  con- 
tinued below  the  irulley  (whence  its  name)  to  the  irmer  angle  of  the  eye,  and 
ends  in  filaments  w'hich  supply  the  orbicular  muscle  of  the  lids,  the  caruncula, 
and  the  lachrymal  sac,  as  well  as  the  integument  of  the  eyelids  and  side  of  the 
nose. 

In  the  cavity  of  the  nose  the  nasal  nerve  ends  by  dividing  into  the 
following  branches: — 

d.  The  branch  to  the  nasal  septum  (ramus  septi)  extends  to  the  lower  part  of  the 
partition  between  the  nasal  fossae,  supplying  the  pituitary  membrane  near  the 
fore  part  of  the  septum. 


OPHTHALMIC  GANGLION. 


267 


e.  The  external  branch  (r.  externus  seu  lateralis),  fig.  355,“  descends  in  a groove 
on  the  inner  surface  of  the  nasal  hone  ; and  after  leaving  the  nasal  cavity  between 
that  bone  and  the  lateral  cartilage  of  the  nose,  fig.  353,  it  is  directed  downwards 
to  the  tip  of  the  nose,  beneath  the  compressor  nasi  muscle.  While  within  the 
nasal  fossa,  this  branch  gives  two  or  three  filaments  to  the  fore  part  of  its  outer 
wall,  which  extend  as  far  as  the  lower  spongy  bone.  The  cutaneous  part  joins 
the  facial  nerve. 

Summary. — The  first  division  of  the  fifth  nerve  is  altogether  sensory 
in  function.  It  furnishes  branches  to  the  ball  of  the  eye  and  the 
lachrymal  gland  ; to  the  mucous  membrane  of  the  nose  and  eyelids; 
to  the  integument  of  the  nose  and  the  fore  part  of  the  head  ; and  to  the 
muscles  above  the  upper  half  of  the  circumference  of  the  orbit.  Some 
of  the  cutaneous  filaments  join  offsets  of  the  facial  nerve,  and  the  nerve 
itself  communicates  with  the  sympathetic. 


OPHTHALMIC  GANGLION. 


There  are  four  small  ganglionic  masses  connected  with  the  divisions 
of  the  fifth  nerve  : the  ophthal- 
mic ganglion  with  the  first  di- 
vision, Meckel’s  ganglion  with 
the  second,  and  the  otic  and 
submaxillary  ganglia  with  the 
third  division  of  the  nerve. 

These  several  bodies  receive 
sensory  nerves  from  the  fifth, 
motor  nerves  from  other 
sources,  and  twigs  from  the 
sympathetic ; and  the  nerves 
thus  joining  the  ganglia  are 
named  their  roots. 

The  ophthalmic  or  lenticular 
ganglion  (gang,  ophthalmicum, 
serailunare,  vel  ciliare),  fig.  354, 
serves  as  a centre  for  the  sup- 
ply of  nerves— motor,  sensory,  ^ representation  of  some  of  the  nerves  of  the  orbit, 
, •'  especially  to  show  the  lenticular  ganglion  (Arnold), 

and  sympathetic — to  the  eye-  l.  Ganglion  of  the  fifth.  2.  Ophthalmic  nerve.  3. 
ball.  It  is  a small  reddish  Upper  maxillary  4 Lower  maxillary.  5 Nasal 

, , . I 1 1 c I branch,  giving  the  long  root  to  the  lenticular  gan- 

DOdy,  situate  at  the  back  OI  the  glion.  6.  Third  nerve.  7.  Inferior  oblique  branch  of 


orbit,  between  the  outer  rectus  third  connected  with  the  ganglion  by  the  short 
, , , . root.  8.  Optic  nerve.  9.  Sixth  nerve.  10.  Sympa- 

muSCle  and  the  optic  nerve,  thetic  on  the  carotid  artery. 

and  generally  in  contact  with 

the  ophthalmic  artery.  Rounded,  or  somewhat  quadrangular  in  shape, 
it  is  joined  behind  by  offsets  from  the  fifth,  the  third,  and  the  sympa- 
thetic nerves  ; and  from  its  fore  part  proceed  ciliary  nerves  to  the  eye- 
ball.— From  the  quantity  of  fat  surrounding  the  ganglion,  it  is  not 
always  easy  to  detect  it. 


Union  of  the  ganglion  with  nerves : its  roots. — The  border  of  the  ganglion  directed 
backwards  receives  three  nerves.  One  of  these,  the  long  root,  fig.  354,  from  the 
nasal  branch  of  the  ophthalmic  trank,  joins  the  upper  part  (upper  angle)  of  this 
border.  Another  branch,  the  short  root,  fig.  354,  thicker  and  much  shorter  than 
the  preceding,  and  sometimes  divided  into  parts,  is  derived  from  the  branch  of 


268 


UPPER  MAXILLARY  NERVE. 


the  third  nen'e  supplied  to  the  lower  oblique  muscle^  and  is  connected  with  the 
lower  part  (lower  angle)  of  the  ganglion.  The  third  small  nerve,  lig.  354,  ema- 
nates from  the  cavernous  plexus  of  the  sympathetic,  and  reaches  the  ganglion  with 
the  long  upper  root ; or  these  two  nerves  may  be  inseparably  conjoined  before 
reaching  the  ganglion.* 

Branches  of  the  ganglion. — From  the  fore  part  of  the  ganglion  arise  ten  or  twelve 
delicate  filaments — the  short  ciliary  nerves,  fig.  354.  These  nerves  are  disposed 
in  two  fasciculi,  arising  from  the  upper  and  lower  angles  of  the  ganglion,  and 
they  run  forwards,  one  set  above,  the  other  beloW  the  optic  nerve,  the  latter 
being  the  more  numerous.  They  are  accompanied  by  filaments  from  the  nasal 
nerve  (long  ciliary),  with  which  some  are  joined.  Having  entered  the  eyeball 
by  apertures  in  the  back  part  of  the  sclerotic  coat,  the  nerves  are  lodged  in 
grooves  on  its  inner  surface ; and  at  the  ciliary  ligament,  which  they  pierce, 
(some  few  appearing  to  be  lost  in  its  substance,)  they  turn  inwards  and  ramify  i.i 
the  iris. 

B.  UPPER  MAXILLARY  NERVE. 

The  upper  maxillary  nerve,  or  second  division  of  the  fifth  cranial 
nerve  (ramus  quinti  paris  secundus,  v.  maxillaris  superior),  fig.  353,“, 
is  intermediate  in  size  and  situation  between  the  ophthalmic  and  lower 
maxillary  nerves. 

This  nerve,  named  from  its  connexion  with  the  upper  maxilla,  has 
an  almost  horizontal  direction,  in  great  part  through  that  bone,  to  the 
face.  It  commences  at  the  middle  of  the  Gasserian  ganglion,  present- 
ing at  its  origin  the  appearance  of  a flattened  band,  and  speedily  leaves 
the  skull  by  the  foramen  rotundum  of  the  sphenoid  bone,  having  pre- 
viously become  round  and  firm.  After  escaping  from  the  cavity  of 
the  skull  the  nerve  crosses  the  spheno-maxillary  fossa,  and  enters  the 
canal  in  the  floor  of  the  orbit  (in  the  orbital  plate  of  the  upper  max- 
illa), by  which  it  is  conducted  to  the  face.  As  soon  as  it  emerges 
from  the  infraorbital  foramen,  the  upper  maxillary  nerve  terminates 
beneath  the  elevator  of  the  upper  lip  in  branches  which  spread  out  to 
the  side  of  the  nose,  the  eyelid,  and  the  upper  lip. 

Branches. — In  the  spheno-maxillary  fossa  a branch  ascends  from 
the  upper  maxillary  nerve  to  the  orbit,  and  one  or  two  descend  to  join 
Meckel’s  ganglion,  and  to  be  distributed  to  the  nose  and  mouth. 
Whilst  the  nerve  is  in  contact  with  the  upper  maxilla,  it  furnishes 
dental  branches — one  on  the  tuberosity  of  the  bone,  the  other  at  its 
fore  part.  To  these  must  be  added  the  terminal  branches  already  in- 
dicated. 

1.  Orbital  Branch. 

The  orbital  or  temporo-malar  branch,  a small  cutaneous  nerve, 
enters  the  orbit  by  the  spheno-maxillary  fissure,  and  divides  into  two 
branches  (temporal  and  malar),  which  are  distributed,  as  their  names 
imply,  to  the  temple  and  the  prominent  part  of  the  cheek. 

a.  The  temporal  branch  is  contained  in  an  osseous  groove  or  canal  in  the  outer 
wall  of  the  orbit,  and  leaves  this  cavity  by  a foramen  in  the  malar  bone.  When 
about  to  traverse  the  bone,  it  is  joined  by  a communicating  filament,  (in  some 
cases,  two  filaments,)  from  the  lachrymal  nerve.  The  nerve  is  then  inclined  up- 
wards in  the  temporal  fossa  between  the  bone  and  the  temporal  muscle,  perfo- 

* Other  roots  have  been  assigned  to  the  ganglion.  See  a paper  by  Valentin  in  Muller  s 
Archiv  for  1840. 


BRANCHES  OF  THE  UPPER  MAXILLARY. 


269 


rates  the  temporal  aponeurosis  an  inch  above  the  zygoma,  and  ends  in  cutaneous 
filaments  over  the  temple.  The  cutaneous  ramifications  are  united  with  the 
facial  nerve,  and  sometimes  with  the  superficial  temporal  nerve  of  the  third  divi- 
sion of  the  fifth. 

b.  The  malar  branch  (r.  subcutaneus  malse),  lies  at  first  in  the  loose  fat  in  the 
lower  angle  of  the  orbit,  and  is  continued  to  the  face  through  a foramen  in  the 
malar  bone,  where  it  is  frequently  divided  into  two  filaments.  In  the  promi- 
nence of  the  cheek  this  nerve  communicates  with  the  facial  nerve. 

2.  Spheno-palatine  Branches. 

The  spheno-palatine  branches,  fig.  353,  two  in  number,  descending 
from  the  trunk  of  the  nerve  in  the  spheno-maxillary  fossa,  are  con- 
nected with  the  ganglionic  body  (Meckel’s  ganglion),  which  is  placed 
in  that  fossa,  and  are  distributed  to  the  nose  and  palate.  These 
branches  will  be  described  with  the  ganglion  referred  to. — (See  p. 
270.) 

3.  Posterior  Dental  Branches. 

The  posterior  dental  branches,  fig.  353,  two  in  number,  are  directed 
outwards  over  the  tuberosity  of  the  maxillary  bone. 

a.  One  of  the  branches  enters  a canal  in  the  bone  by  which  it  is 
conducted  to  the  teeth,  and  gives  forwards  a communicating  filament 
to  the  anterior  dental  nerve.  It  ends  in  filaments  to  the  molar  teeth 
and  the  lining  membrane  of  the  cavity  in  the  upper  maxillary  bone, 
and  near  the  teeth  joins  a second  time  with  the  anterior  dental  nerve. 

b.  The  anterior  of  the  two  branches,  lying  on  the  surface  of  the 
bone,  is  distributed  to  the  gums  of  the  upper  jaw  and  to  the  buccina- 
tor muscle. 

4.  Anterior  Dental  Branch. 

The  anterior  dental  branch,  leaving  the  trunk  of  the  nerve  at  a 
varying  distance  from  its  exit  at  the  infraorbital  foramen,  enters  a 
special  canal  in  front  of  the  antrum  of  Highmore.  In  this  canal  it 
receives  the  filament  from  the  posterior  dental  nerve,  and  divides  into 
two  branches,  which  furnish  offsets  for  the  front  teeth. 

a.  One  branch,  the  inner  one,  supplies  the  incisor  and  canine  teeth.  Filaments 
from  this  nerve  enter  the  lower  meatus  of  the  nose,  and  end  in  the  membrane 
covering  the  lower  spongy  bone. 

h-  The  outer  branch  gives  filaments  to  the  bicuspid  teeth,  and  is  connected  with 
the  posterior  dental  nerve. 

5.  Infraorbital  Branches. 

The  infraorbital  branches,  fig.  353,  which  are  large  and  numerous, 
spring  from  the  end  of  the  upper  maxillary  nerve  beneath  the  elevator 
muscle  of  the  upper  lip,  and  are  divisible  into  palpebral,  nasal,  and 
labial  sets. 

a.  The  palpebral  branch  (there  may  be  two  branches)  turns  upwards  to  the 
lower  eyelid  in  a groove  or  canal  in  the  bone,  and  supplies  the  orbicular  muscle; 
it  ends  in  filaments  which  are  distributed  to  the  lid  in  its  entire  breadth.  At  the 
outer  angle  of  the  eyelids  this  nerve  is  connected  with  the  facial  nerve. 

b.  The  nasal  branches  are  directed  inwards  to  the  muscles  and  integument  of  the 
side  of  the  nose,  and  they  communicate  with  the  cutaneous  branch  of  the  nasal 
nerve  furnished  by  the  first  division  of  the  fifth  nerve. 

23* 


270 


SPHENO-PALATINE  GANGLION. 


c.  The  labial  branches,  the  largest  of  the  terminal  branches  of  the  upper  max- 
illary nerve,  three  or  four  in  number,  are  continued  downwards  beneath  the  pro- 
per elevator  of  tlte  upper  lip.  Branching  out  as  they  descend,  these  nerves  are 
distributed  to  the  integument,  the  mucous  membrane  of  the  mouth,  the  labial 
glands,  and  the  muscles  of  the  upper  lip. 

Near  the  orbit  the  infraorbital  branches  of  the  upper  maxillary  nerve  are 
joined  by  branches  of  the  facial  nerve,  the  union  between  the  two  being  named 
infraorbital  plexus. 


SPHENO-PALATINE  GANGLION. 


The  spheno-palatine  ganglion,  commonly  named  Meckel’s  ganglion, 

fig.  355,  has  its  seat  on  the  sphe- 

Fig.  355. 

no-palatine  branches  of  the  upper 
maxillary  nerve,  and  is  deeply 
placed  in  a hollow  (spheno-max- 
illary  fossa)  between  the  ptery- 
goid process  of  the  sphenoid  bone 
and  the  upper  maxilla,  and  close 
to  the  spheno-palatine  foramen. 
It  is  of  a grayish  colour,  trian- 
gular in  form  or  heart-shaped, 
and  convex  on  the  outer  surface. 
The  gray  or  ganglionic  substance 
is  not  mixed  with  all  the  fibres  of 
the  spheno-palatine  branches  of 
the  upper  maxillary  nerve,  but  is 
placed  at  the  back  part,  at  the 
. . r L j r-A/T  I point  of  junction  of  the  sympa- 

A View  of  Ihe  olfaclory  nerve,  and  of  Meekers  \ i r i 

ganglion  seen  from  the  inner  side.  (From  thetlC  Of  deep  branch  OI  the 

Scarpa.)  a.  Elevator  muscle  of  the  soft  palate  vidian,  SO  that  the  SphenO-pala- 

thrown  down.  h.  Part  of  the  soft  palate,  c.  Body  . j*  ^ ..l 

of  the  sphenoid  bone.  d.  Internal  pterygoid  plate,  tine  nerveS  proceeding  tO  the 
1.  Bulb  of  the  olfactory  nerve,  giving  branches  ^ose  and  palate  pass  tO  their 

over  the  upper  two  spongv  bones.  2.  Nasal  , ‘ f . 

branch  of  the  ophthalmic  nerve.  3.  Smaller  destination  Without  being  in- 
palatine nerve.  4.  Meckel’s  ganglion.  5.  Larger  volved  in  the  ganglionic  mass. 
palatine  nerve,  dividing  in  the  roof  of  the  mouth.  -i  • ° t 

6.  Vidian  nerve.  7.  External  palatine  nerve.  Considering  the  ganglion  aS  a 

centre  from  which  offsets  pro- 
ceed, there  are  branches  from  it  directed  upwards  to  the  orbit,  some 
downwards  to  the  palate,  others  inwards  to  the  nose,  and  one  or  two 
pass  backwards  to  (or,  perhaps  better,  received  from)  the  sympathetic 
and  facial  nerves. 


1.  Ascending  Branches. 

The  ascending  branches,  very  small,  and  three  or  more  in  number, 
enter  the  orbit  by  the  spheno-inaxillary  fissure,  and  supply  the  peri- 
osteum.* 


2.  Descending  Branches. 

The  descending  branches,  continued  chiefly  from  the  spheno-palatine 

* Bock  describes  a branch  ascending  from  the  ganglion  to  the  sixth  nerve ; Tiedemann 
•one  to  the  lower  angle  of  the  ophthalmic  ganglion.  The  filaments  described  by  Hirzei  as 
ascending  to  the  optic  nerve,  most  probably  join  the  ciliary  nerves  which  surround  that 
(the  optic)  nerve. 


BRANCHES  OF  THE  SPHE NO-PALATINE  GANGLION. 


271 


branches  of  the  upper  nnaxillary  nerve  {ante,  p.  269),  are  the  palatine 
nerves  (large,  small,  and  external).  They  are  distributed  to  the  tonsil ; 
to  the  soft  palate — its  glandular  and  muscular  substance,  and  mucous 
membrane ; to  the  gums  and  glands  of  the  hard  palate  ; and  to  the 
mucous  membrane  of  the  nose. 

a.  The  larger  or  anterior  palatine  nerve,  fig.  355,®,  descends  , in  the  largest  palatine 
canal,  and  divides  in  the  roof  of  the  mouth  into  branches,  which  are  received 
into  grooves  in  the  hard  palate,  and  extend  forward  nearly  to  the  mcisor  teeth. 
In  the  mouth  it  suppHes  the  gums,  glandular  structure,  and  mucous  membrane  of 
the  hard  palate,  and  joins  in  front  with  the  naso-palatine  nerve.  When  entering 
its  canal,  this  palatine  nerve  gives  a nasal  branch  which  ramifies  on  the  middle 
and  lower  spongy  bones;  and  a little  before  leaving  the  canal,  another  branch  is 
supplied  to  the  membrane  covering  the  lower  spongy  bone  : these  are  infp-ior 
nasal  branches.  Opposite  the  lower  spongy  bone  springs  a small  branch,  which  is 
continued  to  the  soft  palate  in  a separate  canal  behind  the  tnmk  of  the  nerve. 

b.  The  smaller  or  posterior  palatine  branch,  fig.  355,®,  arising  near  the  preceding 
nerve,  enters,  together  with  a small  artery,  the  smaller  palatine  canal,  and  by 
this  it  is  conducted  to  the  soft  palate,  the  tonsil,  and  the  uvula.  According  to 
Meckel,  it  supplies  the  levator  palati  muscle. 

c.  The  external  palatine  nerve,  fig.  355, the  smallest  of  the  series,  courses  be- 
tween the  upper  maxilla  and  the  external  pterygoid  mirscle,  and  enters  the 
external  palatine  canal  between  the  maxiUary  bone  and  pterygoid  process  of  the 
palate  bone.  At  its  exit  from  the  canal  it  gives  hrwards  a branch  to  the  uvula, 
and  outwards  another  to  the  tonsil  and  palate.  Occasionally,  this  rrerve  is  alto- 
gether wanting. 

3.  Internal  Branches. 

The  internal  branches  furnished  from  the  ganglion  consist  of  the 
naso-palatine,  and  the  upper  and  anterior  nasal,  which  ramify  in  the 
lining  membrane  of  the  nose. 

a.  The  upper  anterior  nasal,  fig.  355,  are  very  small  branches,  and  enter  the 
back  part  of  the  nasal  fossa  by  the  spheno-palatine  foramen.  Some  few  are 
prolonged  to  the  posterior  and  upper  part  of  the  septum,  and  the  remamder 
ramify  in  the  membrane  covering  the  upper  two  spongy  bones,  and  in  that  lining 
the  posterior  ethmoid  cells. 

b.  The  naso-palatine  nerve  (nervus  naso-palatinus,*  nerve  of  Cotunnius),  (see 
wood-cut  in  the  description  of  the  nose,)  long  and  slender,  leaves  the  inner  side 
of  the  ganglion  with  the  preceding  branches,  and  after  crossing  the  roof  of  the 
nasal  fossa  is  directed  forwards  on  the  lower  part  of  the  septum  nasi,  between  the 
periosteum  and  the  pituitary  membrane,  towards  the  anterior  palatine  foramen. 
It  descends  to  the  roof  of  the  mouth  by  a separate  canal  f which  opens  below  in 
the  centre  of  the  anterior  palatine  foramen,  the  nerve  of  tire  right  side  being 
behind  its  fellow,  and  in  a distinct  canal  (Scarpa).  In  the  mouth  the  two  naso- 
palatine nerves  are  connected  one  with  the  other,  and  they  end  in  several  fila- 
ments ; these  are  distributed  to  the  papilla  behind  the  incisor  teeth,  and  commu- 
nicate with  the  great  palatme  nerve.  In  its  course  along  the  septum,  small 
filaments  are  furnished  from  the  naso-palatine  nerve  to  the  pituitary  membrane. J 

* This  nerve  was  so  named  by  Scarpa,  in  an  Essay  (with  engravings)  on  the  nerves  of 
the  nose,  published  in  1785.  {Annotationes  Anatomies,  lib.  ii.)  Scarpa  mentions,  that 
when  his  essay  was  prepared  for  the  press,  an  engraving,  containing  a representation  of 
this  nerve,  which  Cotunnius  had  caused  to  be  made  twenty-three  years  before,  was  shown 
him  by  Girardi.  The  engraving  had  not,  and  has  never  been  published.  It  is  stated  by 
John  Hunter,  that  he  dissected  the  nerve  as  early  as  1754,  and  repeatedly  used  the  prepa- 
ration of  it  in  his  anatomical  lectures.  Hunter  adds  that,  in  1782,  he  showed  his  drawings 
and  engravings  of  the  nerves  of  the  nose  to  Scarpa,  who  was  then  in  London. — See  “ Ob- 
servations on  certain  parts  of  the  Animal  Economy,"  London,  1786. 

t See  Osteology,  p.  63. 

t Scarpa  denies  the  existence  of  branches  on  the  septum.  Consult  also  Wrisbero-  “ De 
nervis  arterias  venasque  comitantibus.”  (.Comment.,  t.  i.,  p.  374.) 


272 


BRANCHES  OF  THE  SPHENO  PALATINE  GANGLION. 


4,  Posterior  Branches. 

The  offsets  directed  backwards  from  the  spheno-palatine  ganglion 
are  the  vidian  and  pharyngeal  nerves. 

a.  The  vidian  nerve  (nerv.  vidianus  v.  pterygoideus),  fig.  355,  ®,  is  so  named 
from  the  canal  of  the  sphenoid  bone  in  which  it  is  contained.  Supposing  this 
nerve  to  proceed  backwards,  as  is  customary  in  anatomical  works,  it  arises  from 
the  back  of  the  ganglion,  which  seems  to  be  prolonged  into  it,  courses  backwards 
through  the  vidian  canal,  and  after  emerging  from  this  divides  into  two  branches; 
one  of  these,  the  superficial  petrosal,  joins  the  facial  nerve,  while  the  other,  the 
carotid  branch,  communicates  with  the  sympathetic.*  Whilst  the  vidian  nerve  is 
in  its  canal,  it  gives  inwards  to  the  nose  some  small  branches,  the  uppe^-  posterior 
nasal,  which  supply  the  membrane  of  the  back  part  of  the  roof  of  the  nose  and 
septum,  as  well  as  the  membrane  covering  the  end  of  the  Eustachian  tube. 

The  separate  course  of  the  branches  resulting  from  the  division  of  the  vidian 
nerve  will  now  be  described, 

The  supcijkial  petrosal  branch,  fig.  357,2  enters  the  cranium  through  the  cartila- 
ginous substance  filling  the  foramen  lacerum  anterius  at  the  base  of  the  skull. 
Lying  then  on  the  outer  side  of  the  carotid  artery  and  beneath  the  Gasserian 
ganglion,  the  nerve  is  directed  backwards  in  a groove  on  the  petrous  portion  of 
the  temporal  bone  to  the  hiatus  Fallopii;  and  it  is  finally  continued  through  the 
hiatus  Fallopii  to  the  aqueduct  of  the  same  name,  where  it  joins  the  gangliform 
enlargement  of  the  facial  nerve. 

The  carotid  or  sympathetic  portion  of  the  vidian  nerve,  shorter  than  the  other,  is 
of  a reddish  colour  and  softer  texture.  Like  the  preceding  branch,  it  is  surrounded 
by  the  cartilaginous  substance  filling  the  aperture  (foramen  lacerum  anterius)  at 
the  point  of  the  petrous  portion  of  the  temporal  bone ; and  it  is  inclined  back- 
wards, also  on  the  outer  side  of  the  carotid  artery,  to  end  in  the  filaments  of  the 
sympathetic  surrounding  that  vessel. 

In  accordance  with  the  view  taken  of  the  ganglia  connected  with  the  fifth 
nerve  (p.  267),  the  parts  of  the  vidian  nerve,  above  described  as  directed  back- 
wards from  the  spheno-palatine  ganglion,  should  be  considered  as  beginning  from 
the  facial  nerve  and  the  carotid  plexus,  and  coursing  forwards  (either  separately 
or  after  being  united)  to  join  the  ganglion  and  constitute  two  of  its  roots,  the 
third  being  derived  from  the  spheno-palatine  nerves. 

h.  The  pharyngeal  nerve  is  inconsiderable  in  size,  and  instead  of  emanating 
directly  from  the  ganglion,  may  be  derived  altogether  from  the  vidian.  This 
branch,  when  a separate  nerve,  springs  from  the  back  of  the  ganglion,  enters  the 
pterygo-palatine  canal  with  an  artery,  and  is  lost  in  the  lining  membrane  of  the 
part  of  the  pharynx  behind  the  Eustachian  tube. 

Summary. — The  upper  maxillary  nerve,  with  Meckel’s  ganglion, 
supplies  the  integument  of  the  side  of  the  head,  and  the  muscles  and 
integument  of  the  lower  eyelid,  the  side  of  the  nose,  and  the  upper  lip. 
The  following  parts  likewise  receive  their  nerves  from  the  same  source, 
viz.,  the  upper  teeth,  the  lining  membrane  of  the  nose  and  upper  part 
of  the  pharynx,  of  the  antrum  of  Highmore,  and  of  the  posterior 
ethmoid  cells;  the  soft  palate,  tonsil,  and  uvula  ; and  the  glandular  and 
mucous  structures  of  the  roof  of  the  mouth. 

But  few  communications  take  place  with  other  nerves.  In  the  face 
the  upper  maxillary  nerve  joins  freely  with  the  facial  nerve;  it  is, 
moreover,  through  the  medium  of  Meckel’s  ganglion,  connected  with 
the  facial  nerve  by  the  superficial  petrosal  branch  of  the  vidian,  and 
with  the  sympathetic  by  the  carotid  branch  of  the  same  nerve. 

* The  vidian  nerve  is  here  described,  as  it  was  by  Meckel,  as  a single  cord,  dividing  into 
parts.  Some  anatomists  consider  the  petrosal  and  carotid  branches  as  quite  distinct  one 
from  the  other  in  tlieir  whole  length,  and  connected  only  by  being  contained  in  the  same 
fibrous  tube. 


LOWER  MAXILLARY  NERVE. 


273 


C.  LOWER  MAXILLARY  NERVE. 

The  lower  maxillary  nerve,  fig.  353,®,  is  the  third  and  largest  branch 
of  the  fifth  nerve.  It  furnishes  branches  to  the  tongue  (the  gustatory 
nerve),  to  the  external  ear,  to  the  lower  teeth,  and  to  the  muscles,  the 
mucous  membrane,  and  integuments  about  the  lower  maxillary  bone. 

This  nerve  is  made  up  of  two  portions,  which  are  unequal  in  size, 
the  larger  being  derived  from  the  Gasserian  ganglion,  and  the  smaller 
being  the  slender  motor  root  of  the  fifth  nerve.  These  two  parts  leave 
the  skull  by  the  oval  foramen  in  the  sphenoid  bone,  and  unite  imme- 
diately after  their  exit.  A few  lines  beneath  the  base  of  the  skull,  and 
under  the  external  pterygoid  muscle,  the  lower  maxillary  nerve  sepa- 
rates into  two  primary  divisions,  one  of  which  is  higher  and  smaller 
than  the  other.  From  these  divisions  the  branches  to  various  parts 
emanate  as  follows  : — 

The  small,  or  u'p'per  division,  receives  nearly  all  the  fibrils  of  the 
smaller  (motor)  root  of  the  fifth  nerve,  and  terminates  in  offsets  to  the 
temporal,  masseter,  buccinator,  and  pterygoid  muscles.  A few  of  the 
filaments  of  the  motor  root  are  applied  to  the  larger  division  of  the 
nerve,  and  are  conveyed  to  other  muscles,  viz.,  the  mylo-hyoid,  the 
tensor  of  the  membrane  of  the  tympanum,  and  the  circumfiexus  palati. 
The  branches  will  now  be  considered  individually. 

1.  Deep  Temporal  Branches. 

The  deep  temporal  branches  are  two  in  number,  one  being  placed 
near  the  back  part,  the  other  near  the  front  of  the  temporal  fossa,  and 
beneath  the  temporal  muscle,  to  which  both  are  distributed. 

a.  Vae  posterior  branch  (r.  temporalis  profundus  posterior)  is  of  small  size,  and  is 
sometimes  conjoined  with  the  masseteric  branch.  It  courses  upwards  in  a groove 
in  the  bone  above  the  external  pterygoid  muscle. 

b.  The  anterior  branch  (r.  temporalis  profundus  anterior)  is  placed  like  the  pre- 
ceduig  between  the  bone  and  the  pterygoid  muscle,  and  is  then  reflected  over  the 
crest  of  the  sphenoid  bone  to  the  fore  part  of  the  temporal  fossa.  It  is  frequently 
joined  with  the  buccal  nerve,  and  sometimes  with  the  other  deep  temporal 
branch. 

2.  Masseteric  Branch. 

This  branch  is  directed  outwards  also  above  the  external  pterygoid 
muscle,  and  has  an  almost  horizontal  course  in  front  of  the  articula- 
tion of  the  lower  maxillary  bone,  and  through  the  sigmoid  notch  of 
the  maxilla,  to  the  inner  surface  of  the  masseter  muscle.  It  ramifies 
in  the  muscle  nearly  to  its  lower  end.  When  the  nerve  passes  by  the 
articulation  of  the  lower  jaw,  it  gives  one  or  more  filaments  to  that 
joint,  and  occasionally  it  furnishes  a branch  to  the  temporal  muscle. 

3.  Buccal  Branch. 

The  buccal  branch  (r.  buccinatorius,  v.  buccinatorio-labialis) 
pierces  the  substance  of  the  external  pterygoid  muscle,  and  courses 
forwards  to  the  face  under  cover  of  the  ramus  of  the  lower  maxillary 
bone,  or  through  the  fibres  of  the  temporal  muscle.  On  the  buccinator 
muscle,  its  fibres  separate  into  two  branches,  which  will  be  presently 
noticed. 


274 


AURICULO  TEMPORAL  NERVE. 


From  the  buccal  nerve,  while  passing  through  the  pterygoid  mus- 
cle, is  given  a branch  (pterygoid)  to  that  muscle;  and  when  it  has 
passed  beyond  the  same  muscle,  two  or  three  ascending  oflsets  are 
furnished  to  the  temporal  muscle.  Under  the  ramus  of  the  maxilla  it 
gives  filaments  to  the  upper  part  of  the  buccinator  ; these  perforate  the 
fibres  of  the  muscle,  and  end  in  the  buccal  glands  and  the  mucous 
membrane  lining  the  inner  surface  of  the  muscle. 

a.  The  xipper  branch  of  the  two  into  which  the  buccal  nerve  divides  communi- 
cates with  the  facial  nerve  in  a plexus  around  the  facial  vein,  and  supplies  the 
integument  and  the  upper  part  of  the  buccinator  muscle. 

h.  The  lower  branch,  directed  to  the  angle  of  the  mouth,  forms,  like  the  upper 
one,  a plexus  around  the  facial  vein,  and  is  distributed  to  the  integument,  to  the 
buccinator  muscle  and  the  mucous  membrane  lining  it,  as  well  as  (according  to 
Meckel)  to  the  muscles  of  the  angle  of  the  mouth.* 

4.  Pterygoid  Branches. 

The  pterygoid  branches  are  two  in  number : one  for  each  of  the 
pterygoid  muscles. 

a.  The  external  pterygoid  branch  is  most  frequently  derived  from  the  buccal 
nerve.  It  may  be  a separate  offset  from  the  smaller  portion  of  the  lower  maxil- 
lary  nerve. 

The  nerve  of  the  internal  pterygoid  muscle,  fig.  356,  at  its  origin  is  closely  con- 
nected with  the  otic  ganglion,  and  enters  the  inner  or  deep  surface  of  the  muscle. 

The  lower  and  larger  division  of  the  lower  maxillary  nerve  divides 
into  three  parts,  viz.,  the  auriculo-temporal,  gustatory,  and  lower 
dental.  The  auriculo-temporal  soon  leaves  the  short  common  trunk, 
and  the  other  two  nerves  separate  one  from  the  other  afterwards,  at  a 
variable  distance  below  the  base  of  the  skull. 

1.  AUKICULO-TEMPORAL  NERVE. 

The  auriculo-temporal  nerve  (nerv.  temporalis  superficialis),  fig. 
353,  as  the  name  implies,  is  distributed  to  the  ear  and  the  temple. 

The  nerve  often  commences  by  two  roots,  between  which  may  be 
placed  the  middle  meningeal  artery.  It  is  directed  at  first  backwards, 
beneath  the  external  pterygoid  muscle,  to  the  inner  side  of  the  articu- 
lation of  the  jaw  ; and  then  changing  its  course,  turns  upwards  be- 
tween the  ear  and  the  joint,  where  it  is  covered  by  the  parotid  gland. 
Lastly,  emerging  from  beneath  the  parotid,  it  divides  into  two  tem- 
poral branches. 

Branches. — Besides  the  terminal  branches  just  referred  to,  the 
auriculo-temporal  nerve  furnishes  branches  to  the  ear,  the  temporo- 
maxillary  joint,  and  the  parotid  gland,  as  well  as  communicating  fila- 
ments to  other  nerves.  These  will  now  be  severally  noticed. 

a.  The  auricular  branches  are  two  in  number.  One  of  these,  the  lower  of  the 
two,  arising  behind  the  articulation  of  the  jaw,  distributes  branches  to  the  ear 
below  the  external  meatus;  and  other  filaments,  turning  round  the  internal 
maxillary  artery,  join  the  sympathetic  nerve. 

The  upper  auricular  branch,  leaving  the  nerve  in  front  of  the  ear,  enters  the  inte- 
gument covering  the  tragus  and  the  pinna  above  the  external  auditory  meatus. 
Both  auricular  nerves  are  confined  to  the  outer  surface  of  the  ear. — See  Nerves  of 
the  External  Ear. 

b.  Branches  communicating  vjith  the  facial  nerve,  and  the  otic  ganglion.  — The 

* “ De  quinto  pare  nervorum  cerebri,”  in  Ludwig. — “ Scriptores  Neurologici,”  t.  i. 


GUSTATORY  NERVE. 


275 


branches  which  join  the  facial  nerve,  commonly  two  in  number,  pass  forward 
around  the  carotid  artery.  The  filaments  to  the  otic  ganglion  arise  near  the  be- 
ginning of  the  auriculo-temporal  nerve. 

c.  Branches  to  the  meatus  auditorius  and  temporo-maxillary  articulation. — The  nerves 
to  the  meatus,  two  in  number,  spring  from  the  point  of  connexion  of  the  facial 
and  auriculo-temporal  nerves,  and  enter  the  interior  of  the  auditory  meatus  be- 
tween its  osseous  and  cartilaginous  parts.  One  or  two  filaments  sometimes  per- 
forate the  cartilage  and  are  lost  on  the  convex  surface  of  the  meatus.  The  nerve 
to  the  articulation  comes  from  the  preceding  branches,  or  directly  from  the  auri- 
culo-temporal nerve. 

d.  The  parotid  branches  are  given  from  the  nerve  while  it  is  covered  by  the 
gland. 

e.  Temporal  Branches. — One  of  these,  the  smaller  and  posterior  of  the  two,  sup- 
plies the  anterior  muscle  of  the  auricle,  and  distributes  filaments  to  the  upper 
part  of  the  pinna  and  the  integument  above  it.  The  anterior  temporal  branch  ex- 
tends with  the  superficial  temporal  artery  to  the  top  of  the  head,  and  ends  in  the 
integument.*  It  is  often  united  with  the  temporal  branch  of  the  upper  maxillary 
nerve. 

2.  GUSTATORY  NERVE. 

The  gustatory  nerve,  or  lingual  branch  of  the  fifth,  fig.  353,  has  an 
oblique  direction  inwards,  under  cover  of  the  lower  maxillary  bone, 
to  the  tongue. 

This  nerve  is  deeply  placed  in  the  whole  of  its  course,  and  has  the 
following  connexions  with  surrounding  parts.  At  first  it  is  beneath 
the  external  pterygoid  muscle  with  the  dental  nerve,  lying  to  the  inner 
side  of  that  nerve,  and  is  sometimes  united  to  it  by  a cord  which 
crosses  over  the  internal  maxillary  artery.  In  the  same  place  the  gus- 
tatory nerve  is  joined  at  a small  angle  by  the  chorda  tympani.  Next, 
it  is  placed  between  the  internal  pterygoid  musclef  and  the  lower 
maxilla  ; and  it  is  then  inclined  obliquely  inwards  to  the  side  of  the 
tongue,  over  the  upper  constrictor  of  the  pharynx,  (where  this  muscle 
is  attached  to  the  maxillary  bone,)  and  above  the  deep  portion  of  the 
submaxillary  gland.  Lastly,  the  nerve  is  continued  along  the  side  of 
the  tongue  to  its  apex,  lying  below  the  sublingual  gland  and  in  con- 
tact with  the  mucous  membrane  of  the  mouth. 

The  branches,  which  are  few,  leave  the  nerve  by  the  side  of  the 
tongue.  Some  supply  the  mijcous  membrane  of  the  mouth  and  the 
contiguous  salivary  glands;  some  enter  the  tongue  and  its  papillae; 
and  others  connect  the  gustatory  nerve  with  the  hypoglossal  nerve  and 
the  submaxillary  ganglion. 

a.  The  branches  to  the  submaxillary  ganglion  are  two  or  three  in  number.  (See 
Submaxillary  Ganglion.) 

b.  Those  which  are  connected  with  offsets  from  the  hypoglossal  nerve  form  a 
plexus  at  the  inner  border  of  the  hyoglossus  muscle. 

c.  The  branches  distributed  to  the  mucous  membrane  of  the  mouth  are  given 
from  the  nerve  by  the  side  of  the  tongue,  and  supply  the  gaims  also. 

d.  Some  delicate  filaments  are  likewise  distributed  to  the  substance  of  the  sub- 
lingual gland. 

The  lingual  or  terminal  branches  perforate  the  muscular  structure 
of  the  tongue,  and  divide  into  filaments,  which  are  continued  almost 
vertically  upwards  to  the  conical  and  fungiform  papillae.  Near  the 
tip  of  the  tongue  the  branches  of  the  gustatory  and  hypoglossal  nerves 
are  united. 

* Meckel  mentions  a communication  between  this  branch  and  the  occipital  nerve, 
t It  has  been  observed  by  Meckel  to  give  filaments  to  this  muscle  (op.  cit.) 


276 


LOWER  MAXILLARY  NERVE— SUMMARY. 


3.  INFERIOR  DENTAL  NERVE. 

The  inferior  dental  nerve  (maxillaris  inferior,  Meckel),  fig.  353,  is 
the  largest  of  the  three  branches  of  the  lower  maxillary  nerve.  It 
courses  forwards  through  the  lower  maxillary  bone,  and  terminates  on 
the  face. 

Before  the  nerve  enters  the  canal  in  the  lower  maxilla,  it  has  the 
same  relative  position  as  the  gustatory  nerve,  near  which  it  lies, — that 
is  to  say,  it  is  first  beneath  the  external  pterygoid  muscle,  and  then 
between  the  internal  pterygoid  and  the  ramus  of  the  lower  maxilla, 
but  separated  from  the  muscle  by  the  internal  lateral  ligament  of  the 
articulation.  Being  then  received  into  the  canal  appropriated  to  it 
and  the  dental  artery  in  the  bone  just  named,  the  nerve  is  conducted 
forwards  beneath  the  teeth,  to  which  it  gives  filaments,  as  far  as  the 
foramen  (mental)  in  the  side  of  the  bone.  Here  it  bifurcates : one 
part,  the  incisor  branch,  is  continued  onwards  within  the  bone  to  the 
middle  line;  the  other  (labial  branch)  escapes  by  the  foramen  to  the 
face. 

In  addition  to  the  branches  already  indicated,  the  dental  nerve, 
when  about  to  enter  the  foramen  on  the  inner  surface  of  the  ramus  of 
the  jaw',  gives  ofi'a  slender  offset,  the  mylo-hyoid  branch. 

a.  The  mylo-hyoid  branch  is  lodged  in  a groove  on  the  ir-er  surface  of  the 
ramus  of  the  raaxiUary  bone,  in  which  it  is  confined  by  fibre  membrane,  and 
is  distributed  to  the  dower  or  cutaneous  surface  of  the  mylo-hyoid  muscle  and  to 
the  anterior  belly  of  the  digastric  muscle.  Occasionally  one  or  two  filaments  of 
this  nerve  enter  the  submaxillary  gland. 

b.  The  dental  branches  supplied  to  the  molar  and  bicuspid  teeth  correspond  to 
the  number  of  the  fangs  of  those  teeth.  Each  branch  enters  the  hole  in  a fang, 
and  terminates  in  the  pulp  of  the  tooth. 

c.  The  incisor  branch  has  the  same  direction  as  the  trunk  of  the  nerve ; it  ex- 
tends to  the  middle  line  from  the  point  of  origin  of  the  labial  branch,  and  supplies 
nerves  to  the  canine  and  incisor  teeth. 

d.  The  labial  (mental?)  branch,  emerging  from  the  bone  by  the  foramen  on  its 
outer  surface,  divides  beneath  the  depressor  of  the  angle  of  the  mouth  into  two 
parts. 

One  of  these,  the  outer  division,  supplies  the  depressor  anguli  oris  and  orbicu- 
laris oris  muscles,  and  the  integument.  It  coTjt>^unicates  with  the  facial  nerve. 

The  inner  division,  the  larger  of  the  two,  ascends  to  the  lower  lip  beneath  the 
quadratus  menti  muscle,  to  which  it  gives  filaments  : the  greater  number  of  the 
branches  end  on  the  inner  and  outer  surfaces  of  the  lip.  These  (inner)  branches 
assist  but  slightly  in  forming  the  plexus  of  union  with  the  facial  nerve. 

Sicmmary. — The  lower  maxillary,  or  third  division  of  the  fifth,  is 
partly  a compound  nerve.  It  furnishes  a nerve  of  special  sense  to 
the  tongue  (the  gustatory  nerve).  Cutaneous  filaments  ramify  on  the 
side  of  the  head,  and  the  external  ear,  in  the  auditory  passage,  the 
lower  lip,  and  the  lower  part  of  the  face.  Branches  are  furnished  to 
the  mucous  membrane  of  the  mouth,  the  lower  teeth  and  gums,  the 
salivary  glands,  and  the  articulation  of  the  low'er  jaw. 

This  nerve  supplies  the  muscles  of  mastication  (viz.,  the  masseter, 
temporal,  and  two  pterygoid),  also  the  buccinator,  the  mylo-hyoid,  the 
circumflexus  palati,  -and  the  tensor  of  the  tympanum  ; and  the  smaller 
or  motor  part  of  the  fifth  nerve  being  distributed  among  the  branches 
furnished  to  these  muscles,  each  is  a compound  nerve.  The  muscles 
of  the  lower  lip  and  angle  of  the  mouth  likewise  receive  offsets  from 


OTIC  GANGLION. 


277 


the  lower  maxillary  nerve;  but  these  muscles  are  also  fui'nished  with 
branches  from  the  facial  nerve. 

The  gustatory  nerve  communicates  with  the  facial  nerve  through 
the  chorda  tympani,  and  with  the  hypoglossal  nerve  both  on  the  hyo- 
glossus  muscle  and  in  the  substance  of  the  tongue.  The  auriculo-tem- 
poral  nerve  is  connected  with  the  same  nerve  in  the  substance  of  the 
parotid  gland.  Lastly,  the  inferior  dental  joins  the  facial  nerve,  form- 
ing a large  plexus  in  which  the  nerves  are  freely  united  one  with  the 
other. 

Ganglia  connected  with  the  inferior  maxillary  nerve. — Two  small 
ganglia  (otic  and  submaxillary),  having  the  general  characters  and 
arrangement  ascribed  to  these  bodies  {ante,  page  267),  are  connected 
with  the  lower  maxillary  nerve : one  with  the  trunk  of  the  nerve,  the 
other  with  its  lingual  branch  (the  gustatory  nerve). 


Otic  Ganglion. 


The  otic  ganglion  (gang,  oticum  v.  auriculare, — Arnold),  fig.  356, 
of  a reddish  gray  colour. 


is  situate  on  the  deep  sur- 
face of  the  lower  maxillary 
nerve,  nearly  £6  . the  point 
of  junction  of  ie  motor 
fasciculus  with  that  nerve, 
and  around  the  origin  of 
the  internal  pteyvgoid 
branch.  Its  outer  side  is 
thus  in  contact  w'ith  the 
lower  maxillary  nerve ; its 
inner  surface  is  close  to 
the  cartilaginous  part  of 
the  Eustachian  tube  and 
the  circumflexus  palati 
muscle;  and  behind  it  is 


Fig.  356. 


the  middle  meningeal  ar- 
tery. 

The  nervous  filaments 
attached  to  this  ganglion 
are  divisible  into  those  by 
W'hich  it  is  connected  with 
nerves,  and  those  given  to  it  from  certain  muscles. 


The  otic  ganglion  seen  from  the  inner  side.  (From  Ar- 
nold.) a.  Internal  pterygoid  muscle,  b.  Carotid  artery 
with  the  sympathetic,  c.  Mastoid  process,  d.  Membrane 
of  tympanum,  e.  Bones  of  tympanum.  1.  Gasserian  gan- 
glion. 2.  First  division  of  fifth.  3.  Second  division.  4. 
Third  division.  5.  Branch  to  tensor  palati.  6.  Small  su- 
perficial petrosal  nerve.  7.  Chorda  tympani.  The  nerve 
of  the  internal  pterygoid  muscle  is  seen  on  the  muscle. 


Connexion  with  nerves — roots. — The  ganglion  is  connected  with  the  lower  max- 
illary nerve,  especially  with  the  branch  furnished  to  the  internal  pterygoid  muscle 
and  with  the  auriculo-temporal  nerve,  and  is  believed  thus  to  obtain  motor  and 
sensory  fibrils  or  roots;  it  is  brought  into  connexion  with  the  sympathetic  by  a 
filament  from  the  plexus  on  the  middle  meningeal  artery.  This  ganglion  has 
likewise  communication  with  the  glosso-pharjnigeal  and  facial  nerves  by  means 
of  the  small  petrosal  nerve  prolonged  to  it  from  the  tympanic  plexus. 

Branches. — Two  small  nerves  are  distributed  to  muscles-— one  to  the  tensor  of 
the  membrane  of  the  tympanum,  the  other  to  the  circumflexus  palati.  The  latter 
leaves  the  fore  part  of  the  ganglion ; the  former  is  directed  backwards  outside  the 
Eustachian  tube  to  the  osseous  canal  containing  the  muscle  for  which  it  is  des- 
tined. (See  the  figure.) 

VOL.  II. 


24 


278 


SEVENTH  PAIR  OF  NERVES. 


SubmaxOlary  Ganglion. 

The  submaxillary  ganglion  (ganglion  maxillare, — Meckel),  fig.  353, 
is  placed  above  the  deep  portion  of  the  submaxillary  gland,  and  is 
connected  by  filaments  with  the  gustatory  nerve.  It  is  about  the  size 
of  the  ophthalmic  ganglion.  By  the  upper  part  or  base  it  receives 
branches  from  nerves  (roots),  whilst  from  the  lower  part  proceed  the 
ofi’sets  which  are  distributed  from  the  ganglion. 

Connexion  with  nerves — roots. — A few  filaments  are  derived  from  the  gustatory 
nerve,  and  of  these  one  or  two  are  connected  with  both  the  fore  and  back  part  of 
the  ganglion.  The  ganglion,  it  is  believed,  also  receives,  at  its  back  part,  a 
branch  from  the  facial  nerve ; this  is  the  chorda  tympani,  prolonged  to  the  ganglion 
by  the  side  of  the  gustatory  nerve.  The  connexion  with  the  sympathetic  takes 
place  by  means  of  an  offset  from  the  filaments  on  the  facial  artery. 

Branches. — Some  nerves,  live  or  si.x  in  number,  radiate  to  the  substance  of  the 
submaxillary  gland.  Others  from  the  fore  part  of  the  ganglion,  longer  and  larger 
than  the  preceding,  end  in  the  mucous  membrane  of  the  mouth,  and  in  Wharton’s 
duct.* 

A diflerence  may  be  noticed  between  the  structures  to  which  the 
ganglia  above  described  furnish  offsets.  The  otic  ganglion  supplies 
muscles  exclusively,  while  the  submaxillary  ganglion  gives  no  mus- 
cular offsets. 

SIXTH  PAIR  OF  NERVES. 

The  sixth  cranial  nerve  (nerv.  abducens,  par  sextum),  fig.  351,  ^ is 
distributed  exclusively  to  the  outer  rectus  muscle  in  the  orbit,  and 
from  the  action  assigned  to  that  muscle,  it  is  sometimes  named  the 
“ abducent  nerve”  of  the  eyeball. 

From  the  point  of  origin,  the  nerve  courses  forwards  at  the  base 
of  the  skull,  through  the  cavernous  sinus  and  the  sphenoidal  fissure  to 
the  orbit.  It  enters  the  sinus  by  an  opening  in  the  dura  mater  behind 
the  body  of  the  sphenoid  bone,  but  is  separated  from  the  blood  by  the 
thin  lining  membrane.  In  the  sinus  this  nerve  lies  on  the  outer  side  of 
the  carotid  artery,  and  here  receives  one  or  two  filaments  of  commu- 
nication from  the  sympathetic.  In  entering  the  orbit  (between  the 
heads  of  the  external  rectus  muscle)  it  is  above  the  ophthalmic  vein. 
The  nerve  is  distributed  to  the  outer  rectus  by  two  or  three  filaments, 
which  pierce  the  ocular  surface  of  the  muscle.f 

SEVENTH  PAIR  OF  NERVES. 

In  the  seventh  cranial  nerve  of  Willis  are  combined  two  nerves 
having  a distinct  origin,  distribution,  and  function.  One  of  these 
(facial)  is  the  motor  nerve  of  the  face;  the  other  (auditory)  is  the 
special  nerve  of  the  sense  of  hearing.  Both  enter  the  internal  auditory 
meatus  in  the  temporal  bone,  but  they  are  soon  separated  one  from  the 
other. 

* According  to  Meckel  (“  De  quinto  pare,”  &c.),  a branch  occasionally  descends  in 
front  of  the  hyo-glossus  muscle,  and  after  joining  with  one  from  the  hypoglossal  nerve, 
ends  in  the  genio  hyo  glossus  muscle. 

+ The  sixth  nerve,  aceording  to  Bock  Beschreihung  des  Fuenfttn  Nervenpaares" — 
1817),  is  joined  in  the  orbit  by  a filament  from  Meckel’s  ganglion. 


BRANCHES  OF  THE  FACIAL  NERVE. 


279 


A.  FACIAL  NERVE. 

The  place  of  origin  of  the  facial  nerve  (nerv.  durus  paris  septimi, — 
Willis;  seventh  cranial  nerve, — Soemmerring)  has  been  mentioned  in 
connexion  with  the  account  given  of  the  nervous  centre.  Its  course 
being  tortuous  and  its  branches  numerous,  it  will  be  convenient  to 
divide  the  description  of  this  nerve  into  two  parts:  the  first  part  com- 
prising the  portion  w’hich  intervenes  between  the  origin  of  the  nerve 
and  its  entrance  into  the  parotid  gland ; the  second,  extending  to  the 
termination  of  the  nerve. 

THE  NERVE  FROM  ITS  ORIGIN  TO  THE  PAROTID  GLAND. 

From  its  place  of  origin,  the  facial  nerve  is  inclined  outwards  with 
the  auditory  nerve  to  the  internal  auditory  meatus.  The  facial  lies  in 
a groove  on  the  auditory  nerve,  and  the  two  are  united  in  the  auditory 
meatus  by  one  or  two  nervous  filaments.  At  the  bottom  of  the  meatus 
the  facial  nerve  enters  the  aqueduct  of  Fallopius,  and  follows  the 
windings  of  that  canal  to  the  surface  of  the  skull.  The  course  through 
the  temporal  bone  is  first  almost  horizontal  outw'ards,  between  the 
cochlea  and  vestibule,  to  the  inner  wall  of  the  tympanum,  and  it  is 
then  turned  suddenly  backwards  above  the  fenestra  ovalis  towards  the 
pyramid.  Where  it  bends,  the  nerve  presents  a reddish  gangliform 
enlargement  (intumescentia  ganglioformis),  which  marks  the  junction 
of  several  nerves.  Opposite  the  pyramid  it  is  arched  downwards  be- 
hind the  tympanum  to  the  stylo-mastoid  foramen,  by  which  it  leaves 
the  osseous  canal. 

Within  the  temporal  bone  the  facial  is  connected  with  several  other 
nerves  by  separate  branches;  and  immediately  after  issuing  through 
the  stylo-mastoid  foramen,  it  gives  off  three  small  branches, — viz.,  the 
posterior  auricular,  digastric,  and  stylo-hyoid  nerves.* 

1.  Connexions  with  other  Nerves. 

a.  Filaments  to  the  auditory  nerve. — In  the  meatus  auditorius  one  or  two  minute 
filaments  pass  between  the  facial  and  the  trunk  of  the  auditory  nerve. 

h.  Nerves  connected  with  the  gangliform  enlargement. — About  two  lines  from  the  be- 
ginning of  the  aqueduct  of  Fallopius,  where  the  facial  nerve  swells  into  a gan- 
gliform enlargement,  it  is  joined  by  the  large  superficial  petrosal  branch,  fig.  357,“ 
from  the  vidian  nerve.  To  the  same  enlargement  of  the  facial  nerve  are  likewise 
united  a filament  from  the  small  superficial  petrosal  nerve,  fig.  357®,  derived  from 
the  tympanic  nerve, f and  lastly,  the  external  superficial  petrosal  nerve,  fig.  357 
which  is  furnished  by  the  sympathetic  accompanying  the  middle  meningeal 
artery.f 

* Some  anatomists  describe  a branch  to  the  stapedius  muscle.  But  the  existence  of  a 
muscle,  and  therefore  of  the  nerve,  is  doubtful. 

+ Tliere  is  a difference  in  opinion  concerning  this  branch,  arising  from  its  smallness  and 
the  difficulty  of  determining  from  what  nerve  it  is  primarily  derived.  According  to  one 
opinion,  the  small  superficial  petrosal  nerve  is  the  continuation  to  the  otic  ganglion  of  the 
tympanic  nerve  (Jacobson’s),  and  is  united  by  a filament  to  the  enlargement  of  the  facial. 
According  to  another  manner  of  viewing  the  nerve,  it  begins  in  the  swelling  on  the  facial, 
connects  the  facial  with  the  otic  ganglion,  and  receives  only  a filament  of  union  from  Jacob- 
son’s nerve. 

t This  nerve,  named  and  described  by  Bidder,  enters  a canal  on  the  upper  surface  of  the 
petrous  portion  of  the  temporal  bone,  external  to  the  small  superficial  petrosal,  and  com- 
monly  joins  the  facial  beyond  the  swelling. 


280 


BRANCHES  OF  THE  FACIAL  NERVE. 


Fig.  357. 


This  drawing  represents  the  middle  fossa 
of  the  base  of  the  skull  with  the  petrous  part 
of  the  temporal  bone  cut  through  so  as  to 
expose  the  nerves  joining  the  facial  ; (from 
Bidder.) — a.  External  ear.  6.  Middle  fossa  of 
the  skull  with  the  middle  meningeal  artery 
branching  on  it.  1.  Facial  nerve  by  the  side 
of  the  auditory.  2.  Large  superficial  petrosal 
nerve.  3.  Small  superficial  petrosal  nerve  lying 
over  the  tensor  tympani  muscle.  4.  The  exter- 
nal superficial  petrosal  nerve.  5.  Chorda  tym- 
pani. 6.  Eighth  nerve. 

ing  to  some  anatomists,  joins  inseparabl 


c.  Filammts  from  the  auricular  branch 
of  the  pneumo gastric. — Near  the  exit  of 
the  facial  nerve  from  the  aqueduct  of 
Fallopius  it  is  joined  by  one  or  more 
of  these  filaments. 

2.  Chorda  Tympani. 

The  nerve  thus  named  leaves  the 
trunk  of  the  facial  nerve  below  the 
level  of  the  pyramid,*  and  crosses  the 
tympanum  to  join  the  gustatory  nerve, 
along  which  it  is  believed  to  be  con- 
ducted to  the  submaxillary  ganglion. 
After  passing  through  a short  canal  be- 
hind the  tympanum,  it  enters  that  cavity 
by  an  aperture  below  the  level  of  the 
pyramid,  and  close  to  the  ring  of  bone 
containing  the  membrane  of  the  tympa- 
num; and  being  invested  by  the  mucous 
lining  of  the  cavity,  it  is  directed  for- 
wards across  the  membrana  tympani 
and  the  handle  of  the  malleus  to  a fora- 
men at  the  inner  side  of  the  Glasserian 
fissure.  After  emerging  from  the  tym- 
panum through  the  opening  referred  to, 
the  nerve  lies  beneath  the  external  pte- 
rygoid muscle,  and  is  inclined  obliquely 
forwards  to  the  gustatory  nerve,  which 
it  meets  at  air  acute  angle.  Lastly, 
coursing  along  the  gustatory  nerve,  with 
which  it  is  connected  by  one  or  more 
filaments,  the  chorda  tympani  ends  in 
the  submaxillary  ganglion, — or,  accord- 
f with  that  nerve. 


3.  Posterior  Auricular  Branch. 

This  branch,  fig.  358,®  arises  close  to  the  stylo-mastoid  foramen:  it  turns  back- 
wards below  the  external  auditory  meatus,  and  is  joined  by  the  auricular  branch 
of  the  pneumogastric.  Arrived  in  front  of  the  mastoid  process,  it  divides  into  an 
auricular  and  an  occipital  portion  ; in  this  situation,  either  the  nerve  or  one  of  its 
branches  is  further  connected  with  the  great  auricular  nerve  of  the  cervical  plexus. 

The  auricular  division  sufiplies  fasciculi  to  the  retrahent  muscle  of  the  ear,  and 
ends  in  the  integument  on  the  posterior  aspect  of  the  auricle. 

The  occipital  branch  is  directed  backwards  beneath  the  small  occipital  nerve 
(from  the  cervical  plexus)  to  the  posterior  part  of  the  occipito-frontalis  muscle;  -t 
lies  close  to  the  bone,  and,  besides  supplying  the  muscle,  gives  upwards  fila- 
ments to  the  integument. 


4.  Digastric  and  Stylo-hyoid  Branches. 

The  digastric  branch  arises  in  common  with  that  for  the  stylo-hyoid  muscle,  and 
is  split  into  many  filaments,  which  enter  the  digastric  muscle : one  of  these,  after 
perforating  the  digastric,  joins  the  glosso-pharyngeal  nerve  near  the  base  of  the 
skull. 

The  stylo-hyoid  h-anch,  long  and  slender,  is  directed  inwards  from  the  digastric 
branch  to  the  muscle  from  which  it  is  named.  This  nerve  is  connected  with  the 
carotid  plexus  of  the  sympathetic  nerve. 

* Other  views  are  taken  of  the  origin  of  this  nerve.  Thus  it  is  said  to  arise  from  the 
gangliform  enlargement  of  the  facial,  and  to  accompany  this  nerve  to  the  foramen  by 
which  it  enters  the  tympanum  ; or,  that  it  is  only  a prolongation  from  the  huge  superficial 
petrosal  (Vidian),  which  courses  along  the  facial  nerve  without  joining  it,  and  becomes  the 
chorda  tympani. 


FACIAL  NERVE— ITS  DIVISIONS. 


281 


THE  FACIAL  NERVE  FROM  THE  STYLO-MASTOID  FORAMEN  TO  ITS  END. 


In  this  part  of  its  course 
the  facial  nerve  is  continued 
forwards  through  the  sub- 
stance of  the  parotid  gland, 
and  divides  in  the  gland, 
behind  the  ramus  of  the 
lower  maxilla,  into  two  pri- 
mary branches,  from  w'hich 
numerous  offsets  spread  out 
over  the  side  of  the  head, 
the  face,  and  the  upper  part 
of  the  neck.  The  two  pri- 
mary divisions  of  the  nerve 
are  named  temporo-facial 
and  cervico-facial : they  are 
at  first  flattened  and  subdi- 
vided. This  part  of  the 
nerve,  with  its  divisions,  is 
known  as  the  “ pes  anseri- 
nus.”* 

The  TEMPORO-FACIAL  DIVI- 
SION, the  larger  of  the  two, 
takes  the  direction  of  the 
trunk  of  the  facial  nerve 
through  the  parotid  gland. 
Its  ramifications  and  con- 
nexions with  other  nerves 
form  a network  over  the 
side  of  the  face,  extending 
as  high  as  the  temple,  and 
as  low  as  the  mouth.  These 
branches  are  arranged  into 
temporal,  malar,  and  infra- 
orbital sets. 

Near  its  commencement 
this  division  of  the  facial  is 
connected  with  theauriculo- 


[Fig.  358. 


The  distribution  of  the  facial  nerve  and  the  branches 
of  the  cervical  plexus.  1.  The  facial  nerve,  escaping 
from  the  stylo-mastoid  foramen,  and  crossing  the  ramus 
of  the  lower  jaw;  the  parotid  gland  has  b en  removed 
in  order  to  see  the  nerve  more  distinctly.  2.  The  pos- 
terior auricular  branch ; the  digastric  and  stylo-mastoid 
filaments  are  seen  near  the  origin  of  this  branch.  3. 
Temporal  branches,  communicating  with  (4)  the  branches 
of  the  frontal  nerve.  5.  Facial  branches,  communicat- 
ing with  (6)  the  infra  orbital  nerve.  7.  Facial  branches, 
communicating  with  (8)  the  mental  nerve.  9.  Cervico- 
facial branches,  communicating  with  (10)  the  superficia- 
lis  colli  nerve,  and  forming  a plextis  (11)  over  the  sub- 
maxillary gland.  The  distribution  of  the  branches  of 
the  facial  iti  a radiated  directionover  the  side  of  the  face 
and  their  looped  communications  constitute  the  pes 
anserinus.  12.  The  auricularis  magniis  nerve,  one  of 
the  ascending  branches  of  the  cervical  plexus.  13  "The 
occipitalis  minor,  ascending  along  the  posterior  border 
of  the  sterno-mastoid  muscle.  14.  The  superficial  and 
deep  descending  branches  of  the  cervical  plexus.  15. 
The  spinal  accessory  nerve,  giving  off  a branch  to  the 
external  surface  of  the  trapezius  muscle.  16.  The  oc- 
cipitalis major  nerve,  the  posterior  branch  of  the  second 
cervical  nerve. — W.] 


temporal  nerve  (of  the  fifth) 
by  one  or  two  filaments  which  turn  round  the  external  carotid  artery; 
and  it  gives  some  filaments  to  the  tragus  of  the  outer  ear. 


a.  The  temporal  branches  ascend  over  the  zygoma  to  the  side  of  the  head.  Some 
end  in  the  anterior  muscle  of  the  auricle,  and  the  integument  of  the  temple,  and 
communicate  with  the  temporal  branch  of  the  upper  maxillary  nerve  near  the 
ear,  as  well  as  with  (according  to  Meckel)  the  auriculo-temporal  branch  of  the 
lower  maxillary  nerve.  Other  branches  enter  the  occipito-frontalis,  and  the 
orbicular  muscle  of  the  eyelids,  and  join  offsets  from  the  supraorbital  branch  of 
the  ophthalmic  nerve. 

b.  The  malar  branches  cross  the  malar  bone  to  the  outer  angle  of  the  orbit,  and 

* The  designation  appears  to  have  originated  in  a comparison  made  by  Winslow. 

24* 


282 


AUDITORY  NERVE. 


supply  the  orbicular  muscle  and  the  corrugator  of  the  eyebrow.  Some  filaments 
are  distributed  to  both  the  upper  and  the  lower  eyelid : those  in  the  upper  eyelid 
join  filaments  from  the  lachrymal  and  supraorbital  nerves ; those  in  the  lower 
lid  are  connected  with  filaments  from  the  upper  maxillary  nerve.  Filaments  from 
this  series  communicate  with  the  malar  branch  (r.  subcutaneus  malaj)  of  the  upper 
maxillary  nerve. 

c.  The  infraorbital  branches,  of  larger  size  than  the  other  branches,  are  almost 
horizontal  in  direction,  and  are  distributed  between  the  orbit  and  mouth.  They 
supply  the  buccinator  and  orbicularis  oris  muscles,  the  elevators  of  the  upper  lip 
and  angle  of  the  mouth,  and  likewise  the  integument.  Numerous  communica- 
tions take  place  with  the  fifth  nerve.  Beneath  the  elevator  of  the  upper  lip  these 
nerves  are  united  in  a plexus  with  the  branches  of  the  upper  maxillary  nerve ; on 
the  side  of  the  nose  they  communicate  with  the  nasal,  and  at  the  inner  angle  of 
the  orbit  with  the  infratrochlear  nerve.  The  lower  branches  of  this  set  are  con- 
nected with  the  cervico-facial  division. 

The  cEiivico-FACiAL  DIVISION  of  the  facial  nerve  is  directed  obliquely 
through  the  parotid  towards  the  angle  of  the  lower  jaw,  and  gives 
branches  to  the  face,  below  those  of  the  preceding  division,  and  to  the 
upper  part  of  the  neck.  The  branches  are  named  buccal,  supramax- 
illary,  and  inframaxillary.  In  the  gland  this  division  of  the  facial  nerve 
is  joined  by  filaments  of  the  great  auricular  nerve  of  the  cervical  plexus, 
and  offsets  from  it  enter  the  substance  of  the  gland. 

a.  The  buccal  branches  communicate  with  the  temporo-facial  division,  cross  the 
masseter  muscle,  and  join  on  the  buccinator  muscle  with  filaments  of  the  buccal 
branch  of  the  lower  maxillary  nerve. 

b.  The  supramaxillary  branch,  fig.  358,  sometimes  double,  gives  an  offset  over 
the  side  of  the  maxilla  to  the  angle  of  the  mouth,  and  is  then  directed  inwards, 
beneath  the  depressor  of  the  angle  of  the  mouth,  to  the  muscles  and  integument 
between  the  lip  and  chin ; it  joins  with  the  labial  branch  of  the  lower  dental 
nerve. 

c.  The  inframaxillary  branches  (r.  subcutanei  colli),  fig.  358,  perforate  the  deep 
cervical  fascia,  and,  placed  beneath  the  platysma  muscle,  form  arches  across  the 
side  of  the  neck  as  low  as  the  hyoid  bone.  Some  branches  join  the  superficial 
cervical  nerve  beneath  the  platysma,  others  enter  that  muscle,  and  a few  perforate 
it  to  end  in  the  integument. 

Summary. — The  facial  nerve  is  the  motor  nerve  of  the  face.  It  is 
distributed  to  the  muscles  of  the  ear  and  of  the  scalp ; to  those  of  the 
mouth,  nose,  and  eyelids ; and  to  the  cutaneous  muscle  of  the  neck 
(platysma).  It  likewise  supplies  branches  to  the  integument  of  the 
ear,  of  the  side  and  back  of  the  head,  as  well  as  to  that  of  the  face, 
and  the  upper  part  of  the  neck. 

This  nerve  is  connected  freely  with  the  three  divisions  of  the  fifth 
nerve,  and  with  the  submaxillary  and  spheno-palatine  ganglia;  with 
the  glosso-pharyngeal  and  pneumogastric  nerves ; with  the  auditory, 
the  sympathetic,  and  the  spinal  nerves. 

B.  AUDITORY  NERVE. 

The  auditory  nerve  (nervus  mollis  paris  septimi, — Willis,  eighth 
cranial  nerve  of  Soemmerring)  is  the  special  nerve  of  the  sense  of 
hearing,  and  is  distributed  exclusively  to  the  internal  ear. 

As  the  auditory  nerve  is  inclined  outwards  from  its  connexion  with 
the  medulla  oblongata  to  gain  the  internal  auditory  meatus,  it  is  in 
contact  with  the  facial  nerve,  but  a small  arterial  branch  destined  for 
the  internal  ear  partially  separates  them.  Within  the  meatus  the  two 


GLOSSO-PHARYNGEAL  NERVE. 


283 


nerves  are  connected  one  to  the  other  by  one  or  two  small  filaments. 
Finally  the  auditory  nerve  bifurcates  in  the  meatus:  one  of  the  parts 
is  the  nerve  of  the  cochlea  ; the  other  enters  the  vestibule  of  the 
internal  ear.  The  distribution  of  these  branches  will  be  described  with 
the  ear. 

EIGHTH  PAIR  OF  NERVES. 

The  eighth  cranial  nerve  is  composed  of  three  distinct  nerves — 
the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory.  Besides 
issuing  from  the  skull  by  the  same  foramen,  these  nerves  have  but 
little  in  common.  Two  of  them,  the  glosso-pharyngeal  and  pneumo- 
gastric, are  attached  to  the  medulla  oblongata  in  the  same  line,  and 
resemble  one  another  somewhat  in  their  distribution,  for  both  are  dis- 
tributed to  the  beginning  of  the  alimentary  canal.  But  the  other, 
the  spinal  accessory,  takes  its  origin  from  the  spinal  cord,  and  is 
distributed  exclusively  to  muscles. 

A.  GLOSSO-PHARYNGEAL  NERVE. 

The  glosso-pharyngeal  nerve  (one  division  of  the  eighth  pair,  ninth 
cranial  nerve  of  Soemmerring),  fig.  361,S  is  destined,  as  the  name 
implies,  for  the  tongue  and  pharynx. 

This  small  nerve  is  directed  outwards  from  its  place  of  origin  over 
the  flocculus  to  the  foramen  lacerum  jugulare,  through  which  it  leaves 
the  skull  with  the  pneumogastric  and  spinal  accessory  nerves,  but  in 
a separate  tube  of  dura  mater.*  In  passing  through  the  foramen, 
where  it  is  placed  somewhat  in  front  of  the  other  nerves,  this  nerve  is 
contained  in  a groove,  or  in  a canal  in  the  lower  border  of  the  petrous 
portion  of  the  temporal  bone,  and  presents,  successively,  two  ganglionic 
enlargements, — the  jugular  ganglion,  and  the  petrous  ganglion. 

In  the  neck  the  glosso-pharyngeal  nerve  is  very  deeply  placed  at 
its  commencement,  but  less  so  towards  its  termination.  After  leaving 
the  skull,  it  soon  appears  between  the  internal  carotid  artery  and  the 
jugular  vein ; and  in  its  course  to  the  tongue  and  pharynx  is  at  first 
directed  downwards  over  the  carotid  artery  and  beneath  the  styloid 
process  and  the  muscles  connected  with  the  process,  to  the  lower 
border  of  the  stylo-pharyngeus  muscle.  Here,  changing  its  direction, 
the  nerve  curves  inwards  to  the  tongue,  forming  an  arch  on  the  side 
of  the  neck.  In  this  last  part  of  its  course,  it  is  placed  on  the  stylo- 
pharyngeus  and  the  middle  constrictor  muscle  of  the  pharynx,  above 
the  upper  laryngeal  nerve ; and  near  the  tongue  it  is  beneath  the  hyo- 
glossus  muscle,  where  it  ends  in  offsets  distributed  to  the  pharynx,  the 
tonsil,  and  the  tongue. 

H\\Q  jugular  ganglion^  (gang-  superius  vel  jugulare),  fig.  .361,*  the 
smaller  of  the  tw'O  ganglia  of  the  glosso-pharyngeal  nerve,  is  situate 

* The  jugular  foramen  has  two  projecting  points  of  bone  for  the  attachment  of  separate 
portions  of  the  dura  mater.  Thus  the  foramen  is  divided  into  three  parts : one  in  front  for 
the  lower  petrosal  sinus,  one  behind  for  the  lateral  sinus,  and  a central  one  for  the  three 
nerves, 

t This  ganglion  was  known  to  Ehrenritter,  but  it  has  been  particularly  described  by 
Muller. — See  “ Medicinische  Zeitung  herausgegeben  von  dem  Verein  fur  Heilkunde  in 
Preussen.”  Berlin,  1S33;  and  Muller’s  “Archiv  f.  Anat.  u.  Physiol.,”  1834  and  1837. 


284 


TYMPANIC  BRANCH. 


at  the  upper  part  of  the  osseous  groove  in  which  the  nerve  is  laid 
during  its  passage  through  the  jugular  foramen.  Its  length  is  from 
half  a line  to  a line,  and  the  breadth  from  half  to  three-fourths  of  a 
line.  It  is  placed  on  the  outer  side  of  the  trunk  of  the  nerve,  and 
involves  only  some  of  the  fibres, — a small  fasciculus  passing  by  the 
ganglion,  and  joining  the  nerve  below  it. 

The  -petrous  ganglion  (ganglion  inferius  vel  petrosum, — Andersch), 
fig.  3G1,®  is  contained  in  a hollow  in  the  lower  border  of  the  petrous 
part  of  the  temporal  bone,  (receptaculurn  ganglioli  petrosi),  and 
measures  about  three  lines  in  length.  This  ganglion  includes  all  the 
filaments  of  the  nerve,  and  resembles  the  gangliform  enlargement  of 
the  facial  nerve.  From  it  arise  the  small  branches  by  which  the 
glosso-pharyngeal  is  connected  with  other  nerves  at  the  base  of  the 

skull : these  are  the  tympanic 
Fig-  359.  nerve,  and  branches  to  join 

the  pneumogastric  and  sym- 
pathetic. 

The  branches  of  the  glosso- 
pharyngeal nerve  are  divisible 
into  two  series;  in  the  first 
will  be  ranged  those  derived 
from  the  petrous  ganglion, 
and  serving  chiefly  to  connect 
this  nerve  with  others;  and 
the  second  will  comprise  the 
nerves  distributed  from  it  in 
the  neck. 


A drawing  of  the  tympanic  nerve  from  Breschet’s 
work  on  the  ear.  A Squamous  part  of  temporal  bone. 
B.  Petrous  portion  of  same.  c.  Lower  maxillary  nerve. 
D.  Internal  carotid  artery,  a.  Tensor  tympani  muscle. 
1.  Carotid  plexus.  2.  Otic  ganglion.  3.  Glosso-pha- 
ryngeal nerve.  4.  Tympanic  nerve.  5.  Branches  to 
carotid  plexus.  6.  Branch  to  fenestra  rotunda.  7. 
Branch  to  fenestra  ovalis.  8.  Branch  to  join  the  large 
superficial  petrosal  nerve.  9.  Small  superficial  petro- 
sal nerve.  10.  Nerve  to  tensor  tympani  muscle.  11. 
Facial  nerve.  12.  Chorda  tympani.  13.  Petrous  gan- 
glion of  the  glosso-pharyngeal.  14.  Branch  to  the 
membrane  lining  the  Eustachian  tube. 

glion,  and  is  conducted  to  the  tympanum  by 
of  the  temporal  bone.  On  the  inner  wall  of 


CONNECTING  BRANCHES,  AND  TYMPA- 
NIC BRANCH. 

1.  From  the  petrous  ganglion 
spring  three  smaU  filaments : — One 
passes  to  the  auricular  branch  of 
the  pneumogastric,  one  to  the 
upper  ganglion  of  the  sympa- 
thetic, or  vice  versa,  and  a third  to 
the  ganglion  of  the  root  of  the 
pneumogastric.  The  last  is  not 
very  constant. 

2.  The  branch  to  or  from  the  ja- 
cial  nerve  perforates  the  digastric 
muscle:  it  is  connected  with  the 
trunk  of  the  glosso-pharyngeal  be- 
low the  petrous  ganglion.* 

3.  The  tympanic  branch  (nerve  of 
Jacobson ; r.  tympanicus),  fig. 
359, ■*  arises  from  the  petrous  gan- 

a special  canalf  in  the  petrous  part 
the  tympanum,  fig.  359,  the  nerve 


* There  is  sometimes  another  branch  to  the  trunk  of  the  pneumogastric. 
t The  orifice  of  this  canal  is  in  the  ridge  of  bone  between  the  jugular  fossa  and  the 
carotid  foramen;  and  the  canal  is  directed  upwards  to  the  inner  wall  of  the  tympanum. 
From  it  three  channels  branch  off : one  bends  down  to  the  carotid  canal;  a second  ascends 
to  the  hiatus  Fallopii ; and  the  third  reaches  the  upper  part  of  the  petrous  portion  of  the 
temporal  bone,  external  to  the  hiatus  Fallopii. 


PNEUMOGASTRIC  NERVE. 


285 


joins  with  an  offset,'  from  the  sympathetic  in  a plexus  (tympanic),  and  distributes 
filaments  to  the  membrane  lining  the  tympanum  and  the  Eustachian  tube,  as 
well  as  one,”  to  the  fenestra  rotunda,  and  another,'  to  the  fenestra  ovalis. 

From  the  tympanic  nerve  are  given  three  connecting  branches,  by  which  it  com- 
municates with  other  nerves ; these  occupy  the  channels  continued  from  the 
osseous  canal,  through  which  the  nerve  enters  the  tympanum.  One  branch 
enters  the  carotid  canal  and  joins  with  the  sympathetic  on  the  carotid  artery.* 
A second,  fig.  359,®,  is  united  to  the  large  superficial  petrosal  nerve,  as  this  lies 
in  the  hiatus  Fallopii.  And  the  third,  fig.  359,9,  is  directed  upwards,  beneath 
the  canal  for  the  tensor  tympani  muscle,  towards  the  surface  of  the  petrous  por- 
tion of  the  temporal  bone,  where  it  becomes  the  small  superficial  petrosal  nerve, \ 
and  under  this  name  is  continued  to  the  exterior  of  the  skull  through  a small 
aperture  in  the  sphenoid  and  temporal  bones,  to  end  in  the  otic  ganglion.  As 
this  petrosal  nerve  passes  by  the  gangliform  enlargement  of  the  facial,  it  has  a 
connecting  filament  with  that  enlargement.! 

BRANCHES  DISTRIBUTED  IN  THE  NECK. 

1.  The  carotid  branches  course  along  the  internal  carotid  artery,  and  unite  with 
the  pharyngeal  branch  of  the  pneumogastric  and  with  branches  of  the  sympa- 
thetic. 

2.  The  pharyngeal  branches,  three  or  four  in  number,  unite  opposite  the  middle 
constrictor  of  the  pharynx  with  branches  of  the  pneumogastric  and  sympathetic 
to  form  the  pharyngeal  plexus.  Nerves  to  the  mucous  membrane  of  the  pharynx 
perforate  the  muscles,  and  extend  upwards  to  the  base  of  the  tongTie  and  the  epi- 
glottis, and  downwaras  nearly  to  the  hyoid  bone. 

3.  The  muscular  tranches  are  given  to  the  stylo-pharyngeus  and  constrictor  mus- 
cles. ^ 

4.  Tonsillitic  branches.  When  the  glosso-pharyngeal  nerve  is  near  the  tonsil^ 
some  branches  are  distributed  on  this  body  in  a kind  of  plexus  (circulus  tonsilla- 
ris). From  these  nerves,  offsets  are  sent  to  the  soft  palate  and  the  isthmus  of  the 
fauces,  where  they  join  the  palatine  nerves. 

5.  Lingual  h-anches.  The  glosso-pharyngeal  nerve  divides  into  two  parts  at  the 
border  of  the  tongue.  One  turns  to  the  upper  surface  of  the  tongue,  supplying 
the  mucous  membrane  at  its  base ; the  other  perforates  the  muscular  structure, 
and  ends  in  the  mucous  membrane  as  far  forwards  as  the  papillse  circumvallatsB, 
and  filaments  enter  those  papillse. 

Summary.  — The  glosso-pharyngeal  distributes  branches  to  the 
mucous  membrane  of  the  tongue  and  pharynx.  The  muscles  sup- 
plied by  it  are  some  of  those  of  the  pharynx  and  base  of  the  tongue. 
It  is  connected  with  the  following  nerves,  viz., — the  lower  maxillary 
division  of  the  fifth,  the  facial,  the  pneumogastric  (the  trunk  and 
branches  of  this  nerve),  and  the  sympathetic. 

B.  PNEUMOGASTRIC  NERVE. 

The  pneumogastric  nerve  (nervus  vagus,  par  vagum,  sympatheticus 
medius,  a division  of  the  eighth  pair  of  Willis,  tenth  cranial  nerve, — 
ScEmmerring),  fig.  360,“,  has  the  longest  course  of  any  of  the  cranial 

* Or  this  filament  may  be  said  to  spring  from  the  carotid  plexus,  and  join  Jacobson’s 
nerve  in  the  tympanic  plexus. 

t Bidder  always  found  the  small  superficial  petrosal  nerve  in  an  osseous  canal — never 
on  the  surface  of  the  bone.  This  observer  states,  too,  that  the  nerve  passes  from  the  skull 
through  the  sphenoid  bone  and  the  petrous  portion  of  the  temporal. — “ Neurologische  Beo- 
lachtungen.” 

t Jacobson  described  an  anterior  or  internal  branch  given  from  the  tympanic  nerve  to 
the  spheno-palatine  ganglion. 

§ An  additional  muscular  nerve  to  the  digastric  and  stylo  hyoid  muscles  is  noticed  by 
Cruveilhier. — Anat.  Descrip,  t.  iv.  It  is  probable  that  this  nerve  is  but  the  connecting 
branch  between  the  facial  and  glosso-pharyngeal  nerves. 


286 


PNEUMOGASTRIC  NERVE, 


nerves.  It  extends  through  the  neck  and  the  cavity  of  the  chest  to  the 
upper  part  of  the  abdomen;  and  it  supplies  nerves  to  the  organs  of 
voice  and  respiration,  to  the  alimentary  canal  as  far  as  the  stomach, 
and  to  the  heart.  ’ 

The  nerve  from  its  origin  to  the  thorax. — The  filaments  by  which 
this  nerve  arises  from  the  medulla  oblongata  are  collected  together,  so 
as  to  give  rise  to  a flat  fasciculus,  which  is  directed  over  the  flocculus 
to  the  foramen  lacerum  in  the  base  of  the  skull. 


[Fig.  360. 


A view  of  the  distribution  of  the  glosso-pharyngeal,  pnenmogastric,  and  spinal  aecessory  nerves, 
or  the  eighth  pair.  1.  The  inferior  maxillary  nerve.  2.  The  gustatory  nerve.  3.  The  chorda 
tympuni.  4.  The  auricular  nerve.  5.  Its  communication  with  the  portiodura.  6.  The  Incia! 
nerve  coming  out  of  the  stylo-mastoid  foramen.  7.  The  glosso-pharyngeal  nerve.  8.  Branches 
to  the  stylo-pharyngeus  muscle.  9.  The  pharyngeal  branch  of  the  pneumogastric  nerve  descending 
to  form  the  pharyngeal  plexus.  JO.  Branches  of  the  glosso  pharyngeal  to  the  pharyngeal  plexus. 
11.  7’he  pneumogastric  nerve.  12.  The  pharyngeal  plexus.  13.  'I'he  .superior  laryngeal  branch. 
14.  Branches  to  the  pharyngeal  plexus.  1.5,  15.  Communication  of  the  superior  and  inferior 
laryngeal  nerves.  16.  Cardiac  branches.  17.  Cardiac  branches  from  the  right  pneumogastric 
nerve.  18.  The  left  cardiac  ganglion  and  plexus.  19.  The  recurrent  or  inferior  laryngeal 
nerve.  20.  Branches  sent  from  the  curve  of  the  recurrent  nerve  to  the  pulmonary  plexus.  21. 
Tlie  anterior  pulmonary  plexus.  22,  22.  The  oesophageal  plexus. — Quain.] 


PNEUMOGASTRIC  NERVE— ITS  GANGLIA. 


287 


' In  passing  through  the  opening  at  the  base  of  the  skull  the  pneumo- 
gastric  nerve  is  contained  in  the  same  sheath  of  dura  mater,  and  sur- 
rounded by  the  same  tube  of  arachnoid  membrane  as  the  spinal 
accessory  nerve;  but  it  is  separated  from  the  end  of  the  lateral  sinus 
by  a process  of  fibrous  membrane,  or  of  bone,  and  from  the  glosso- 
pharyngeal nerve  by  a process  of  membrane.  In  the  foramen  the  fila- 
ments of  the  nerve  become  aggregated  together;  and  it  here  presents 
a ganglionic  enlargement,  distinguished  as  the  ganglion  of  the  root  of 
the  pneumogastric. 

After  its  passage  through  the  foramen,  the  vagus  nerve  is  joined  by 
the  accessory  part  of  the  spinal  accessory  nerve,  and  a second  gan- 
glion is  formed  upon  it  (the  ganglion  of  the  trunk  of  the  nerve). 
Several  communications  are 


at  the  same  time  established  Fig.  361. 

with  the  surrounding  nerves. 

In  its  course  along  the  neck 
the  nerve  has  a straight  direc- 
tion, and  a fixed  position  with 
respect  to  the  cervical  ves- 
sels; for,  enclosed  in  the 
sheath  of  those  vessels,  it  is 
between  the  internal  carotid 
artery  and  the  internal  jugular 
vein  as  far  as  the  thyroid  car- 
tilage, and  afterwards  between 
the  same  vein  and  the  com- 
mon carotid  artery.  When 
entering  the  thorax,  the  nerve 
of  the  right  side  crosses  over 
the  subclavian  artery  at  right 
angles,  and  gives  the  recur- 
rent branch  to  the  larynx 

round  that  vessel;  but  on  the  Diagram  from  Bendz  of  the  ganglia  and  communi- 
left  side  it  is  parallel  with  the  pa'jonsof  the  divisions  of  the  eighth  pair,  A.  Cere- 
^ 1 bellum.  B.  Medulla  oblongata,  c.  Spinal  cord.  1 

and  ttie  Root  of  glosso-pharyngeal  nerve.  2.  Roots  of  vagus 
branch  Roots  of  spinal  accessory.  4.  Jugular  ganglion 
• ■ tu  u . Petrous  ganglion.  6.  Tympanic  branch.  7.  Gan 

at  ISeS  in  tne  cnest  opposite  glion  of  the  root  of  the  vagus.  8.  Auricular  branch 
the  arch  of  the  aorta.  Ganglion  of  the  trunk  of  vagus.  10.  Branch  from 

rpi  T the  last  to  the  petrous  ganglion.  11.  Inner  portion  of 

LhQ  UppP.r  ganglion  or  gan-  spinal  accessory.  12.  Outer  portion  of  the  same.  13. 
glion  of  the  root  of  the  pneu-  Pharyngeal  branch  of  vagus.  14.  Upper  laryngeal 
ji.  / ^ branch.  15.  Branches  to  the  sympathetic.  16.  Eas- 

mogastriC  nerve  (gang,  supe-  ciculus  of  spinal  accessory  prolonged  with  vagus, 
rius  V.  radicis  nervi  vagi)  fig. 

381,^,  is  situate  in  the  foramen  lacerum.  It  is  of  a grayish  colour, 
and  resembles  the  ganglion  on  the  posterior  root  of  a spinal  nerve. 
This. body  is  nearly  circular,  and  about  twm  lines  in  diameter;  it  has 
connecting  filaments  with  other  nerves, — viz.,  with  the  facial,  the 


subclavian  artery, 
recurrent  laryngeal 


* These  ganglia  have  been  described  particularly  by  Bendz. — See  " Tractatus  de  Con. 
nexu  inter  Nervum  Vagum  et  Accessorium  Willisii.”  Hen.  Car.  Bang  Bendz.  Haunite, 
1836. — Either  the  one  or  the  other  ganglion  had  been  previously  noticed  by  the  greater 
number  of  anatomists. 


288 


PNEUMOGASTRfC  NERVE— BRANCHES. 


petrous  ganglion  of  the  glosso-pharyngeal,  the  spinal  accessory,  and 
the  sympathetic. 

The  lower  ganglion,  (or  ganglion  of  the  trunk  of  the  pneumogastric 
nerve,*)  (ganglion  inferius  v.  trunci  nervi  vagi),  fig.  3til,®,  is  about 
half  an  inch  below  the  preceding.  Occupying  the  trunk  of  the  nerve 
outside  the  skull,  it  is  of  a cylindrical  form  and  reddish  colour,  and 
measures  about  ten  lines  in  length  and  two  in  breadth.  The  ganglion 
does  not  include  all  the  fibres  of  the  nerve;  the  fasciculus,  which  is 
sent  from  the  spinal  accessory  to  join  the  vagus,  is  the  part  not  in- 
volved in  the  ganglionic  substance.  It  communicates  with  the  spinal 
accessory,  the  hypoglossal,  the  spinal,  and  sympathetic  nerves. 

The  pneumogastric  nerves  in  the  thorax. — In  the  chest  the  pneumo- 
gastric nerves  supply  branches  to  the  lungs  and  heart,  and  are  then 
continued  through  the  cavity  along  the  oesophagus  to  the  stomach. 
As  there  is  some  difierence  between  the  nerves  of  opposite  sides  in 
this  part  of  their  course,  a separate  notice  of  each  becomes  necessary. 

The  ris;ht  pneumogastric  nerve  is  inclined  by  the  side  of  the  trachea 
to  the  back  of  the  root  of  the  lung,  where  it  spreads  out  in  a plexus 
(posterior  pulmonary).  From  the  lower  part  of  the  plexus  two  large 
cords,  the  continuation  of  the  nerve,  are  directed  to  the  oesophagus,  on 
which  they  subdivide,  and,  with  similar  branches  of  the  nerve  of  the 
left  side,  form  the  oesophageal  plexus.  Near  the  lower  part  of  the 
oesophagus  these  branches  are  collected  on  each  side  into  a single 
cord ; and  this  cord  on  the  left  side  is  placed  on  the  fore  part  of  liie 
oesophagus,  while  it  is  behind  that  tube  on  the  right  side.  In  this 
manner  the  trunks  of  both  nerves  are  continued  into  the  abdomen. 

The  nerve  of  the  left  side,  which  is  placed  nearer  to  the  fore  part 
of  the  thorax  than  its  fellow,  at  first  lies  between  the  left  carotid  and 
subclavian  arteries,  and  behind  the  left  innominate  vein.  Next  it 
crosses  over  the  arch  of  the  aorta  (round  which  turns  the  recurrent 
laryngeal  branch),  and  then  reaches  the  back  part  of  the  root  of  the 
lung.  Lastly,  the  nerve  rests  on  the  front  of  the  oesophagus,  as  before 
stated. 

In  the  Abdomen  : — Both  pneumogastric  nerves  enter  the  abdomen 
with  the  oesophagus,  and  are  distributed  to  the  surfaces  of  the  sto- 
mach, the  left  nerve  spreading  on  the  fore  part,  and  the  right  on  the 
posterior  aspect  of  that  organ.  Offsets  are  also  given  to  plexuses  of 
the  sympathetic  : from  the  right  nerve  one  to  the  coeliac  plexus,  and 
from  the  left  another  to  the  left  hepatic  plexus. 

branches  of  the  pneumogastric  nerve. 

Some  of  the  branches  serve  to  connect  the  pneumogastric  with 
other  nerves,  and  other  branches  are  distributed  to  the  muscular  sub- 
stance or  the  mucous  lining  Of  the  organs  which  the  nerve  supplies. 
The  principal  connecting  branches  of  this  nerve  are  derived  from  the 
ganglia.  In  the  different  stages  of  its  course,  branches  are  supplied  to 

* This  ganglion  was  named  superior  laryngeal  by  Sir  Astley  Cooper,  from  the  supposi- 
tion that  it  was  the  special  ganglion  of  the  superior  laryngeal  nerve,  and  that  it  bestowed 
sensory  powers  on  that  nerve, — See  a paper  in  “ Guy's  Hospital  Reports,"  No.  5.  Oct. 
1837.  London. 


SUPERIOR  LARYNGEAL  BRANCH. 


289 


various  organs  as  follows  : — In  the  jugular  foramen,  a branch  is  given 
to  the  ear ; in  the  neck,  branches  are  successively  furnished  to  the 
pharynx,  the  larynx,  and  the  heart;  and  in  the  thorax,  additional 
branches  are  distributed  to  the  heart,  and  others  to  the  lungs  and  the 
oesophagus.  The  terminal  branches  in  the  abdomen  have  been  already 
indicated. 

CONNECTING  BRANCHES  AND  AURICULAR  BRANCH. 

1.  Connexions  between  the  upper  ganglion  of  the  vagus  nerve  and  the  spinal  accessory, 
glosso-pharyngeal,  and  sympathetic  nerves. — The  connexion  with  the  spinal  acces- 
sory is  effected  by  one  or  two  filaments.  The  filament  to  the  petrous  ganglion  of 
the  glosso-pharyngeaT  is  directed  transversely;  it  is  not  always  present.  The 
communication  with  the  sympathetic  is  established  by  means  of  the  ascending 
offset  of  the  upper  cervical  ganglion. 

2.  The  auricular  branch  connects  the  pneumogastric  with  the  facial  nerve  in  the 
petrous  substance  of  the  temporal  bone,  and  is  then  continued  to  the  pinna  of  the 
ear.  Arising  from  the  ganglion  of  the  root,  this  branch  is  joined  by  a filament 
from  the  glosso-pharyngeal  nerve ; it  then  turns  backwards  along  the  outer  bound- 
ary of  the  jugular  foramen  to  an  opening  near  the  styloid  process.  Next,  it  tra- 
verses the  substance  of  the  temporal  bone,  crossing  the  aqueduct  of  Fallopius, 
about  two  lines  from  its  lower  end,  and,  reaching  the  surface  between  the  mas- 
toid process  and  the  external  auditory  meatus,  is  distributed  to  the  integument  of 
the  back  of  the  ear.  In  the  bone  the  auricular  branch  is  connected  with  the 
facial  nerve  (which  it  crosses),  and  on  the  surface  it  joins  with  an  offset  of  the 
posterior  auricular  branch  of  the  same  nerve. 

3.  Connexions  of  the  second  ganglion  of  the  vagus  with  the  spinal  accessory,  hypo- 
glossal, sympathetic,  and  spinal  nerves.- — Independently  of  its  connexion  with  the 
inner  division  of  the  spinal  accessory,  which  becomes  part  of  the  pneumogastric 
nerve,  this  ganglion  is  connected  by  filaments  with  the  trunk  of  the  hypoglossal, 
with  the  upper  cervical  ganglion  of  the  sympathetic,  and  with  the  loop  formed 
between  the  first  two  cervical  nerves. 

BRANCHES  FOR  THE  PHARYNX,  LARYNX,  AND  HEART. 

1.  Pharyngeal  Branch. 

The  pharyngeal  branch,  fig.  361,  arises  from  the  upper  part  of 
the  ganglion  of  the  trunk  of  the  nerve.  In  its  progress  inwards  to  the 
pharynx  this  nerve  crosses,  in  one  case  over,  in  another  under  the  in- 
ternal carotid  artery ; and  it  divides  into  branches,  which,  conjointly 
with  others  derived  from  the  glosso-pharyngeal,  the  superior  laryn- 
geal, and  the  sympathetic  nerves,  form  a plexus  {■pharyngeal)  behind 
the  middle  constrictor  of  the  pharynx.  From  the  plexus,  branches  are 
given  to  the  muscular  structure  and  the  mucous  membrane  of  the  pha- 
rynx. As  the  pharyngeal  nerve  crosses  the  carotid  artery,  some  fila- 
ments join  those  which  the  glosso-pharyngeal  distributes  on  the  same 
vessel. — There  is  sometimes  a second  pharyngeal  branch. 

2.  Superior  Laryngeal  Branch. 

This  nerve,  fig.  361,  springs  from  the  middle  of  the  ganglion  of 
the  trunk  of  the  pneumogastric  nerve.  It  is  directed  inwards  to  the 
larynx  beneath  the  internal  carotid  artery,  and  divides  beneath  that 
vessel  into  two  branches,  distinguished  as  external  and  internal  laryn- 
geal, both  ramifying  in  the  structures  of  the  larynx. 

The  external  laryngeal  branch,  the  smaller  of  the  two  divisions,  at 
the  side  of  the  pharynx  gives  backwards  filaments  to  the  pharyngeal 

VOL.  II.  25 


290 


CARDIAC  BRANCHES. 


plexus  and  to  the  lower  constrictor  muscle ; and  it  is  finally  prolonged 
beneath  the  muscles  on  the  side  of  the  larynx  to  the  crico-lhyroid 
muscle*  and  the  thyroid  body,  in  which  it  ends.  In  the  neck  this 
branch  joins  the  upper  cardiac  nerve  of  the  sympathetic. 

The  internal  division  of  the  laryngeal  nerve  is  continued  to  the  in- 
terval between  the  hyoid  bone  and  the  thyroid  cartilage,  where  it  per- 
forates the  thyro-hyoid  membrane  with  the  laryngeal  branch  of  the 
thyroid  artery,  and  sends  an  otl’set  to  join  the  recurrent  branch,  after 
distributing  several  filaments  to  the  mucous  inembrane.f 

a.  Branches  to  the  mucous  membrane. — Some  twigs  of  the  internal  laryngeal  nerve 
enter  the  mucous  membrane  of  the  pharynx,  and  communicate  with  filaments  to 
the  same  part  from  the  recurrent  nerve ; others  are  directed  upwards  in  the  ary- 
tseno-epiglottidean  fold  of  mucous  membrane  to  the  base  of  the  tongue,  the  epi- 
glottis, and  epiglottidean  gland ; and  others  are  reflected  downwards  in  the  lining 
membrane  of  the  larynx,  extending  to  the  chorda  vocalis : these  last  are  placed  o r 
the  inner  side  of  the  laryngeal  pouch. 

h.  The  communicating  branch  to  the  recurrent  laryngeal  nerve  is  very  slender, 
and  lies  beneath  the  lateral  part  of  the  thyroid  cartilage,  under  which  the  junction 
between  the  two  nerves  takes  place. 

3.  Recurrent  Laryngeal  Branch. 

The  recurrent  or  inferior  laryngeal  branch  of  the  vagus  nerve,  fig. 
360,*®,  as  the  name  expresses,  has  a reflex  course  to  the  larynx,  but 
the  point  of  departure  from  the  vagus  nerve  and  the  connexions  are 
not  the  same  on  both  sides  of  the  body. 

The  nerve  on  the  right  side  arises  at  the  top  of  the  thorax,  winds 
round  the  subclavian  artery,  and  crosses  beneath  the  common  carotid 
and  lower  thyroid  artery  in  its  course  to  the  trachea.  On  the  left  side 
the  recurrent  nerve  is  bent  round  the  arch  of  the  aorta  at  the  point 
where  the  obliterated  ductus  arteriosus  is  connected  with  the  arch, 
and  is  thence  inclined  upwards  to  the  trachea. 

Each  nerve  in  its  course  to  the  larynx  is  placed  between  the  trachea 
and  oesophagus,  supplying  branches  to  both  tubes  ; and,  whilst  making 
the  turn  round  its  vessel,  each  gives  nerves  to  the  deep  cardiac  plexus. 
At  the  low’er  part  of  the  cricoid  cartilage  the  recurrent  nerve  distri- 
butes muscular  branches,  a few  ofl’sets  to  the  mucous  membrane,  arid 
a single  communicating  filament. 

a.  The  branches  to  the  mucous  membrane  of  the  pharynx,  few  in  number,  unite  in 
their  ramifications  with  branches  from  the  upper  laryngeal  nerve. 

b.  The  muscular  branches  supply  all  the  proper  muscles  of  the  larynx,  except  the 
crico-thyroid  muscle,  which  is  supplied  from  the  upper  laryngeal  nerve. 

c.  The  communicating  filament  joins  the  long  branch  of  the  upper  laryngeal  nerre 
beneath  the  side  of  the  thyroid  cartilage. 

4.  Cardiac  Branches. 

The  cervical  cardiac  branches  arise  both  at  the  upper  and  the  lower  part  of  the 
neck.  The  upper  branches  are  small,  and  join  the  cardiac  nerves  of  the  sympatlie- 

* Bendz  describes  branches  to  the  muscles  fixed  to  the  oblique  line  on  the  thyroid  car- 
tilage— viz.,  to  the  constrictor,  sterno-thyroid,  and  thyro  hyoid  muscles. 

+ A branch  to  the  arytmnoid  muscle  is  sometimes  described.  It  is  difficult  to  say 
whether  the  nerve  supplies  that  muscle,  but  it  appears  to  do  so.  A branch  enters  the 
muscle,  some  filaments  seem  to  end  in  it,  and  others  proceed  through  it  to  the  mucous 
membrane. 


GASTRIC  BRANCHES. 


291 


tic.  The  lower,  a single  branch,  arises  as  the  pneumogastric  nerve  is  about  to 
enter  the  chest.  On  the  right  side  this  branch  lies  by  the  side  of  the  innominate 
artery,  and  joins  one  of  the  cardiac  nerves  destined  for  the  deep  cardiac  plexus  ] 
it  gives  some  filaments  to  the  coats  of  the  aorta.  The  branch  of  the  left  pneumo- 
gastric crosses  the  arch  of  the  'aorta,  and  ends  in  the  superficial  cardiac  plexus. 

BRANCHES  IN  THE  CHEST  AND  ABDOMEN. 

1.  Cardiac  Branches. 

The  thoracic  cardiac  branches  of  the  right  side  leave  the  trunk  of  the  pneumo- 
gastric, as  this  nerve  lies  by  the  side  of  the  trachea ; they  pass  inwards  on  the 
air-tube,  and  end  in  the  deep  cardiac  plexus.  The  corresponding  branches  of  the 
left  side  come  from  the  left  recurrent  larjmgeal  nerve. 

2.  Pulmonary  Br9,nches. 

Two  sets  of  pulmonary  branches  are  distributed  from  the  pneumogastric  nerve 
to  the  lung ; and  they  reach  the  root  of  the  lung,  one  on  its  fore  part,  the  other  on 
its  posterior  aspect.  The  anterior  pulmonary  nerves,  two  or  three  in  number,  are 
of  small  size.  They  join  with  filaments  of  the  sympathetic  continued  on  the  pul- 
monary artery,  and  with  these  nerves  constitute  the  anterior  pulmonary  plexus. 
Behind  the  root  of  the  lung  the  pneumogastric  becomes  flattened,  and  gives  seve- 
ral branches  (of  much  larger  size  than  the  anterior  branches),  which,  with  fila- 
ments derived  from  the  third  and  fourth  thoracic  ganglia  of  the  sympathetic, 
form  the  posterior  pulmonary  plexus.  Offsets  from  the  last-named  plexus  extend 
along  the  ramifications  of  the  air-tube  through  the  substance  of  the  lung. 

3.  (Esophageal  Branches. 

The  oesophagus  within  the  thorax  receives  branches  from  the  pneumogastric 
nerves,  both  above  and  below  the  pulmonary  branches.  The  latter  are  the 
larger,  and  are  derived  from  the  oesophageal  plexus  (plexus  gulae).  This  plexus  is 
formed  by  connecting  cords  between  the  nerves  of  the  right  and  left  sides,  while 
they  lie  in  contact  with  the  oesophagus. 

4.  Gastric  Branches. 

The  branches  distributed  to  the  stomach  {gastric  nerves)  are  the  terminal 
branches  of  both  pneumogastric  nerves.  The  nerve  of  the  left  side,  on  arriving, 
guided  by  the  oesophagus,  opposite  the  cardiac  orifice  of  the  stomach,  divides 
into  many  branches : some  of  these  extend  over  the  fore  part  of  the  stomach ; 
others  lie  along  its  small  curvature,  and  unite  with  branches  of  the  right  nerve 
and  the  sympathetic ; and  filaments  are  continued  between  the  layers  of  the 
small  omentum  to  the  left  hepatic  plexus.  The  right  pneumogastric  nerve  dis- 
tributes branches  to  the  posterior  surface  and  the  cardiac  end  of  the  stomach ; 
and  a part  of  this  nerve  is  continued  from  the  stomach  to  the  left  side  of  the 
cceliac  plexus  of  the  sympathetic. 

Summary. — The  pneumogastric  nerves  supply  branches  to  the  upper 
part  of  the  alimenlary  canal,  viz.,  the  pharynx,  oesophagus,  and  sto- 
mach ; and  to  the  respiratory  organs,  namely,  the  larynx,  trachea,  and 
lungs.  These  nerves  give  branches  likewise  to  the  heart  and  great 
vessels  by  means  of  their  communication  with  the  cardiac  plexus. 
Each  pneumogastric  nerve  is  connected  with  the  following  cranial 
nerves — the  spinal  accessory,  glosso-pharyngeal,  facial,  and  hypo- 
glossal; also,  with  some  spinal  nerves;  and  with  the  sympathetic  in 
the  neck,  the  thorax,  and  abdomen. 


292 


NINTH  PAIR  OF  CRANIAL  NERVFS. 


C.  SPINAL  ACCESSORY  NERVE. 

The  spinal  nerve  accessory  to  ihe  vagus  nerve,  or,  as  it  is  shortly 
named,  the  spinal  accessory  nerve  (nervus  spinalis  ad  par  vaguni 
accessorius,  eleventh  cranial  nerve  of  Scemmerring),  fig.  361,  gives  a 
fasciculus  to  join  the  trunk  of  the  pneumogastric,  and  supplies  branches 
to  the  slerno-mastoid  and  trapezius  muscles. 

The  place  of  origin  of  this  nerve  from  the  spinal  cord  and  its  course 
in  the  spinal  canal  to  the  cranium,  where  it  is  associated  wdth  the  other 
parts  of  the  eighth  pair,  have  been  already  described,  ante,  p.  247. 
From  the  side  of  the  medulla  oblongata  it  is  directed  outwards  to  the 
foramen  lacerum  posterius,  and  is  transmitted  through  that  opening  in 
the  same  sheath  of  dura  mater  as  the  pneumogastric  nerve.  In  the 
foramen  this  nerve  is  connected  with  the  ganglion  of  the  root  of  the 
pneumogastric  by  one  or  more  short  filaments.  After  escaping  from 
the  cranium,  it  is  concealed  by  the  internal  jugular  vein,  and  immedi- 
ately divides  into  two  parts,  one  of  which  (the  internal  part)  joins  the 
vagus  nerve,  the  other  (the  external  one)  supplies  the  sterno-mastoid 
and  trapezius  muscles. 

The  internal  or  accessory  division,  the  smaller  of  the  two,  gets  at 
once  into  contact  with  the  vagus  nerve,  close  to  the  base  of  the  skull, 
and  blends  with  that  nerve  beyond  its  second  ganglion.* 

The  external  division  of  the  spinal  accessory  nerve  is  directed  back- 
wards, and  after  crossing  the  internal  jugular  vein,  in  one  case  over, 
in  another  under  the  vein,  perforates  the  sterno-mastoid  muscle,  at  the 
same  time  supplying  it  with  branches,  and  communicating  in  its  sub- 
stance with  branches  of  the  cervical  plexus.  Crossing,  in  the  next 
place,  the  neck  behind  the  sterno-mastoid,  the  nerve  passes  beneath 
the  trapezius  muscle.  Here  it  forms  a kind  of  plexus  with  branches 
of  the  third  and  fourth  cervical  nerves,  and  distributes  offsets  to  the 
trapezius,  which  extend  nearly  to  the  lower  edge  of  the  muscle.  Be- 
sides the  communications  between  the  spinal  accessory  and  the  spinal 
nerves  already  mentioned,  another  communication  is  formed  with 
branches  of  the  cervical  nerves  in  the  interval  between  the  two  mus- 
cles to  which  the  nerve  is  distributed. 

NINTH  PAIR  OF  CRANIAL  NERVES. 

The  hypoglossal,  or  ninth  cranial  nerve  (nerv.  hypoglossus,  par 
nonum, — Willis,  twelfth  cranial  nerve, — Scemmerring),  fig.  362,  is  the 
motor  nerve  of  the  tongue.  ^ 

The  filaments  by  which  this  nerve  arises  from  the  medulla  oblon- 
gata are  collected  into  two  bundles,  which  converge  to  the  anterior 
condyloid  foramen  of  the  occipital  bone.  Each  bundle  of  filaments 
perforates  the  dura  mater  separately  opposite  the  foramen,  and  the  two 
are  joined  after  they  have  passed  through  it. 

* It  is  stated  by  Bendz  that  a filament  is  given  from  the  spinal  accessory  to  the  pha- 
ryngeal  nerve  above  tlie  place  of  junction  with  the  vagus,  and  that  fibrils  of  the  same  nerve 
have  been  traced  into  each  of  the  muscular  offsets  of  the  pneumogastric  nerve. 


MUSCULAR  BRANCHES. 


293 


After  leaving  the  cranium, 
this  nerve  descends  almost  ver- 
tically to  the  lower  border  of 
the  digastric  muscle,  and, 
changing  its  course,  is  thence 
directed  forwards  above  the 
hyoid  bone,  and  between  the 
muscles  in  this  situation  to  the 
under  part  of  the  tongue. 

As  it  descends  from  the  base 
of  the  skull,  the  hypoglossal 
nerve  lies  at  first  very  deeply ' 
with  the  vagus  nerve,  to  which 
it  is  connected  ; but  it  gradu- 
ally approaches  nearer  to  the 
surface,  passing  between  the 


Fig.  362. 


Diagram  of  the  trunk  of  the  hypoglossal  nerve.  1. 


internal  carotid  artery  and  Trunk  of  the  nerve.  3.  Descending  cervical  branch. 

vein.  VV  uere  it  serves  to  form  the  arch  with  the  descendens  noni. 

curves  forward  towards  the 

tongue,  the  nerve  turns  round  the  occipital  artery,  and  then  crosses 
the  external  carotid  below  the  tendon  of  the  digastric  muscle.  It  next 
sinks  under  the  mylo-hyoid  muscle,  lying  between  it  and  the  hyo- 
glossus,  and  at  the  inner  border  of  the  latter  is  connected  with  the 
gustatory  nerve.  Finally,  it  is  continued  in  the  fibres  of  the  genio-hyo- 
glossus  muscle  beneath  the  tongue  to  its  point,  and  distributes  branches 
upwards  to  the  muscular  substance. 

The  principal  branches  of  this  nerve  are  distributed  to  muscles  on 
the  fore  part  of  the  neck  and  to  the  tongue ; a few  serve  to  connect  it 
with  some  of  the  neighbouring  nerves.  The  several  branches  are  dis- 
posed in  the  following  manner: — 


CONNEXION  WITH  OTHER  NERVES. 

1.  Connexion  with  the  pneumogastric. — Close  to  the  skull  the  hypoglossal  nerve 
is  connected  with  the  second  ganglion  of  the  pneumogastric  by  separate  filaments, 
or  both  nerves  are  united  so  as  to  form  but  one  mass. 

2.  With  the  sympathetic  and  first  two  spinal  nerves. — Opposite  the  first  cervical 
vertebra  the  nerve  communicates  with  the  upper  cervical  ganglion  of  the  sym- 
pathetic, and  with  the  loop  connecting  the  first  two  spinal  nerves  in  front  of  the 
atlas. 


MUSCULAR  BRANCHES. 

1.  Descending  Branch  of  the  Ninth  Nerve. 

This  branch  (r.  descendens  noni),  fig.  362,  leaves  the  ninth  nerve  where  this 
turns  round  the  occipital  artery,  or,  it  may  be,  higher  up.*  It  is  directed  across 
the  sheath  of  the  carotid  vessels,  from  the  outer  to  the  inner  side,  and  joins  about 
the  middle  of  the  neck  in  a loop  with  one  or  two  branches  of  the  cervical  plexus. 
The  convexity  of  this  loop  is  turned  downwards ; and  the  connexion  between  the 
nerves  is  effected  by  means  of  two  or  more  interlacing  filaments,  which  inclose 
an  irregularly-shaped  space.  From  this  interlacement  of  the  nerves,  filaments 
are  continued  backwards  to  the  posterior  belly  of  the  omo-hyoid,  whilst  others 
are  directed  forwards  to  the  anterior  belly  of  the  same  muscle,  and  to  the  sterno- 

* This  nerve  may  be  derived  altogether  from  the  pneumogastric,  or  from  both  the 
pneumogastric  and  hypoglossal  nerves. 


25* 


294 


THE  SPINAL  NERVES. 


hyoid  and  sterno-thyroid  muscles.  It  occasionally  happens  that  a filament  is 
continued  to  the  chest,  where  it  joins  the  cardiac  and  phrenic  nerves. 

It  is  not  uncommon  to  find  the  descending  branch  of  the  ninth  nerve  in  the 
sheath  with  the  large  cervical  vessels,  and  in  such  cases  it  may  be  placed  either 
over  or  under  the  vein. 

2.  Branches  to  the  Tongue  and  Neighbouring  Muscles. 

Branches  are  distributed  to  the  following  muscles,  viz.,  the  thyro-hyoid,  stylo- 
glossus, hyo-glossus,  genio-hyoid,  and  genio-hyo-glossus.  These  branches  sepa- 
rate from  the  nerve  where  it  is  contiguous  to  the  several  muscles;  that  for  the 
thyro-hyoid  muscle  near  the  end  of  the  hyoid  bone  before  the  perve  passes 
beneath  the  mylo-hyoid  muscle.  Lastly,  the  hypoglossal  nerve,  when  arrived 
close  to  the  middle  of  the  tongue  with  the  ranine  artery,  gives  off  several  long 
slender  branches,  which  pass  upwards  into  the  substance  of  the  organ.  Some  of 
the  branches  join  with  offsets  from  the  gustatory  nerve. 

Summary. — The  hypoglossal  nerve  supplies  all  the  muscles  con- 
nected with  the  os  hyoides,  including  those  of  the  tongue,  with  the 
exception  of  the  digastric,  the  mylo-hyoid  and  the  middle  constrictor 
of  the  pharynx.  The  sterno-thyroid  muscle  likewise  receives  its  nerve 
from  the  same  source. 

It  is  connected  with  the  following  nerves,  viz.,  pneumogastric,  gus- 
tatory, some  spinal  nerves,  and  the  sympathetic. 


THE  SPINAL  NERVES. 

The  spinal  nerves  are  characterized  by  their  origin  from  the  spinal 
cord  and  their  direct  transmission  outward  from  ihe  spinal  canal  in 
the  intervals  between  the  vertebrce.  Taken  together,  these  nerves 
consist  of  thirty-one  pairs;  and,  like  the  vertebrae  between  which  they 
issue  from  the  spinal  canal,  they  are  arranged  into  groups  named 
cervical,  dorsal,  lumbar,  sacral,  and  coccygeal.  In  these  groups  the 
nerves  are  equal  in  number  to  the  vertebrae  composing  the  division  of 
the  column  with  which  they  are  associated,  but  with  these  exceptions, 
namely,  that  eight  cervical  nerves  are  recognised,  and  there  is  usually 
but  a single  coccygeal  nerve.* 

Each  spinal  nerve  springs  from  the  spinal  cord  by  two  roots  which 
approach  one  another,  and,  with  few  exceptions,  join  in  the  cor- 
responding intervertebral  foramen  into  a single  cord;  and  each  cord 
so  constructed  separates  immediately  into  two  divisions,  one  of  which 
is  destined  for  parts  in  front  of  the  spine,  the  other  for  parts  behind  it. 

The  nerves  which  do  not  emerge  from  the  spinal  canal  through 
intervertebral  foramina,  and  on  account  of  which  a reservation  has 
been  made  above,  are  the  first  and  second  cervical,  the  last  sacral, 
and  the  coccygeal  nerve.  The  two  cervical  nerves  issue  from  the 

* Among  seven  cases  which  appear  to  have  been  examined  with  great  care,  Professor 
Schlemm  (“Observat.  NeurologicEe,”  Berolini,  1834)  found  two  coccygeal  nerves  on  each 
side  in  one  instance,  and  on  one  side  in  another  case,  In  all  the  rest  there  was  but  a 
single  coccygeal  nerve  on  each  side.  The  occurrence  of  two  coccygeal  nerves  is,  there- 
fore, an  exception  to  the  usual  arrangement. 


ROOTS  OF  SPINAL  NERVES. 


295 


canal  over  the  laminae  of  the  vertebrae, — the  first  over  the  atlas,  the 
second  over  the  axis;  and  the  other  two  take  their  course  outwards 
through  the  end  of  the  sacral  canal. 

The  connexions  of  the  roots  of  the  spinal  nerves  with  the  spinal 
cord,  and  the  manner  in  which  they  are  disposed  with  reference  to  its 
investing  membranes,  have  been  treated  of  already  {ante,  pp.  192,  247,‘ 
250).  It  remains  to  notice  the  characters  by  which  each  of  the  two 
roots  is  distinguished,  and  the  peculiarities  they  present  iii  different 
sets  of  nerves. 

THE  ROOTS  OF  THE  SPINAL  NERVES. 

The  posterior  roots  of  the  nerves  are  distinguished  from  the  anterior' 
roots  by  their  greater  size,  as  well  as  by  the  greater  thickness  of  the 
fibrils  of  which  they  are  composed.  But  these  roots  are  chiefly 
characterized  by  the  presence  of  ganglia.  At  some  distance  from  the 
spinal  cord  the  fibrils  of  the  posterior  root  of  an  individual  nerve  are 
aggregated  into  two  bundles ; and  these  swell,  so  to  say,  into  the  gan- 
glionic enlargement. 

Ganglia  of  the  spinal  nerves. — The  spinal  nerves  are  each  furnished 
with  a ganglion;  but  the  first  cervical  or  suboccipital  nerve  is  in  some 
cases  without  one.  The  ganglia  are  proportioned  in  size  to  the  nerves 
on  which  they  are  formed.  They  are  oval  in  shape,  and  many  are 
partially  divided  or  notched  at  the  inner  side,  the  two  parts  involving 
the  bundles  into  which  the  fibrils  of  the  posterior  root  have  just  been 
said  to  be  arranged. 

The  ganglia  are  placed  in  the  intervertebral  foramina,  immediately 
beyond  the  point  at  which  the  roots  perforate  the  dura  mater  lining 
the  spinal  canal.  From  this  statement  those  on  a few  nerves  are  to 
be  excepted.  Thus,  the  first  and  second  cervical  nerves,  which  leave 
the  spinal  canal  over  the  laminse  of  the  vertebrae,  have  their  ganglia 
opposite  that  part.  The  ganglion  of  the  coccygeal  nerve  is  placed 
within  the  canal  in  the  sac  of  dura  mater,  and  at  a variable  distance 
from  the  origin  of  the  nerve ; and  the  ganglion  of  the  last  sacral  nerve, 
in  some  cases,  occupies  a similar  position. 

The  anterior  roots  of  the  spinal  nerves  are,  as  will  be  inferred  from 
what  has  been  already  slated,  the  smaller  of  the  two,  and  are  devoid 
of  ganglionic  enlargement. 

The  roots  of  the  different  groups  of  spinal  nerves  vary  considerably 
in  size,  and  some  variation  is  likewise  observable  in  the  relative  thick- 
ness of  the  fibrils  of  which  they  are  composed. 

Size. — The  roots  of  the  upper  cervical  nerves  are  much  smaller 
than  those  of  the  lower  nerves,  the  first  being  much  the  smallest. 
The  posterior  roots  of  these  nerves  exceed  the  anterior  in  size  more 
than  in  the  other  classes  of  the  spinal  nerves,  and  they  are  likewise 
composed  of  fibrils  which  are  considerably  larger  than  those  of  the 
anterior  roots. 

The  roots  of  the  dorsal  nerves,  exception  being  made  of  the  fir.st, 
(which  resembles  the  lowest  cervical  nerves  and  is  associated  with 
them  in  its  distribution,)  are  of  small  size,  and  vary  but  slightly,  or  not 
at  all,  from  the  second  to  the  last.  The  fibrils  of  both  roots  are  thinly 


296 


ROOTS  OF  SPINAL  NERVES. 


strewed  over  the  cord,  and  are  slender,  those  of  the  posterior  exceed- 
ing in  thickness  those  of  the  anterior  root  in  only  a small  degree. 

The  roots  of  the  lower  lumbar,  and  of  the  upper  sacral  nerves,  are 
the  largest  of  all  the  spinal  nerves ; those  of  the  lowest  sacral  and  the 
coccygeal  nerve  are,  on  the  other  hand,  the  slenderest  of  all.  All 
these  nerves  are  crowded  together  on  the  lower  end  of  the  cord.  As 
regards  the  relative  size  of  the  roots  of  the  same  nerves,  the  anterior 
are  the  smaller,  but  the  disproportion  between  the  two  is  not  so  great 
as  in  the  cervical  nerves. 

Length  and  direction  of  the  nerves  in  the  spinal  caflal. — The  place 
at  which  the  roots  of  the  upper  cervical  nerves  are  connected  with  the 
spinal  cord  being  nearly  opposite  the  foramina  by  which  they  leave 
the  canal,  these  roots  are  in  consequence  very  short.  But  the  distance 
between  the  two  points  referred  to  is  gradually  augmented  from  nerve 
to  nerve  downwards,  so  that  the  place  of  origin  of  the  lower  cervical 
nerves  is  the  breadth  of  at  least  one  vertebra,  and  that  of  the  lower 
dorsal  nerves  about  the  breadth  of  two  vertebrae  above  the  foramina, 
by  which  they  respectively  emerge  from  the  canal.  Moreover,  as  the 
spinal  cord  extends  no  further  than  the  first  lumbar  vertebra,  the  length 
of  the  roots  of  the  lumbar,  sacral,  and  coccygeal  nerves  increases 
rapidly  from  nerve  to  nerve,  and  in  each  case  may  be  estimated  by 
the  distance  of  the  foramen  of  exit  from  that  point.  Owing  to  their 
length  and  the  appearance  they  present  in  connexion  with  the  spinal 
cord,  the  aggregate  of  the  roots  of  the  nerves  last  referred  to  have 
been  named  the  “ cauda  equina.”* 

The  direction  the  roots  take  within  the  canal  requires  brief  notice. 
The  first  cervical  nerve  is  directed  horizontally  outwards.  The  roots 
of  the  lower  cervical  and  the  dorsal  nerves  at  first  descend  over  the 
spinal  cord,  held  in  connexion  with  it  by  the  arachnoid,  till  they  are 
arrived  opposite  the  several  intervertebral  foramina,  where  they  are 
directed  horizontally  outwards.  The  nerves  of  the  cauda  equina  are 
vertical  in  direction. 

The  two  roots  of  each  of  the  spinal  nerves  unite  immediately  beyond 
the  ganglion  on  the  posterior  one,  and  the  trunk  thus  formed  separaies 
immediately,  as  already  mentioned,  into  two  divisions,  anterior  and 
posterior.  To  these  we  shall  now  turn  attention,  beginning  with  the 
latter. 

Certain  characters  common  to  the  posterior  divisions  of  all  the  spinal 
nerves  will  first  be  noticed.  Afterw'ards  the  arrangement  peculiar  to 
each  group  of  nerves  (cervical,  dorsal,  &c.),  will  be  separately  con- 
sidered. 

* This  designation  originated  with  a comparison  made  by  Laurentius,  who,  it  may  be 
added,  regarded  the  nervous  cords  which  occupy  the  lower  part  of  the  spinal  canal  as  a 
portion  of  the  spinal  cord.  His  words  are  these  : — 

“ Medulla  autem  6 caluarice  rotu’do  et  ampio  foramine  prodiens,  primum  amplissima  et 
crassissima,  sensim  attenuatur,  id  est,  medullarem  substantiam  amiltit,  non  corpoream 
molem  quam  eandem  ubique  servat;  tandem  cbm  ad  dorsi  fines  peruenit,  tota  in  funicuios 
et  filamenta  caudam  fere  equinam  referentia  absumitur.” — And.  Laurentius,  “ IJistor. 
Humani  Corporis,”  lib.  x.  cap.  xii.,  Parisiis,  1600. 


J 


POSTERIOR  DIVISIONS  OF  THE  CERVICAL  NERVES. 


297 


POSTERIOR  DIVISIONS  OF  THE  SPINAL  NERVES. 

The  posterior  divisions  of  the  spinal  nerves  are,  with  few  exceptions, 
smaller  than  those  given  to  the  fore  part  of  the  body.  Springing  fronn 
the  trunk  which  results  from  the  union  of  the  roots  of  the  nerves  in 
the  intervertebral  foramina,  they  turn  backwards,  and  soon  divide 
each  into  two  parts  or  branches,  distinguished  as  external  and  internal ; 
and  these  are  distributed  to  the  muscles  and  the  integument  behind  the 
spine.  Exceptions  to  this  general  statement  respecting  the  division  of 
the  nerves  will  be  found  in  the  arrangement  of  the  first  cervical  and 
the  lower  sacral  nerves  ; the  peculiarities  which  they  present  will  be 
shown  in  the  special  description  of  those  nerves. 

POSTERIOR  DIVISIONS  OF  THE  CERVICAL  NERVES. 

These  nerves,  except  the  first  two,  are  directed  backwards  beneath 
the  posterior  intertransverse  muscle,  and  divide  behind  that  muscle 
into  the  external  and  internal  branches. 

The  external  branches  give  only  muscular  offsets,  and  are  distributed 
to  the  slender  muscles  prolonged  to  the  neck  from  the  erector  spinae, 
namely,  the  cervicalis  descendens  and  the  transversalis  colli  with  the 
trachelo-mastoid.  That  of  the  second  nerve  is  the  largest  of  the  series 
of  the  external  branches,  and  is  often  united  to  the  corresponding  branch 
of  the  third  ; it  supplies  the  complexus  muscle,  which  covers  it,  and  ends 
in  the  splenius  and  trachelo-mastoid  muscles.  The  first  cervical  nerve 
has  no  offset,  similar  to  the  external  branch  of  each  of  the  other  cer- 
vical nerves. 

H\\e  internal  branches,  vihlch.  are  larger  than  those  above  described, 
are  differently  disposed  at  the  upper  and  the  lower  parts  of  the  neck. 
Excluding  those  of  the  first  and  second  nerves,  which  require  separate 
notice,  they  are  directed  inwards  to  the  spinous  processes  of  the  ver- 
tebra;; but  the  branches  derived  from  the  third,  fourth,  and  fifth  nerves 
take  that  course  over  the  semispinalis,  and  beneath  the  complexus 
muscle,  and  having  reached  the  spines  of  the  vertebrm,  are  continued 
outwards  to  the  integument;  while,  on  the  other  hand,  the  branches 
from  the  lowest  three  cervical  nerves  are  placed  beneath  the  semispi- 
nalis muscle,  and  end  in  the  muscular  structure  without  furnishing 
(except  occasionally  the  sixth),  any  offset  to  the  skin.  The  last  three 
nerves  are  the  smallest  of  the  series. 

The  muscles  supplied  by  the  internal  branches  just  described  are 
the  complexus,  semispinalis  colli,  the  interspinales,  and  the  multifidus 
spinas. 

The  cutaneous  branches,  referred  to  as  furnished  by  the  internal 
branches  of  some  of  the  cervical  nerves,  reach  the  surface  by  the  side 
of  the  spinous  processes,  after  passing  through  the  fibres  of  the  com- 
plexus  (or  at  the  inner  side  of  that  muscle),  and  through  the  splenius 
and  trapezius  muscles;  and  then  turning  transversely  outwards,  are 
distributed  in  the  integument  over  the  trapezius  muscle. 

The  first  three  cervical  nerves  deviate  more  or  less  from  the  ar- 
rangement now  described,  and  require  to  be  noticed  individually. 


298 


SECOND  AND  THIRD  CERVICAL  NERVES. 


PECULIARITIES  IN  THE  POSTERIOR  DIVISIONS  OF  CERTAIN  CERVICAL  NERVES. 

1.  Suboccipital  Nerve. 

The  posterior  division,  which  is  the  larger  of  the  two  divisions  of 
the  suboccipital  nerve,  emerges  over  the  arch  of  the  atlas,  between  it 
and  the  vertebral  artery,  to  the  space  bounded  by  the  larger  rectus  and 
the  two  oblique  muscles;  and  after  a very  short  course,  divides  into 
branches  for  the  surrounding  muscles.  One  branch  descends  to  the 
lower  oblique  muscle,  and  gives  a filament,  which  passes  through  the 
fibres  of  that  muscle,  or  over  it,  to  join  the  second  cervical  nerve;, 
another  ascends  over  the  larger  rectus  muscle,  supplying  it  and  the 
smaller  rectus;  a third  enters  the  upper  oblique  muscle;*"  and  a fourth 
sinks  into  the  complexus,  where  that  muscle  covers  the  nerve  and  its 
branches. 

A cutaneous  branch  is  occasionally  given  to  the  back  of  the  head 
from  the  suboccipital  nerve;  it  accompanies  the  occipital  artery,  and 
is  connected  beneath  the  integument  with  the  great  and  small  occipital 
nerves.f 

2.  Second  Cervical  Nerve. 

The  posterior  division  of  the  second  cervical  nerve  is  much  the 
largest  of  the  series.  When  the  nerve  has  passed  through  the  liga- 
ment between  the  arches  of  the  vertebrae,  it  lies  below  the  inferior 
oblique  muscle  (wbich  it  supplies  with  one  or  two  filaments),  and  re- 
ceives a communicating  branch  from  the  first  nerve.  The  nerve  then 
separates  into  its  external  and  internal  branches  ; the  former  of  which 
has  been  noticed  with  the  corresponding  branches  from  the  cervical 
nerves. 

The  internal  branch  of  this  nerve,  from  its  size  and  destination 
named  the  great  occipital  nerve,  is  directed  upwards  on  the  lower 
oblique  muscle,  and  is  transmitted  to  the  surface  through  the  corn- 
plexus  and  trapezius,  near  their  cranial  attachments.  As  soon  as  the 
nerve  is  free  from  the  muscles,  it  is  joined  by  an  offset  of  the  cutaneous 
part  of  the  third  cervical  nerve;  and  ascending  with  the  occipital 
artery,  it  divides  into  branches,  which  radiate  over  the  occipital  part 
of  the  occipito-frontalis  muscle,  some  appearing  to  enter  the  muscle, 
and  others  joining  the  smaller  occipital  nerve. 

An  auricular  branch  is  sometimes  supplied  to  the  back  of  the  ear 
by  the  great  occipital  nerve,  and  muscular  branches  are  furnished  to 
the  complexus.  Whilst  it  is  beneath  the  complexus,  the  nerve  in  some 
cases  is  joined  by  an  offset  from  the  third  cervical  nerve. 

3.  Third  Cervical  Nerve. 

The  posterior  division  of  the  third  cervical  nerve  differs  from  the 
nerves  below  it,  chiefly  in  this  respect — viz.,  that  in  addition  to  a cuta- 

* Asch  states  that  this  branch  supplies  the  rectus  capitis  lateralis  muscle.  “ De  Prime 
Pare  Nervorum  Mediillie  Spinalis,”  § .vxxiii.  in  Ludwig  “ Scriptores  Neurologici,"  vol.  i. 

t This  nerve  has  occasionally  been  found  in  the  dissecting.room  of  University  College, 
It  was  first  recognised  by  James  Harrison,  M.D.,  (Session  1839-40,)  and  subsequently 
traced  more  fully  by  Mr.  E.  Hearne. 


THE  DORSAL  NERVES.  . 299 

neous  branch  to  the  neck,  it  furnishes  another  to  the  skin  over  the  oc- 
ciput, which  is  hence  named  its  occipital  branch. 

This  occipital  branch  separates  from  the  cutaneous  cervical  branch 
beneath  the  trapezius,  perforates  that  muscle,  and  ramifies  in  the  inte- 
gument on  the  lower  part  of  the  occiput,  lying  at  the  inner  side  of  the 
great  occipital  nerve.  It  is  connected  with  that  nerve. 

Between  the  posterior  divisions  of  the  first  three  cervical  nerves  a 
connexion  is  in  some  cases  established  beneath  the  complexus  by 
means  of  communicating  branches;  and  this  communication  between 
the  nerves  M.  Cruveilhier  has  designated  as  “ the  posterior  cervical 
plexus.”  The  arrangement  referred  to  can,  however,  scarcely  be  said 
in  any  case  to  constitute  a plexus,  inasmuch  as  the  connecting  cords 
are  single,  and  do  not  furnish  offsets,  and,  moreover,  the  connexion 
between  the  nerves  is  often  altogether  wanting. 

POSTERIOR  DIVISIONS  OF  THE  DORSAL  NERVES. 

Like  the  posterior  divisions  of  the  other  spinal  nerves,  these  are 
smaller  than  the  anterior  divisions  (intercostal)  from  the  same  nerves, 
and  divide  between  the  transverse  processes  of  the  vertebra;  into  in- 
ternal and  external  branches. 

The  internal  branches  of  the  upper  six  nerves  appear  in  the  interval 
between  the  multifidus  spinas  and  the  semispinalis  dorsi : they  supply 
those  muscles,  and  become  cutaneous  by  the  side  of  the  spinous  pro- 
cesses of  the  vertebrae.  The  same  branches  of  the  lower  six  dorsal 
nerves  are  placed  between  the  multifidus  spinae  and  longissimus  dorsi, 
and  end  in  the  former  muscle  without  giving  branches  to  the  inte- 
gument. 

The  external  branches  increase  in  size  from  above  downwards,  and 
the  lower  five  or  six  give  cutaneous  offsets.  These  external  branches 
are  directed  through  or  beneath  the  longissimus  dorsi  to  the  cellular 
space  between  this  muscle  and  the  sacro-lumbalis ; and  they  supply 
both  those  muscles,  together  with  the  small  muscles  by  which  they  are 
continued  upwards  to  the  neck,  and  the  levatores  costarum. 

The  cutaneous  branches  of  the  dorsal  nerves  vary  in  their  position, 
according  as  they  are  derived  from  the  internal  or  the  external  branches 
above  described.  Those  from  the  internal  branches  of  the  upper  six 
nerves  perforate  the  rhomboid  and  trapezius  muscles  close  to  the  spines 
of  the  vertebrae,  and  are  directed  outwards  in  the  integument ; the 
branch  from  the  second  nerve  reaches  as  far  as  the  scapula.  Gangli- 
form  enlargements  will  often  be  found  on  these  nerves.  The  cutaneous 
nerves  given  from  the  external  branches  emanate  from  the  lower  five 
or  six  dorsal  nerves,  and  are  transmitted  to  the  integument  through 
the  lower  serratus  muscle  and  the  fleshy  part  of  the  latissimus  dorsi, 
in  a line  with  the  angle  of  the  ribs. 

It  will  be  observed,  that  where  cutaneous  nerves  are  supplied  by  the 
internal  branches,  there  are  none  from  the  external  branches  of  the 
same  nerves,*  and  vice  versa;  and  that  the  branches  which  give  cuta- 

* Valentin  states  that  there  are  cutaneous  nerves  from  all  the  external  and  internal 
branches  ; “ Soemmerring  V.  Bau,”  &c.  While  this  statement  is  dissented  from,  it  should 
be  remarked  that  the  cutaneous  nerves  are  not  always  limited  to  the  number  mentioned  in 
the  text. 


300 


SACRAL  NERVES— POSTERIOR  DIVISIONS. 


neous  offsets  are  larger  than  those  that  end  in  muscles  without  reach- 
ing the  skin. 

POSTERIOR  DIVISIONS  OF  THE  LUMBAR  NERVES. 

The  branches  given  backwards  from  the  lumbar  nerves  resemble 
those  of  the  lower  dorsal  nerves  in  their  position  between  the  trans- 
verse processes,  and  their  division  into  internal  and  external  branches 
between  the  multifidus  spin®  and  erector  spinse  muscles. 

The  external  branches  enter  the  erector  spince,  and  give  filaments 
to  the  intertransverse  muscles.  From  the  upper  three,  cutaneous 
nerves  are  supplied ; and  from  the  last,  a fasciculus  descends  to  the 
corresponding  branch  of  the  first  sacral  nerve. — The  cutaneous  nerves 
given  from  the  external  branches  of  the  first  three  lumbar  nerves,  pierce 
the  fleshy  part  of  the  sacro-lumbalis,  and  the  aponeurosis  of  the  latis- 
simus  dorsi ; they  cross  the  crest  of  the  ilium  near  the  edge  of  the  erec- 
tor spinas,  and  terminate  in  the  integument  of  the  gluteal  region.  One 
or  more  of  the  filaments  may  be  traced  as  far  as  the  great  trochanter 
of  the  femur. 

The  internal  branches  wind  backwards  in  grooves  close  to  the  ar- 
ticular processes  of  the  vertebrm,  and  sink  into  the  muliifidus  spinse 
muscle. 

POSTERIOR  DIVISIONS  OF  THE  SACRAL  NERVES. 

These  nerves  issue  from  the  sacrum  through  the  fora.mina  on  its 
posterior  aspect.  The  first  three  are  covered  at  their  exit  from  the 
bone  by  the  multifidus  spinae  muscle,  and  they  bifurcate  like  the  pos- 
terior divisions  of  the  other  spinal  nerves;  but  the  remaining  two, 
which  are  below  that  muscle,  have  a peculiar  arrangement,  and  re- 
quire separate  examination. 

The  internal  branch  of  the  first  three  sacral  nerves  are  small,  and 
are  lost  in  the  multifidus  spime  muscle. 

The  external  branches  of  the  same  nerves  are  united  with  one  an- 
other, and  with  the  last  lumbar  and  foqrth  sacral  nerves,  so  as  to  form 
a series  of  anastomotic  loops  on  the  upper  part  of  the  sacrum.  These 
branches  are  then  directed  outwards  to  the  cutaneous  or  posterior 
surface  of  the  great  sacro-sciatic  ligament,  where,  covered  by  the 
gluteus  maximus  muscle,  they  form  a second  series  of  loops,  and  end 
in  cutaneous  nerves.* 

The  cutaneous  nerves  derived  from  the  second  series  of  loops  last 
referred  to,  pierce  the  great  gluteus  muscle  in  the  direction  of  a line 
from  the  posterior  spine  of  the  ilium  to  the  tip  of  the  coccyx.  They 
are  commonly  three  in  number, — one  is  near  the  innominate  bone,  an- 
other opposite  the  extremity  of  the  sacrum,  and  the  third  about  midway 
between  the  other  two.  All  are  directed  outwards  over  the  great 
gluteal  muscle. 

The  last  two  sacral  nerves  placed,  as  already  stated,  below  the  tnul- 

• In  six  dissections  made  by  Mr.  Ellis,  the  arrangement  of  these  nerves  mentioned  in 
the  text  was  the  most  frequent.  The  variations  to  which  it  is  liable  are  these: — the  first 
nerve  may  not  take  part  in  the  second  series  of  loops,  and  the  fourth  may  be  associated  with 
them. 


FIRST  AND  SECOND  CERVICAL  NERVES. 


301 


tifidiis  spinae  muscle,  are  smaller  than  those  above  them,  and  are  not 
divided  into  branches  like  those  nerves.  They  are  connected  one  with 
the  other  by  a loop  on  the  back  of  the  sacrum,  and  the  lowest  is  joined 
in  a similar  manner  with  the  coccygeal  nerve:  one  or  two  small  fila- 
ments from  these  sacral  nerves  are  distributed  behind  the  coccyx. 

POSTERIOR  DIVISION  OF  THE  COCCYGEAL  NERVE. 

This  division  of  the  coccygeal  nerve  is  very  small,  and  separates 
from  the  anterior  division  of  the  nerve  in  the  sacral  canal.  It  is  joined 
by  a communicating  filament  from  the  last  sacral  nerve,  and  ends  in 
the  fibrous  structure  about  the  posterior  surface  of  the  coccyx. 

ANTERIOR  DIVISIONS  OF  THE  SPINAL  NERVES. 

The  anterior  divisions  of  the  spinal  nerves  are  distributed  to  the 
parts  of  the  body  situated  in  front  of  the  vertebral  column,  including 
the  limbs.  They  are,  for  the  most  part,  considerably  larger  than  the 
posterior  divisions  of  the  nerves,  and  the  greater  size  is  attributable  to 
the  greater  mass  of  muscular  and  other  structures  which  they  are 
destined  to  supply.  These  nerves  spring  from  the  trunk  resulting  from 
the  union  of  the  two  roots  of  the  spinal  nerves  in  the  intervertebral 
foramina,  and  are  thence  directed  forwards  to  their  destination.  The 
first  two  cervical  nerves  deviate  from  this  arrangement ; and  the  sacral 
and  coccygeal  nerves  have,  in  some  degree,  a peculiar  disposition. 
The  peculiarities  in  each  of  these  cases  will  be  noticed  in  the  special 
description  of  the  nerves. 

The  anterior  branch  of  each  spinal  nerve  is  connected  by  slender 
filaments  with  the  sympathetic.  Lastly,  the  cervical,  lumbar  and 
sacral  nerves  form  plexuses  of  various  forms ; but  the  dorsal  nerves 
remain  separate  one  from  the  other. 

ANTERIOR  DIVISIONS  OF  THE  FIRST  FOUR  CERVICAL  NERVES. 

The  four  upper  cervical  nerves  form  the  cervical  plexus  by  their 
anterior  divisions.  These  appear  at  the  side  of  the  neck,  between  the 
scalenus  medius  and  rectus  anticus  major  muscles;  and  each  divides 
into  two  parts,  one  of  which  communicates  with  the  nerve  above,  and 
the  other  with  the  nerve  below.  Each  of  these  nerves  is  connected 
by  a communicating  filament  with  the  first  cervical  ganglion,  or  with 
the  cord  connecting  that  ganglion  with  the  second.  Before  the  de- 
scription of  the  plexus  resulting  from  the  intercommunication  of  these 
nerves  is  entered  on,  some  peculiarities  in  the  disposition  of  the  first 
two  cervical  nerves  must  be  noticed. 

PECULIARITIES  IN  THE  FIRST  AND  SECOND  NERVES. 

1.  Suboccipital  Nerve. 

The  anterior  division  of  the  first  nerve  runs  forwards  in  a groove 
on  the  atlas,  and  bends  downwards  in  front  of  the  transverse  process 
of  that  vertebra  to  join  the  second  nerve.  In  this  course  forwards  it 
lies  beneath  the  vertebral  artery,  and  at  the  inner  side  of  the  rectus 

VOL.  II.  26 


302 


CERVICAL  PLEXUS— BRANCHES. 


lateralis  muscle,  to  which  it  gives  a branch.*  As  it  crosses  the  fora- 
men in  the  transverse  process  of  the  atlas,  the  nerve  is  joined  by  a 
filament  from  the  sympathetic;  and  from  the  arch  {hop  of  the  atlas)  it 
makes  in  front  of  that  process,  branches  are  supplied  to  the  two  ante- 
rior recti  muscles.  Short  filaments  connect  this  part  of  the  nerve  with 
the  pneumogastric,  the  hypoglossal,  and  the  sympathetic  nerves. 

2.  Second  Cervical  Nerve. 

The  anterior  division  of  the  second  cervical  nerve,  beginning  be- 
tween the  arches  of  the  first  two  vertebrce,  is  directed  forwards 
between  their  transverse  processes,  being  placed  outside  the  vertebral 
artery,  and  beneath  the  intertransverse  and  other  muscles  fixed  to 
those  processes.  In  front  of  the  intertransverse  muscles  the  nerve 
divides  into  an  ascending  part,  which  joins  the  first  cervical  nerve, 
and  a descending  part  to  the  third. 

CERVICAL  PLEXUS. 

The  cervical  plexus  is  formed  by  the  first  four  cervdcal  nerves,  and 
distributes  branches  to  some  of  the  muscles  of  the  neck,  and  to  a 
portion  of  the  integument  of  the  head  and  of  the  neck.  It  is  placed 
opposite  the  first  four  vertebrm,  beneath  the  sterno-mastoid  muscle,  and 
rests  against  the  middle  scalenus  muscle  and  the  elevator  of  the  angle 
of  the  scapula.  The  disposition  of  the  nerves  in  the  plexus  is  easily 
recognised.  Each  nerve,  except  the  first,  branches  into  an  ascending 
and  a descending  part;  and  these  are  united  in  anastomotic  loops  with 
the  contiguous  nerves.  From  the  union  of  the  second  and  third 
nerves,  superficial  branches  are  supplied  to  the  head  and  neck ; and 
from  the  junction  of  the  third  with  the  fourth,  arise  the  cutaneous 
nerves  of  the  shoulder  and  chest.  Muscular  and  communicating  off- 
sets spring  from  the  same  nerves. 

The  branches  of  the  plexus  will  be  separated  into  two  sets  or  classes 
— a superficial  and  deep  one:  the  former  consisting  of  those  which 
ramify  over  the  cervical  fascia,  supplying  the  integument  and  some 
also  the  platysma;  the  latter  comprising  branches  which  are  dis- 
tributed for  the  most  part  to  the  muscles.  Again,  each  of  these  sets 
admits  of  being  subdivided  into  two  series,  according  to  the  direction 
the  nerves  take.  Thus,  the  superficial  nerves  will  be  subdivided  in'o 
an  ascending  and  descending  series: — the  deep  nerves  into  an  intertial 
and  external  series. 

SUPERFICIAL  BRANCHES  (ASCENDING  SERIES). 

1.  Superficial  Cervical  Nerve. 

This  nerve,  fig.  3.58,  ramifies  in  front  of  the  sterno-mastoid  muscle. 
It  takes  origin  from  the  second  and  third  cervical  nerves,  turns  for- 
ward over  the  sterno-mastoid  about  its  middle,  and,  after  perforating 
the  cervical  fascia,  divides  beneath  the  platysma  myoides  into  two 
branches,  which  are  distributed  to  the  anterior  and  lateral  part  of  the 

* Valentin  notices  filaments  distributed  to  the  articulation  of  the  occipital  bone  with  the 
atlas,  and  to  the  mastoid  process  of  the  temporal  bone. 


SMALL  OCCIPITAL  MERVE. 


303 


neck.  This  nerve  may  be  represented  by  twm  or  more  cords,  the 
branches  into  which  it  divides  w'hen  a single  nerve  being  distinct  one 
from  the  other  from  their  commencement  in  the  plexus.* 

The  upper  branch  gives  an  ascending  offset  with  the  external  jugular  vein,  and 
communicates  freely  with  the  facial  nerve  (cervico-facial  division) ; it  is  then 
transmitted  through  the  platysma  to  the  surface,  supplies  that  muscle,  and  rami- 
fies in  the  integument  of  the  upper  half  of  the  neck  on  its  fore  part,  filaments 
reaching  as  far  as  the  lower  maxilla.  The  lower  branch  likewise  pierces  the 
platysma,  and  is  distributed  below  the  preceding  branch,  its  filaments  extending 
as  low  as  the  sternum. 

While  the  superficial  cervical  nerve  ramifies  over  the  platysma  myoides,  the 
facial  nerve  is  beneath  the  muscle. — According  to  Valentin  many  anastomotic 
arches  are  formed  on-  the  side  of  the  neck  between  those  two  nerves,  as  well  as 
between  the  branches  of  the  former,  one  with  the  other. 

2.  Great  Auricular  Nerve. 

This  nerve  (n.  auricularis  magnus)  (fig.  358,^,)  winds  round  the 
outer  border  of  the  sterno-mastoid,  and  is  directed  obliquely  upwards 
beneath  the  platysma  myoides,  between  the  muscle  and  the  fascia 
of  the  neck,  to  the  lobe  of  the  ear.  Here  the  nerve  gives  a few  small 
offsets  to  the  face,  and  ends  in  auricular  and  mastoid  branches. 

The  auricular  branches  are  directed  to  the  back  of  the  external  ear,  on  which 
they  ramify,  and  are  connected  with  the  branches  derived  from  the  facial  and 
pneumogastric  nerves.  One  of  these  branches  reaches  the  outer  surface  of  the 
ear  by  a fissure  between  the  anti-helix  and  the  concha.  A few  filaments  are 
supplied  to  the  outer  part  of  the  lobule  likewise. 

The  mastoid  brancJi  is  united  to  the  posterior  auricular  branch  of  the  facial  neium, 
and  ascends  over  the  mastoid  process  to  the  integument  behind  the  ear. 

The  branches  of  the  great  auricular  nerve  which  e.xtend  to  the  integuments  of 
the  face  pass  over  the  parotid  gland.  Sorne  slender  filaments  penetrate  deeply 
through  the  substance  of  the  gland,  and  communicate  with  the  facial  nerve. 

3.  Small  Occipital  Nerve. 

The  smaller  occipital  nerve  (n.  occipitalis  minor)  (fig.  358,“,)  varies 
in  size,  and  is  sometimes  double.  It  springs  from  the  second  cervical 
nprvc,  and  is  directed  almost  vertically  to  the  head,  along  the  poste- 
rior border  of  the  sterno-mastoid  muscle.  Having  perforated  the  deep 
fascia  near  the  cranium,  the  small  occipital  nerve  is  continued  up- 
wards between  the  ear  and  the  great  occipital  nerve,  and  ends  in 
cutaneous  filaments  w'hich  extend  higher  than  the  ear,  and  communi- 
cate with  offsets  from  the  larger  occipital  nerve,  as  well  as  with  the 
posterior  auricular  branch  of  the  facial.  It  appears  to  supply  the 
occipito-frontalis  muscle.f 

From  the  small  occipital  nerve  near  the  ear  is  given  an  auricular  branch  (ram. 
auricularis  superior  posterior),  which  is  distributed  to  the  upper  part  of  the  ear 
on  its  posterior  aspect,  and  to  the  elevator  muscle  of  the  auricle.  This  auricular 
branch  is  an  offset  from  the  great  occipital  nerve,  when  the  smcill  occipital  has 
less  than  its  usual  size. 

* Valentin  describes  three  superficial  cervical  nerves,  which  he  names  superior,  middle, 
and  inferior.  Soemmerring  v.  Bau,"  &,c. 

t According  to  Valentin  (op.  cit.)  the  small  occipital  nerve  gives  branches  to  theoccipito. 
frontalis  muscle,  and  reaches  the  upper  part  of  the  head.  The  same  anatomist  further 
states  that  conne.vions  take  place  between  (he  occipital  and  auricular  nerves,  some  being 
placed  over,  and  some  beneath  the  occipito-frontalis  muscle. 


304 


PHRENIC  NERVE. 


SUPERFICIAL  BRANCHES  OF  THE  CERVICAL  PLEXUS 
(DESCENDING  SERIES). 

Supraclavicular  Nerves. 

The  descending  series  of  the  superficial  nerves,  fig.  358,  are  thus 
named.  There  are  two  of  these  nerves,  or,  in  some  cases,  a greater 
number.  They  arise  from  the  third  and  fourth  cervical  nerves,  and 
descend  in  the  interval  between  the  sterno-mastoid  and  the  trapezius 
muscles.  As  they  approach  the  clavicle,  the  nerves  are  augmented  to 
three  or  more  in  number,  and  are  recognised  as  internal,  middle  and 
posterior. 

The  inner  (sternal)  branch,  which  is  much  smaller  than  the  rest,  ramifies  over 
the  inner  half  of  the  clavicle,  and  terminates  near  the  sternum.. 

The  middle  branch,  lying  opposite  the  interval  between  the  pectoral  and  deltoid 
muscles,  distributes  some  offsets  over  the  fore  part  of  the  deltoid,  and  others  over 
the  pectoral  muscle.  The  latter  join  the  small  cutaneous  offsets  of  the  intercostal 
nerves. 

The  posterior  branch  (acromial)  is  directed  outwards  over  the  acromion  and  the 
clavicular  attachment  of  the  trapezius  muscle,  and  ends  in  the  integument  of  the 
upper  and  back  part  of  the  shoulder. 

DEEP  BRANCHES  OF  THE  PLEXUS— INNER  SERIES. 

1.  Connecting  Branches. 

The  cervical  plexus  is  connected  near  the  base  of  the  skull  with  the  trunks  of 
the  pneumogastric,  hypoglossal,  and  sympathetic  nerves,  by  means  of  filaments 
intervening  between  these  nerves  and  the  loop  formed  by  the  first  two  cervical 
nerves  in  front  of  the  atlas.  (See  p.  301.) 

2.  Muscular  Branches. 

a.  Branches  are  supplied  to  the  anterior  recti  muscles ; they  proceed  from  the 
cervical  nerves  close  to  the  vertebrae,  including  the  loop  between  the  first  two  of 
these  nerves  {ante,  page  301). 

b.  Other  branches,  two  in  number,  are  connected  with  the  descending  branch 
of  the  hypoglossal  nerve  (r.  descendens  noni),  forming,  with  that  nerve,  a small 
ple.xus  from  which  the  muscles  below  the  os  hyoides  are  supplied  (see  ante,  page 
293).  One  of  the  branches  is  derived  from  the  second  cervical  nerve,  and  the 
other  from  the  third.  Both  branches  cross  inwards  either  over,  or,  it  may  be, 
under  the  internal  jugular  vein,  (the  position  varying  in  different  cases,)  and  unite 
with  the  branch  of  the  hypoglossal.  The  junction  between  these  nerves  takes 
place  usually  in  front  of  the  sheath  of  the  large  blood-vessels ; but  in  some  cat-es 
it  is  within  the  sheath.  The  position,  in  either  case,  is  determmed  by  that  of  the 
branch  from  the  hypoglossal  nerve.* 

3.  Phrenic  Nerve. 

The  diaphragmatic  or  phrenic  nerve,  the  special  nerve  of  the  dia- 
phragm, courses  through  the  thorax  to  its  destination. 

It  commences  by  two  roots  from  the  third  and  fourth  cervical 
nerves,  and  receives  usually  another  fasciculus  from  another  of  these 
nerves  (the  fifth).  As  it  descends  in  the  neck,  the  nerve  is  inclined 
inwards  over  the  anterior  scalenus  muscle;  and  near  the  chest,  it  is 

* M.  Cniveilhier  describes  an  interchange  of  fibres  at  the  place  of  connexion ; so  that  a 
filament  of  the  spinaj  nerve  is  directed  upwards  along  the  branch  of  the  hypoglossal,  and 
vice  versa. 


CERVICAL  PLEXUS— MUSCULAR  BRANCHES. 


305 


joined  by  a filament  of  the  sympathetic,  sometimes  also  by  another 
filament  derived  from  the  fifth  and  sixth  cervical  nerves. 

As  it  enters  the  thorax  each  phrenic  nerve  is  placed  between  the 
subclavian  artery  and  vein,  and  crosses  over  the  internal  mammary 
artery  near  its  root.  Through  that  cavity  each  takes  nearly  a straight 
direction,  in  front  of  the  root  of  the  lung  on  its  own  side,  and  along 
the  side  of  the  pericardium, — between  this  and  the  mediastinal  part  of 
the  pleura.  Near  the  diaphragm  it  divides  into  branches,  which  sepa- 
rately penetrate  the  fibres  of  that  muscle,  and  then  diverging  one 
from  the  other,  are  distributed  on  its  under  surface. 

The  two  phrenic  nerves  differ  in  their  connexions  at  the  upper  part 
of  the  thorax,  and  somewhat  in  their  length  likewise. 

The  right  nerve  is  placed  more  deeply  than  the  left,  and  is  at  first 
directed  along  the  outer  side  of  the  right  innominate  vein,  and  the  de- 
scending vena  cava.  The  nerve  of  the  left  side  is  a little  the  longer 
of  the  two,  in  consequence  of  the  oblique  position  of  the  pericardium 
round  which  it  winds,  and  also  because  of  the  diaphragm  being  lower 
on  this  than  on  the  opposite  side.  This  nerve  crosses  in  front  of  the 
aorta,  and  the  pulmonary  artery. 

Besides  the  terminal  branches  supplied  to  the  diaphragm,  each  phrenic  nerve 
gives  filaments  to  the  pericardium,  and  receives  sometimes  an  offset  from  the 
union  of  the  descendens  noni  with  the  spinal  nerves.* 

One  or  two  filaments  of  the  nerve  of  the  right  side  join  in  a small  ganglion 
with  diaphragmatic  branches  of  the  solar  plexus  ; and  from  the  ganglion  offsets 
are  given  to  the  supra-renal  capsule,  the  left  hepatic  plexus,  and  the  lower  vena 
cava.  On  the  left  side  there  is  a junction  between  the  same  two  nerves  near  the 
openings  in  the  diaphragm  for  the  oesophagus  and  the  aorta,  but  without  the  ap- 
pearance of  a ganglion. 

DEEP  BRANCHES  OF  THE  PLEXUS— EXTERNAL  SERIES. 

These  nerves  are  distributed  to  muscles  on  the  side  of  the  neck,  and 
some  are  connected  freely  with  the  spinal  accessory  nerve. 

Muscular  Branches. 

The  sterno-mastoid  receives  a branch  from  the  second  cervical  nerve.  Two 
other  branches  proceed  from  the  third  nerve  to  the  levator  angidi  scapula ; and 
from  the  cervical  nerves,  as  they  leave  .the  spinal  canal,  branches  are  given  to 
the  middle  scalenus 'muscle.  Further  the  trapezius  has  branches  prolonged  to  it, 
and  thus,  like  the  stemo-mastoid,  this  muscle  receives  nerves  both  from  the  spi- 
nal accessory  and  the  cervical  plexus. 

Connexion  ivith  the  spinal  accessory  nerve. — This  nenm  is  connected  with  the 
branches  of  the  cervical  plexus  furnished  to  the  sterno-mastoid, — in  the  substance 
of  the  muscle ; also  with  the  branches  distributed  to  the  trapezius, — the  connexion 
between  the  nerves  being  beneath  this  muscle,  and  having  the  appearance  of  a 
plexus ; and  with  another  offset  of  the  cervical  plexus  in  the  interval  between  the 
two  muscles. 

Summary  of  the  cervical  plexus. — From  the  cervical  plexus  are  dis- 
tributed cutaneous  nerves  to  the  back  of  the  head,  part  of  the  ear  and 
face,  and  to  the  anterior  half  of  the  neck.  The  muscles  supplied  from 
the  plexus,  are  the  sterno-mastoid,  the  anterior  recti,  the  levator  anguli 

* Mr.  Swan  notices  this  union  as  occurring  only  on  the  left  side. — Valentin  mentions 
other  filaments  supplied  by  the  phrenic  nerve  to  the  remains  of  the  thymus  gland,  the 
phrenic  vessels,  and  the  anterior  pulmonary  plexus. 

2b* 


306 


BRACHIAL  PLEXUS-BRANCHES. 


scapulae,  the  trapezius,  the  scalenus  posticus^  and  the  diaphragm.  By 
means  of  its  branches  the  plexus  communicates  with  the  pneumogas- 
tric,  spinal  accessory,  hypoglossal,  and  sympathetic  nerve. 

ANTERIOR  DIVISIONS  OF  THE  LOWER  FOUR  CERVICAL  NERVES. 

The  anterior  divisions  of  the  four  lower  cervical  nerves  appear  be- 
tween the  scaleni  muscles,  and  go  to  form  the  brachial  plexus.  They 
are  much  larger  than  the  corresponding  divisions  of  the  upper  cervical 
nerves,  and  the  manner  in  which  they  join  to  form  the  plexus  is  dif- 
ferent. Each  of  these  nerves  is  connected  by  a filament  with  the 
sympathetic, — the  part  of  that  nerve  in  the  immediate  neighbourhood 
of  each,  i.  c.,  with  one  of  the  two  lower  cervical  ganglia,  or  the  plexus 
on  the  vertebral  artery. 

BRACHIAL  PLEXUS. 

This  large  plexus,  from  which  the  nerves  of  the  upper  limb  are 
supplied,  is  formed  by  the  union  of  the  anterior  divisions  of  the  four 
lower  cervical  and  the  first  dorsal  nerves;  and  it  further  receives  a 
fasciculus  from  the  last  of  the  nerves  (fourth)  which  go  to  form  the 
cervical  plexus.  The  plexus  reaches  from  the  lower  part  of  the  neck 
to  the  axillary  space,  where  it  terminates  opposite  the  coracoid  pro- 
cess of  the  scapula  in  large  offsets  for  the  supply  of  the  limb.  From 
the  interval  between  the  anterior  and  middle  scaleni  muscles,  the 
nerves  descend  beneath  the  clavicle,  lying  at  first  on  the  outer  side  of 
the  large  artery  (subclavian  and  axillary),  and  afterwards  in  more 
close  connexion  with  the  vessel.  In  the  neck  they  have  little  of  a 
plexiform  arangement,  but  they  enter  into  various  connexions  in  the 
axilla,  and  to  the  aggregate  of  all,  the  term  brachial  plexus  is  applied. 

The  manner  in  which  the  nerves  are  disposed  in  the  ple.xus  is  liable  to  some 
variation,  but  the  following  may  be  regarded  as  the  arrangement  most  frequently 
met  with.  The  fifth  and  sixth  cervical  are  joined  at  the  outer  border  of  the  sca- 
lenus, and  then  receive  the  seventh  nerve, — the  three  nerves  giving  rise  to  one 
great  cord;  the  eighth  cervical  and  the  first  dorsal  nerves  are  united  in  another 
cord  whilst  they  are  between  the  scaleni  muscles ; the  two  cords  thus  formed  lie 
side  by  side,  and  at  the  outer  side  of  the  axillary  vessels.  Lastly,  a third  cord  is 
produced  opposite  the  clavicle,  or  a little  lower  than  this,  by  the  union  of  a fas- 
ciculus from  each  of  the  other  two.  The  three  cords  of  which  the  plexus  now 
consists,  are  placed  as  follows : — one  on  the  outer  side  of  the  axillary  artery,  one 
on  its  inner  side,  and  one  behind  that  vessel.  The  large  nervous  cords  which 
constitute  the  plexus  at  its  lower  end  are  continued  into  the  branches  which  sup- 
ply the  arm. 

Branches. — The  branches  furnished  by  the  foregoing  nerves  are 
numerous,  and  may  be  conveniently  divided  into  two  classes — viz., 
those  that  arise  above  the  clavicle,  and  those  that  take  origin  below 
the  bone. 

A.  BRANCHES  ABOVE  THE  CLAVICLE. 

The  branches  which  arise  from  the  nerves  before  their  union  into  a 
plexus,  end  in  the  muscles  of  the  shoulder  and  the  side  of  the  chest, 
with  the  exception  of  the  communicating  fasciculus  to  join  the  phrenic 
nerve. 

Branch  to  join  the  Phrenic  Nerve. — This  small  branch  is  an  offset  from  the  fifth 
cervical  nerve ; it  joins  the  phrenic  nerve  on  the  anterior  scalenus  muscle. 


BRACHIAL  PLEXUS— BRANCHES. 


307 


Branches  for  the  Scaleni  and  Longus  Colli  Muscles. — These  nerves  spring  in  an 
irregular  manner  from  the  lower  cervical  nerves  close  to  their  place  of  emergence 
from  the  vertebral  foramen. 

The  branch  for  the  rhomboid  muscle  arises  from  the  fifth  nerve,  and  is  directed 
backwards  to  the  base  of  the  scapula  through  the  fibres  of  the  middle  scalenus, 
and  beneath  the  levator  anguli  scapulae.  It  is  distributed  to  the  under  surface  of 
the  rhomboid  muscle,  and  gives  sometimes  a branch  to  the  levator  scapulae. 

The  nerve  of  the  svhclavius  muscle,  of  small  size,  begins  in  the  cord  which  results 
from  the  union  of  the  fifth  and  sixth  cervical  nerves.  It  is  directed  over  the  outer 
part  of  the  subclavian  artery  to  the  under  surface  of  the  subclavius  muscle.  This 
little  nerve  is  commonly  connected  with  the  phrenic  nerve  in  the  neck  or  in  the 
chest,  by  means  of  a slender  filament. 

Posterior  Thoracic  Nerve. 

The  posterior  thoracic  nerve  (external  respiratory  of  Bell)  is  dis- 
tributed exclusively  to  the  large  serratus  muscle.  Formed  in  the  sub- 
stance of  the  middle  scalenus  muscle  by  two  roots,  one  from  the  fifth 
and  one  from  the  sixth  nerve,  it  reaches  the  surface  of  that  muscle, 
lower  than  the  nerve  of  the  rhomboid  muscle,  and  is  often  connected 
with  that  nerve.  After  emerging  from  the  scalenus  muscle,  the  pos- 
terior thoracic  nerve  descends  behind  the  brachial  plexus  on  the  outer 
surface  of  the  serratus  magnus,  and  extends  nearly  to  the  lower  bor- 
der of  this  muscle,  supplying  it  with  several  branches  (fig.  367). 

Suprascapular  Nerve. 

The  suprascapular  nerve  arises  from  the  first  cord  of  the  plexus,  and 
bends  beneath  the  trapezius  to  the  dorsal  surface  of  the  scapula,  where 
it  is  placed  between  the  muscles  and  the  bone.  Entering  the  supra- 
spinous fossa  of  the  scapula,  through  the  notch  in  its  upper  border, 
(beneath  the  ligament  which  crosses  the  notch,)  the  suprascapular 
nerve  supplies  two  branches  to  the  supraspinatus,  one  being  near  the 
upper,  the  other  one  near  the  lower  part  of  the  muscle;  and  it  is  then 
transmitted  in  front  of  the  spine  of  the  scapula  to  the  infraspinous 
fossa,  where  it  ends  in  the  infraspinatus  muscle.  In  the  upper  fossa  of 
the  scapula,  a slender  articular  filament  is  given  to  the  shoulder-joint, 
and  in  the  lower  fossa  other  offsets  enter  the  same  joint  and  the  bone 
(scapula). 

B.  BRANCHES  GIVEN  FROM  THE  BRACHIAL  PLEXUS  BELOW  THE 

CLAVICLE. 

These,  the  remaining  offsets  of  the  brachial  plexus,  supply  muscles 
on  the  fore  part  of  the  chest,  some  of  the  muscles  and  integument  of 
the  shoulder,  and  the  remainder)!’  he  upper  limb. 

Origin  of  nerves  from  the  plexu  —The  several  nerves  now  to  be 
described  are  derived  from  the  three  great  cords  of  the  plexus  in  this 
order : 

From  the  outer  cord, — the  external  of  the  two  anterior  thoracic  nerves,  the 
outer  head  of  the  median,  and  the  musculo-cutaneous. 

From  the  inner  cord,-r-the  inner  of  the  two  anterior  thoracic,  the  internal  cuta- 
neohs  and  ulnar,  the  nerve  of  Wrisberg,  and  the  inner  head  of  the  median. 

From  the  posterior  cord, — the  subscapular  nerves,  the  musculo-spiral,  and  the 
circumflex. 

The  nerves  traced  to  the  spinal  nerves. — If  the  fasciculi,  of  which  the  principal 
nerves  are  composed,  be  followed  through  the  plexus,  they  may  be  traced  to  the 
spinal  nerves  named  for  each  in  the  subjoined  table.  The  higher  numbers  refer 
to  the  cervical  nerves,  the  unit  to  the  dorsal  nerve : — 


308 


CIRCUMFLEX  NERVE. 


Subscapular  from  . . . 

Circumflex 

Internal  cutaneous  . . . 

Smaller  internal  cutaneous 


. 5.6.7.8. 

( 5.6.7.  or 
( 5.6.7.8.I. 

. . , 8.1. 

. . . 8.1. 


External  cutaneous 


from  . . 

Ulnar  nerve 

Median  nerve  . 
Musculo-spiral 


. 5.6.7. 

( 5.6.7 .8.1.  or 
( 7.8.1.  or  8.1 

( 5.6.7 .8.1.  or 
I 5.6.7.8. 

6.7.8. 


Some  difference  will  be  found  between  the  statements  of  anatomists  who  have 
investigated  the  point — for  instance,  Scarpa  {-‘Annotationes  Anatom")  and  Kro- 
nenberg,  (“  Plcx.  nervor.  Structura  et  Virtutes”) — with  respect  to  the  nerves  to 
which  the  branches  are  assigned.  Such  difference  is,  doubtless,  owing  to  the 
variation  which  actually  exists  in  different  cases. 


Anterior  Thoracic  Nerves. 

The  anterior  thoracic  nerves,  two  in  number,  supply  the  pectoral 
muscles.  They  are  distinguished  as  external  and  internal. 

a.  The  external,  or  more  superficial  branch,  crosses  inwards  over  the  axfllaiy 
artery,  and  terminates  in  the  great  pectoral  muscle. 

h.  The  internal,  or  deeper  branch,  comes  forward  between  the  axillary  artery 
and  vein  to  the  small  pectoral  muscle,  and  is  joined  by  a branch  from  the  preced- 
ing. This  nerve  presents  a plexiform  division  beneath  the  small  pectoral  muscle, 
and  supplies  branches  to  it  and  to  the  larger  pectoral  muscle.— The  two  preceding 
nerves  are  connected  by  a filament  which  forms  a loop  over  the  artery  at  its 
inner  side. 

Subscapular  Nerves. 

These  nerves  are  three  in  number.  They  are  distinguished  as 
upper,  lower,  and  long  subscapular,  and  are  destined  for  the  subscapu- 
laris,  teres  major,  and  latissimus  dorsi  muscles. 

a.  The  upper  nerve,  the  smallest  of  the  subscapular  nerves,  penetrates  the 
upper  part  of  the  subscapular  muscle,  b.  The  lower  nerve  gives  a branch  to  the 
same  muscle  at  its  axillary  border,  and  ends  in  the  teres  major  muscle.  There  is 
sometimes  a distinct  nerve  for  the  last-named  muscle,  c.  The  long  subscapuhr 
nerve,  the  largest  of  the  three,  runs  along  the  lower  border  of  the  subscapular 
muscle  to  the  latissimus  dorsi,  to  which  it  is  distributed. 


Circumflex  Nerve. 

The  circumflex  or  axillary  nerve  (fig.  364)  gives  both  muscular  and 
cutaneous  nerves  to  the  shoulder.  At  first  this  nerve  is  placed  behind 
the  axillary  artery,  but  at  the  lower  border  of  the  subscapular  muscle 
it  is  inclined  backwards,  and  separates  into  an  upper  and  a lower 
division. 

The  upper  division  winds  around  the  neck  of  the  humerus,  extending  to  the 
anterior  border  of  the  deltoid  muscle,  which  covers  it.  Branches  are  distributed 
to  that  muscle  j and  one  or  two  cutaneous  filaments,  after  penetrating  the  muscular 
fibres,  are  bent  downwards,  and  supply  the  integument  over  the  lower  part  of  the 
muscle. 

The  lower  division  of  the  circumflex  nerve  supplies,  near  its  commencement, 
branches  to  the  teres  minor  and  to  the  back  part  of  the  deltoid,  the  nerve  given  to 
the  former  muscle  presenting  a gangliform  enlargement.  It  is  then  directed  for- 
wards on  the  cutaneous  surface  of  the  deltoid,  below  its  middle,  and  after  perfo- 
rating the  deep  fascia,  ramifies  in  the  integument  over  the  lower  two-thirds  of  the 
muscle  (fig.  365,’),  one  branch  extending  to  the  integument  over  the  longhead  of 
the  triceps  muscle. 

An  articular  filament  for  the  shoulder-joint  arises  from  the  circumflex  nerve  near 
its  commencement.  It  continues  with  the  trunk  of  the  nerve  to  the  lower  border 
of  the  scapula,  and  enters  the  capsular  ligament  below  the  subscapular  muscle. 


SMALL  INTERNAL  CUTANEOUS  NERVE. 


309 


Internal  Cutaneous  Nerve. 


At  its  origin  from  the  brachial  plexus,  this 
nerve  is  placed  on  the  inner  side  of  the  axillary 
artery.  As  it  descends,  it  approaches  the  sur- 
face, and  becomes  cutaneous  about  the  middle  of 
the  arm.  After  perforating  the  fascia — or  in 
some  cases,  before  it  has  penetrated  that  mem- 
brane— the  internal  cutaneous  nerve  is  divided 
into  two  parts ; one  (the  outer  part)  being  des- 
tined for  the  anterior,  the  other  for  the  posterior 
surface  of  the  fore-arm. 

The  external  branch,  fig.  363,“  crosses,  at  the  bend  of 
the  elbow,  over  (in  some  cases  behind)  the  median  basi- 
lic vein.  Below  the  elbow-joint,  this  branch  is  placed  in 
front  of  the  lore-arm — towards  its  inner  side,  with  the 
cutaneous  veins,  and  distributes  filaments  as  far  as  the 
wrist;  one  of  these  is,  in  some  instances,  joined  with 
a cutaneous  branch  of  the  ulnar  nerve  (fig.  363,“). 

The  internal  branch  of  the  nerve,’’  inclines  obliquely 
downwards,  at  the  inner  side  of  the  basilic  vein,  and 
winding  to  the  back  of  the  fore-arm,  over  the  prominence 
of  the  internal  condyle  of  the  hurtierus,  extends  some- 
what below  the  middle  of  the  fore-arm,  fig.  365.7  Above 
the  elbow  this  branch  is  connected  with  the  smaller  in- 
ternal cutaneous  nerve,  (nerve  of  Wrisberg,)  and  after- 
wards communicates  with  the  outer  division  of  the  inter- 
nal cutaneous.* 

■ Near  the  axilla  the  internal  cutaneous  gives  an  offset 
(fig.  363,“)  through  the  fascia  to  the  integ-ument  of  the 
arm.  This  small  branch  lies  a little  to  the  outer  side  of 


Fig.  363. 


the  nerve  from  which  it  springs,  and  reaches  to,  or  nearly 
to,  the  elbow,  distributing  filaments  outwards  to  the  in- 
tegument over  the  biceps  muscle.  The  same  branch  is 
often  connected  with  the  intercosto-humeral  nerve. 

Summary. — The  internal  cutaneous  nerve  gives 
filaments  to  the  inner  and  fore  part  of  the  arm, 
and  to  the  inner  part  of  the  fore  arm,  on  the  ante- 
rior and  the  posterior  surface.  Its  offsets  are 
connected  with  the  smaller  internal  cutaneous 
nerve,  and  with  the  ulnar  nerve. 


Plan  of  the  cutaneous 
nerves  on  the  front  of  the 
arm.  — 1.  Supraclavicular 
ner  ves.  2.  Branches  of  the 
circumflex  nerve.  3.  Ex- 
ternal cutaneous  (upper 
branch)  of  the  musculo- 
spiral  nerve.  4.  Musculo- 
ciiianeous.  5.^  Branch  of 
ulnar  nerve.  6.  Internal 
cutaneous;  external  branch. 
7.  Inner  branch  of  that 
nerve.  8.  Offset  to  the 
upper  arm  from  same.  9. 
Nerve  of  Wrisberg.  10. 
Intercosto-humeral  nerve. 


Small  Internal  Cutaneous  Nerve. 

The  smaller  internal  cutaneous  nerve  (nerv.  cutaneus  internus  minor 
vel  ulnaris  Wrisbergii, — Klint,f),  (fig.  SOS,**)  assists  the  larger  internal 
cutaneous  nerve  in  supplying  the  inner  side  of  the  arm. 

This  nerve  commonly  arises  from  the  inner  cord  of  the  brachial 

* Mr.  Swan  describes  a connexion  near  the  wrist  between  this  branch  and  the  dorsal 
branch  of  the  ulnar  nerve. 

t This  nerve  appears  to  have  been  first  made  known  by  Wrisberg,  in  his  lectures;  and 
the  first  published  account  of  it  is  contained  in  an  Essay  by  one  of  his  pupils;  see  Klint, 
“ Ue  Nervis  Brachii,”  in  Ludwig  “Script.  Nevrol.  min."  tom.  iii. 


310 


MUSCULO-CUTANEOUS  NERVE. 


plexus  in  connexion  with  the  larger  internal  cutaneous  and  the  ulnar 
nerves;  but  it  is  sometimes  derived  from  the  posterior  cord  of  the 
plexus  with  the  musculo-spiral  and  circumflex  nerves.  In  the  axilla, 
the  nerve  of  Wrisberg  is  concealed  at  first  by  the  axillary  vein,  but  it 
soon  appears  on  the  inner  side  of  that  vessel,  and  communicates  with 
the  intercosto-humeral  nerve.  It  is  then  placed  along  the  inner  side  of 
the  brachial  vessels  to  about  the  middle  of  the  arm,  where  it  pierces  the 
fascia,  and  is  continued  immediately  beneath  the  integument  to  the 
interval  between  the  internal  condyle  of  the  humerus  and  the  olecra- 
non, fig.  365,®. 

Branches. — In  the  lower  third  of  the  arm,  branches  of  this  little  nerve  are  directed 
almost  horizontally  to  the  integument  on  its  posterior  aspect ; and  the  nerve  ends 
at  the  elbow,  by  dividing  into  several  filaments,  some  of  which  are  directed  for- 
wards over  the  inner  condyle  of  the  humerus,  while  others  are  prolonged  down- 
wards behind  the  olecranon. 

Connexion  ivith  intercosto-humeral  nerve. — ^The  connexion  between  the  nerve  of 
Wrisberg  and  the  intercosto-humeral  nerve  presents  much  variety  in  different 
cases : — in  some,  there  are  two  or  more  intercommunications,  forming  a kind  of 
plexus  on  the  posterior  boundary  of  the  axillary  space;  in  others,  the  intercosto- 
humeral  nerve  is  of  larger  size  than  usual,  and  takes  the  place  of  the  nerve  of 
Wrisberg,  only  receiving  in  the  axilla  a small  filament  from  the  brachial  plexus, 
and  this  small  communicating  filament  represents  in  such  cases  the  nerve  of 
Wrisberg. 

Summary. — The  nerve  of  Wrisberg  is  the  cutaneous  nerve  of  the 
lower  half  of  the  upper  arm  on  its  inner  and  posterior  aspect.  It  sup- 
plies the  skin  below  the  cutaneous  branch  of  the  musculo-spiral  nerve. 

Musculo-cutaneous  Nerve. 

The  musculo-cutaneous  or  external  cutaneous  nerve  (fig.  364d) 
supplies  branches  to  the  muscles  of  the  arm,  and  to  the  integument  of 
the  fore-arm.  It  is  deeply  placed  between  the  muscles  as  far  as  the 
elbow,  and  below  this  point  is  immediately  under  the  integument. 

Muscular  part. — Arising  from  the  brachial  plexus  opposite  the  small 
pectoral  muscle,  this  nerve  perforates  the  coraco-brachialis  muscle;* 
and  passing  obliquely  across  the  arm  between  the  biceps  and  brachialis 
anticus  muscles,  reaches  the  outer  side  of  the  limb  a little  above  the 
elbow'.  Here  it  perforates  the  fascia  and  commences  its  subcutaneous 
course  on  the  fore-arm,  which  will  presently  be  described. 

Branches. — As  it  descends  through  the  arm,  the  nerve  distributes  branches  to 
the  muscles  as  follows ; — Before  it  reaches  the  coraco-brachialis,  one  branch  is 
given  to  that  muscle  and  to  the  short  head  of  the  biceps;  and  other  filaments  are 
furnished  to  the  coraco-brachialis,  while  the  nerve  lies  within  its  fibres.  Lower 
down,  where  the  nerve  is  placed  between  the  biceps  and  brachialis  anticus, 
branches  are  supplied  to  both  those  muscles.  Lastly,  the  humerus  and  the  elbow- 
joint  receive  small  filaments  from  the  same  source. 

The  CUTANEOUS  PART  of  the  musculo-cutaneous  nerve,  fig.  363,^ 

* The  nerve  is  sometimes  named  “ perforans  Casserii,”  the  first  term  of  this  designation 
having  reference  to  the  mode  in  which  the  nerve  is  connected  with  the  coraco-braehiulis 
muscle.  As  regards  the  assoeiation  of  the  name  of  Casserius  with  the  musculo-cutaneous 
nerve,  it  should  be  mentioned  that  this  anatomist  named  the  muscle  “ perforatus,”  but  he 
does  not  appear  to  have  distinguished  the  nerve  in  the  manner  which  seems  to  be  implied. 
See  “Julii  Casserii  Placentini  Tab.  Anatom. (D.  Bucretius  explicat.  addidil),  Tab.  l9  and 
20.  Franeforti,  1632. 


ULNAR  NERVE. 


311 


approaching  the  integument  at  the  outer  side  of  the  biceps  muscle, 
and  nearly  opposite  the  elbow-joint,  crosses  behind  the  median  cephalic 
vein,  and  inclining  outwards,  divides  into  two  branches,  which  supply 
the  integument  on  the  outer  side  of  the  fore-arm,  one  on  its  anterior, 
the  other  on  its  posterior  aspect. 

The  anterior  branch  descends  near  the  radial  border  of  the  fore-arm.  It  is  placed 
in  front  of  the  radial  artery  near  the  wrist,  and  distributes  some  filaments  over 
the  ball  of  the  thumb.  Piercing  then  the  fascia,  it  accompanies  the  artery  to  the 
back  part  of  the  carpus.  This  branch  is  connected  at  the  wrist  with  an  offset  of 
the  radial  nerve. 

The  posterior  branch  of  the  external  cutaneous  nerve  is  directed  outwards  to  the 
back  of  the  fore-arm,  and  ramifies  in  the  integument  of  its  lower  third,  extending 
as  far  as  the  wrist,  fig.  365,'".  It  communicates  with  a branch  of  the  radial  nerve, 
and  with  the  external  cutaneous  branch  of  the  musculo-spiral  nerve. 

Some  peculiarities  of  the  nerve. — In  some  cases,  it  does  not  perforate  the  coraco- 
braohialis  muscle.  It  is  from  time  to 


time  found  to  be  an  offset  of  the  median 
nerve;  and  in  this  case,  the  coraco- 
brachialis  muscle  receives  a separate 
branch  from  the  brachial  plexus. 

Summary. — The  musculo-cuta- 
neous  nerve  supplies  three  muscles 
in  front  of  the  humerus,  and  the 
integument  on  the  outer  side  of  the 
fore-arm.  Communications  are  es- 
tablished between  it  and  the  radial 
and  the  external  cutaneous  branch 
of  the  musculo-spiral. 

ULNAR  NERVE.  ' 

The  ulnar  nerve,  (fig.  3G4,?)  sup- 
plies both  muscular  and  cutaneous 
branches  to  the  fore-arm  and  the 
hand.  In  its  whole  course  it  lies 
along  the  inner  (ulnar)  side  of  the 
limb. 

At  its  commencement  the  ulnar 
nerve  lies  at  the  inner  side  of  the 
axillary  artery,  and  retains  the 
same  position  with  respect  to  the 
brachial  vessels  nearly  to  the  mid- 
dle of  the  arm.  From  this  point  it 
gradually  inclines  inwards,  through 
the  internal  intermuscular  septum, 
to  the  interval  between  the  ole- 
cranon and  the  inner  condyle  of 
the  humerus,  and  reaches  the  fore- 

Fig.  364.  A plan  of  the  nerves  of  the  arm.  a. 
Atcillary  artery.  B Brachial  artery.  Nerves:  2. 
Suprascapular.  3.  Suhscapular.  4,  Internal  cuta- 
neous. 5.  Musculo-cutaneous.  6.  Circumflex. 
7.  Ulnar.  8.  Superficial  branch  of  the  same  on 
to  the  hand.  12.  Median.  13.  Anterior  inter- 
osseous. 15.  Musculo-spiral.  16.  Radial.  17. 
Posterior  interosseous. 


Fig.  364. 


312 


ULNAR  NERVE-BRANCHES. 


arm  between  the  two  beads  of  the  flexor  carpi  ulnaris.  From  the 
axilla  to  the  place  at  which  it  sinks  beneath  the  muscle  last  named,  the 
nerve  is  covered  only  by  the  fascia,  and  may  be  felt  through  the  in- 
tegument, a little  above  the  elbow. 

In  the  fore-arm:  The  ulnar  nerve  extending  in  a straight  course  to 
the  outer  side  of  the  pisiform  bone  of  the  carpus,  is  concealed  by  the 
flexor  carpi  ulnaris,  as  far  as  the  middle  of  this  part  of  the  limb ; and 
thence  onwards,  it  lies  at  the  outer  side  of  the  same  muscle,  covered 
only  by  the  integument  and  fascia.  In  the  whole  course  from  the 
elbow  to  the  carpus,  it  rests  against  the  deep  flexor  of  the  fingers ; 
and  the  ulnar  artery,  which  is  separated  from  the  nerve  by  a con- 
siderable interval  at  the  elbow,  is  in  contact  with  it  (on  the  outer  side) 
in  the  lower  half  of  the  fore-arm. 

Branches. — In  its  course  along  the  upper  arm  the  ulnar  nerve  gives 
oft'  no  branch.  The  offsets  derived  from  it  at  the  elbow  and  in  the 
fore-arm,  are  as  follows: — 

1.  Articular  nerves. — These  consist  of  some  small  filaments  supplied  to  the 
elbow-joint,  as  the  nerve  passes  close  behind  the  joint. 

2.  Muscular  branches. — One  branch  enters  the  upper  part  of  the  flexor  carpi 
ulnaris,  and  another  supplies  the  two  inner  divisions  (the  inner  half)  of  the  deep 
flexor  of  the  fingers. 

3. ’  Cutaneous  branches. — These  are  two  smalhnerves  that  arise  about  the  middle 
of  the  fore-arm,  by  a common  trunk.  One  pierces  the  fascia,  and  turning  down- 
wards, joins  a branch  of  the  internal  cutaneous  nerve,  fig.  363, ■*.  This  branch  is 
often  absent.  The  second,  a pafmar  bj-anch,  lies  on  the  ulnar  artery,  which  it 
accompanies  to  the  hand.  This  little  nerve  gives  filaments  around  the  vessel, 
and  ramifies  in  the  integument  of  the  hand,  joining  in  some  cases  with  other 
cutaneous  offsets  of  the  ulnar  or  median  nerve. 

4.  Dorsal  branch  of  the  hand. — This  large  offset,  leaving  the  trunk  of  the  ulnar 
nerve  about  two  inches  above  the  wrist,  winds  backwards  beneath  the  flexor 
carpi  ulnaris,  and  divides  into  branches,  one  of  which  ramifies  on  the  inner  side 
of  the  little  finger,  and  another  divides  to  supply  the  contiguous  sides  of  that 
finger  and  the  ring  finger.  On  the  back  of  the  metacarpus,  this  nerve  joins  with 
an  offset  of  the  radial  nerve,  and  from  the  union  of  the  two,  filaments  are  distri- 
buted to  the  opposed  sides  of  the  ring  finger  and  the  middle  finger.  The  several 
posterior  digital  nerves  now  described  are  united  with  offsets  directed  backwards 
from  the  anterior  digital  nerves  furnished  by  the  median  and  ulnar. 

Articular  nerves. — Besides  the  foregoing  branches,  the  ulnar  nerve  supplies  some 
filaments  to  the  wrist-joint. 

Palmau  part  of  ulnar  nerve. — On  the  annular  ligament,  or  some- 
what beyond  it,  the  nerve  separates  into  two  parts,  one  of  which  is 
superficial,  and  the  other  is  deeply  placed  in  the  hand. 

a.  The  superficial  division  accompanying  the  ulnar  artery,  supplies 
digital  nerves  at  the  inner  side  of  the  hand,  and  gives  likewise  a branc.h 
to  the  palmaris  brevis  muscle,  arid  offsets  to  the  integument.* 

Digital  nerves. — One  of  these  belongs  to  the  ulnar  side  of  the  little  finger,  'fhe 
other  is  connected  in  the  palm  of  the  hand  with  a digital  branch  of  the  median 
nerve,  and  at  the  cleft  between  the  little  and  ring  fingers,  gives  an  offset  to  the 
opposed  sides  of  each.  The  disposition  of  the  digital  branches  on  the  fingers  is 
the  same  as  that  of  the  median  nerve,  to  be  presently  described. 

b.  The  deep  palmar  division  of  the  ulnar  nerve  follows  the  course 

• These  may  be  found  to  communicate  with  the  palmar  nerves  given  from  the  median  | 
or  ulnar. 


MEDIAN  NERVE. 


313 


of  the  deep  palmar  arch  of  vessels,  beneath  the  long  flexor  tendons, 
and  in  contact  with  the  interosseous  muscles. 

Branches. — At  its  commencement,  branches  leave  the  deep  palmar  nerve  to 
supply  the  small  muscles  of  the  little  finger.  As  it  lies  across  the  metacarpal 
bones,  it  distributes  two  branches  to  each  interosseous  space  — one  for  the 
palmar,  the  other  for  the  dorsal  interosseous  muscle ; and  the  branches  of  the 
second  and  third  palmar  interossei  supply  filaments  to  the  innermost  two  lum- 
bricales  muscles.  Opposite  the  space  between  the  thumb  and  the  index-finger, 
the  nerve  ends  in  branches  to  the  adductor  pollicis,  and  the  inner  part  of  the 
flexor  brevis  pollicis. 

Summary. — The  ulnar  nerve  gives  cutaneous  filaments  to  the  lower 
part  of  the  fore-arm  (to  a small  extent),  and  to  the  hand  on  its  palmar 
and  dorsal  aspects.  It  supplies  the  following  muscles,  viz. : — the  ulnar 
flexor  of  the  carpus,  the  deep  flexor  of  the  fingers  (its  inner  half),  the 
short  muscles  of  the  little  finger,  with  the  palmaris  brevis,  the  inner 
part  of  the  short  muscles  of  the  thumb,  and  the,  interosseous  muscles 
of  the  hand,  with  the  two  internal  lumbricales.  Lastly,  it  contributes 
to  the  supply  of  the  elbow  and  wrist-joints. 

MEDIAN  NERVE. 

This  nerve,  fig.  364,  is  placed  along  the  middle  of  the  limb  (whence 
its  name),  and  it  occupies  a position  intermediate  between  the  ulnar 
and  the  musculo-spiral  (with  the  radial)  nerves.  Beginning  by  two 
roots  (one  from  the  outer,  the  other  from  the  inner  cord  of  the  bra- 
chial plexus),  which  unite  before  the  axillary  artery  or  on  its  outer 
side,  the  nerve  is  in  contact  with  that  artery  and  its  continuation,  the 
brachial  artery,  nearly  to  the  elbow.  In  this  position  (near  the  elbow- 
joint)  it  is  placed  at  the  inner  side  of  the  vessel,  having  crossed  ob- 
liquely over  it. 

In  the  fore-akm  : — The  median  nerve,  after  passing  between  the 
two  heads  of  the  pronator  teres,  is  placed  between  the  superficial  and 
the  deep  flexor  muscle?  of  the  fingers,  until  it  arrives  at  the  lower  end 
of  the  fore-arm.  Here  it  is  for  a short  space  covered  only  by  the 
integument  and  the  fascia,  and  it  lies  between  the  radial  flexor  of  the 
carpus,  and  the  superficial  flexor  of  the  fingers.  Finally,  the  nerve 
leaves  the  fore-arm  beneath  the  anterior  annular  ligament  of  the 
carpus. 

Branches. — The  median  nerve  usually  gives  no  offset  in  the  upper 
arm.  In  the  fore-arm  it  distributes  branches  to  the  muscles  in  its  im- 
mediate neighbourhood,  and  a single  cutaneous  filament.  These  are 
disposed  as  follows : 

1.  Muscular  branches. — All  the  muscles  on  the  front  of  the  fore-arm  (pronators 
and  flexors),  except  the  flexor  carpi  ulnaris  and  part  of  the  deep  flexor  of  the 
fingers,  are  supplied  from  the  median  nerve,  and  the  several  branches  separate 
from  the  nerve  near  the  elbow-joint.  The  branch  furnished  to  the  pronator  teres 
often  arises  above  the  joint. 

2.  Anterior  interosseous  nerve. — This  is  the  longest  branch  of  the  median  nerve, 
and  it  supplies  the  deeper  muscles  of  the  fore-arm.  Commencing  at  the  ujrper 
iPart  of  the  fore-arm,  beneath  the  superficial  flexor  of  the  fingers,  the  interosseous 
.nerve  courses  downward  with  the  anterior  interosseous  artery  on  the  interosseous 
membrane,  and  between  the  long  flexor  of  the  thumb  and  the  deep  flexor  of 
'the  fingers,  to  the  pronator  quadratus  muscle,  in  which  it  ends.  Offsets  are  dis- 

voL.  II.  27 


314 


MEDIAN  NERVE— BRANCHES. 


tributed  to  the  two  muscles  between  which  the  nerve  lies  in  its  progress  down- 
wards. 

3.  Cutaneous  palmar  branch. — This  small  nerve  pierces  the  fascia  of  the  fore-arm 
close  to  the  annular  ligament,  and  after  crossing  over  that  ligament,  ends  in  the 
integument  of  the  palm  about  its  middle.  It  is  connected  with  the  cutaneous 
pabnar  branch  of  the  ulnar  nerve,  and  distributes  some  filaments  over  the  ball 
of  the  thumb.  The  filaments  last  referred  to  communicate  with  offsets  of  the 
radial  or  the  e.vterual  cutaneous  nerve. 

The  median  nerve  in  the  hand. — After  passing  from  beneath  the 
annular  ligament  of  the  carpus,  the  median  nerve  is  covered  by  the 
palmar  foscia  with  the  integument,  and  rests  against  the  tendons  of 
flexor  muscles.  Somewhat  enlarged,  and  slightly  reddish  in  colour,  it 
here  separates  into  two  parts  of  nearly  equal  size.  One  of  these  (the 
external  one)  supplies  some  of  the  short  muscles  of  the  thumb,  and 
gives  digital  branches  to  the  thumb  and  the  index  finger;  and  the 
second  division  supplies  the  middle  finger,  and  in  pari  the  index  and 
ring  fingers.  The  branches  thus  indicated  are  distributed  as  fol- 
lows:— 

1.  Branch  to  muscles  of  the  thumb. — This  short  nerve  subdivides  for  the  abductor, 
the  opponens,  and  the  outer  head  of  the  flexor  brevis  j)ollicis  muscle. — The  re- 
mainder of  the  small  mass  of  muscles  of  the  thenar  eminence  (the  part  placed  at 
the  inner  side  of  the  long  flexor  tendon)  is  supplied  by  the  ulnar  nerve. 

2.  Digital  nerves. — The  digital  nerves  are  five  in  number,  and  .belong  to  the 
thumb,  and  the  fingers  as  far  as  the  outer  side  of  the  ring  finger.  As  they  ap- 
proach the  cleft  between  the  fingers,  these  nerves  are  close  to  the  integument  in 
the  intervals  between  the  processes  of  the  palmar  fascia ; the  three  external  re- 
main undivided,  but  the  fourth  and  fifth  bifurcate  and  supply  each  the  contiguous 
sides  of  two  fingers. 

The  first  and  second  nerves  lie  along  the  sides  of  the  thumb,  and  the  former  (the 
outer  one)  is  connected  with  the  radial  nerve  over  the  ball  of  the  thumb. 

The  third,  destined  for  the  radial  side  of  the  index  finger,  gives  a muscular 
branch  to  the  first  or  most  external  lumbricalis  muscle. 

The supplies  the  second  lumbricalis,  and  divides  into  two  branches  for 
the  opposed  sides  of  the  inde.x  and  middle  fingers. 

The  fifth,  the  most  internal  of  the  digital  nerves,  is^onnected  with  the  ulnar 
nerve,  and  splits  to  furnish  a branch  each  to  the  ring  and  middle  fingers. 

Each  digital  nerve  divides  at  the  end  of  the  finger  into  two  branches, 
one  of  which  supplies  the  pulp  on  the  fore  part  of  the  finger;  the  other 
ramifies  beneath  the  nail.  Branches  pass  from  each  nerve  forwards 
and  backwards  to  the  integument  of  the  finger:  and  one  larger  than 
the  rest  inclines  backwards  by  the  side  of  the  first  phalanx  of  the  finger,  'P 
and  after  joining  the  dorsal  digital  nerve,  ends  in  the  integument  over 
the  last  phalanx. 

Summary. — The  median  nerve  gives  cutaneous  branches  to  the 
palm,  and  to  several  fingers.  It  supplies  the  pronator  muscles,  the 
flexors  of  the  carpus,  and  the  long  flexors  of  the  fingers  (except  the 
ulnar  flexor  of  the  carpus,  and  part  of  the  deep  flexor  of  the  fingers), 
and  likewise  the  outer  half  of  the  short  muscles  of  the  thumb,  and  two 
lumbricales. 

Some  similarity  will  be  observed  between  the  course  and  distribu-  j 
tion  of  the  median  and  ulnar  nerves.  Neither  gives  any  offset  in  the 
arm.  Together  they  supply  all  the  muscles  in  front  of  the  fore-arm 
and  the  hand,  and  together  they  supply  the  skin  of  the  palmar  surface 
of  the  hand,  and  impart  tactile  power  to  all  the  fingers. 


k 


MUSCULO-SPIRAL  NERVE— BRANCHES. 


315 


MUSCULO-SPIRAL  NERVE. 

The  musculo-spiral  nerve,  the  largest  offset  of  the  brachial  plexus, 
fig.  364,  occupies  chiefly  the  back  part  of  the  limb,  and  supplies  nerves 
to  the  extensor  muscles,  as  well  as,  to  some  extent,  to  the  skin  like- 
wise. 

At  its  commencement,  this  nerve  is  placed  behind  the  axillary  ves- 
sels. In  its  progress  downwards  it  winds  in  a spiral  manner  (whence 
the  distinctive  name)  from  the  inner  to  the  outer  side  of  the  limb  be- 
hind the  humerus,  between  it  and  the  triceps  muscle.  On  the  outer 
side  of  the  arm  the  nerve  descends  in  the  interval  between  the  supina- 
tor longus  and  brachialis  anticus  muscles,  to  the  outer  condyle  of  the 
humerus,  where  it  ends  by  dividing  into  the  radial  and  posterior  in- 
terosseous nerves. 

The  branches  given  from  the  musculo-spiral  nerve  in  its  course 
through  the  upper  arm,  are  found  on  the  inner  side  of  the  humerus, 
behind  that  bone,  and  on  its  outer  side. 

a.  Internal  branches. — These  consist  of  muscular  and 
cutaneous  branches  : — 

1.  Muscular  branches  for  the  inner  and  middle  heads 
of  the  triceps.  That  for  the  inner  division  of  the  muscle 
is  long  ahd' slender;  it  lies  by  the  side  of  the  ulnar 
nerve,  and  reaches  as  far  as  the  lower  third  of  the  upper 
arm. 

2.  The  internal  cutaneous  branch  of  the  musculo-spiral 
nerve,  fig.  365,®,  commonly  unites  in  origin  with  the 
preceding.  It  winds  backwards  beneath  the  intercosto- 
humeral  nerve,  and  after  supplying  offsets  to  the  skin, 
ends  about  two  inches  from  the  olecranon ; in  some 
bodies  it  extends  as  far  as  the  olecranon.  This  nerve  is 
accompanied  by  a small  cutaneous  artery. 

b.  Posterior  branches.  — Whilst  the  musculo-spiral 
nerve  is  between  the  triceps  muscle  and  the  humerus, 
it  gives  off  a large  fasciculus,  which  subdivides  into 
muscular  branches. — These  muscular  branches  supply 
the  outer  head  of  the  triceps  muscle  and  the  anco- 
neus. The  branch  of  the  anconeus  is  remarkable  for  its 
length,  being,  at  the  same  time,  slender;  it  descends 
in  the  substance  of  the  triceps,  to  the  interval  between 
the  outer  condyle  of  the  humerus  and  the  olecranon, 
to  terminate  in  the  muscle  for  which  it  is  destined. 

c.  External  branches. — This  series  comprises  branches 
to  muscles  and  long  cutaneous  branches.— 1.  The  Mus- 
cular branches^  supply  the  supinator  longus,  extensor 
carpi  radialis  longior,  (the  extensor  carpi  radialis  bre- 
vier receiving  its  nerve  from  the  posterior  interosseous,) 
and  in  most  cases  the  brachialis  anticus. 

Fig.  365.  Plan  of  the  cutaneous  nerves  of  the  bark  of  the 
arm  and  fore-arm.  1.  Supra-acromia!  branches  of  the  cervical 
plexus.  2.  Cutaneous  branches  of  the  circumflex  nerve.  3. 

Internal  cutaneous  of  the  musculo-spiral.  4 Intercosio-humeral  branches.  5.  External  cutaneous 
(inferior)  o(  the  musculo-spiral.  6.  Ending  of  the  nerve  of  Wrisberg.  7.  Part  of  the  internal 
cutaneous  for  the  back  of  the  fore-arm.  8.  Offset  from  the  dorsal  branch  of  the  ulnar  nerve.  9. 
Radial  nerve.  10.  Branch  of  the  musculo-cutaneous  for  the  back  of  the  fore-arm. 


Fig.  365. 


Wa 


n;/ 


81G 


POSTERIOR  INTEROSSEOUS  NERVE. 


2.  External  cutaneom  branches. — These  are  two  in  number,  and  are  disposed  as 
follows : — 

The  vpper  branch,  the  smaller  of  the  two,  fig.  363,®,  is  directed  downwards  to 
the  fore  part  of  the  elbow,  along  the  cephalic  vein,  and  distributes  filaments  to 
the  lower  half  of  tire  upper  arm,  on  its  anterior  aspect.  The  lower  branch  extends 
as  far  as  the  wrist,  fig.  365,  distributing  olfsets  to  the  lower  half  of  the  arm,  and 
to  the  fore-arm,  on  their  posterior  aspect.  It  appears  beneath  the  integument  at 
the  outer  side  of  the  arm,  about  its  middle,  and  passes  to  the  fore-arm  over  the 
outer  side  of  the  bend  of  the  elbow.  About  the  middle  of  the  fore-arm  it  turns 
from  the  outer  to  the  posterior  aspect  of  the  limb,  and  is  connected  near  the  wrist 
with  a branch  of  the  external  cutaneous  nerve. 

Of  the  two  nerves  which  result  from  the  division  of  the  musculo- 
spiral,  one,  the  radial,  is  altogether  a cutaneous  nerve,  and  the  other 
(posterior  interosseous)  is  the  muscular  nerve  of  the  back  of  the 
fore-arm. 

A.  E.  A D I A L N E R V E. 

The  radial  nerve,  after  separating  from  the  musculo-spiral,  is  placed 
in  front  of  the  fore-arm,  close  to  its  outer  side,  and  afterwards  turning 
backwards,  is  distributed  to  the  integument  of  the  back  of  the  hand. 
At  first  it  is  concealed  by  the  long  supinator  muscle,  and  lies  a little 
to  the  outer  side  of  the  radial  artery.  This  position  beneath  the  supi- 
nator is  retained  to  about  three  inches  from  the  lower  end  of  the 
radius,  where  the  nerve  turns  outwards  beneath  the  tendon  of  that 
muscle,  and  becomes  subcutaneous.  Now  it  separates  into  two 
branches,  which  ramify  in  the  integument  over  the  dorsal  aspect  of 
the  thumb  and  the  next  two  fingers,  in  the  following  manner: 

Branches. — One  branch,  the  external  one,  extends  to  the  radial  side  of  the 
thumb,  and  is  joined  by  a branch  of  the  external  cutaneous  nerve.  It  distributes 
filaments  over  the  ball  of  the  thumb. 

The  internal  division  of  the  radial  nerve  communicates  with  a branch  of  the 
external  cutaneous  nerve  on  the  back  of  the  fore-arm,  and  on  the  hand  joins  in  an 
arch  with  the  dorsal  branch  of  the  ulnar  nerve.  It  then  divides  into  digital  nerves 
for  the  outer  fingers, — Dorsal  digital  nerves.  One  of  these  ramifies  on  the  ulnar 
side  of  the  thumb,  and  the  second  on  the  radial  side  of  the  index  finger.  The 
third  divides  between  the  opposed  sides  of  the  index  and  middle  fingers;  and  the 
fourth  between  the  middle  and  ring  fingers.  This  last  branch  is  connected  with 
a branch  of  the  ulnar  nerve.  On  the  .sides  of  the  fingers  the  posterior  digital 
nerves  now  described  join  offsets  sent  backwards  from  the  palmar  digital  nerves. 

B.  POSTERIOR  INTEROSSEOUS  NERVE. 

This  nerve,  the  larger  of  the  two  divisions  of  the  musculo-spiral 
nerve,  winds  to  the  back  of  the  fore-arm  through  the  fibres  of  the  supi- 
nator brevis  muscle,  and  is  prolonged  between  the  deep  and  superficial 
layers  of  the  extensor  muscles  to  the  interosseous  membrane,  which  it 
approaches  about  the  middle  of  the  fore-arm. 

Much  diminished  in  size  by  the  separation  of  numerous  branches 
for  the  muscles,  the  nerve  at  the  lower  part  of  the  fore-arm  lies  be- 
neath the  extensor  of  the  last  phalanx  of  the  thumb  and  the  tendons 
of  the  common  extensor  of  the  fingers,  and  terminates  on  the  bac.k  of 
the  carpus  in  a gangliform  enlargement.  From  this  body  filaments 
are  given  to  the  ligaments  and  articulations  on  which  it  rests. 

The  branches  of  the  interosseous  nerve  enter  the  surrounding  muscles,  viz.,  the 


UPPER  INTERCOSTAL  NERVES. 


317 


extensor  carpi  radialis  brevior  and  supinator  brevis,  the  superficial  layer  of  extensor 
muscles,  except  the  anconeus,  and  the  deep  layer  of  the  same  muscles ; — that  is 
to  say,  the  nerve  supplies  the  supinators  and  the  extensors  of  the  carpus  and  of 
the  fingers,  with  the  exception  of  the  supinator  longus  and  the  extensor  carpi 
radialis  longior. 

Summary  of  the  musCiilo-spiral  nerve. — The  trunk  of  the  nerve  sup- 
plies the  extensor  muscles  of  the  elbow-joint,  and  gives  a filament  to 
one  of  the  flexors  of  the  same  joint  (brachialis  anticus),  but  this  muscle 
receives  its  principal  nerves  from  another  source.  Before  dividing, 
the  nerve  likewise  gives  offsets  to  two  muscles  of  the  fore-arm  (the  long 
supinator,  and  the  long  radial  extensor  of  the  carpus).  The  posterior 
interosseous  division  distributes  nerves  to  the  remaining  muscles  on  the 
outer  and  back  part  of  the  fore-arm  (the  short  supinator  and  the  ex- 
tensors). 

Cutaneous  nerves  are  distributed,  from  the  trunk  of  the  nerve  and 
its  radial  division,  to  the  lower  part  of  the  upper  arm,  to  the  fore-arm, 
and  to  the  hand — on  the  posterior  and  outer  aspect  of  each. 

ANTERIOR  DIVISIONS  OF  THE  DORSAL  NERVES— 
INTERCOSTAL  NERVES. 

These  nerves,  fig.  367,  which  from  their  position  with  respect  to 
the  ribs  are  named  intercostal,  are  twelve  in  number,  and  are  distri- 
buted to  the  walls  of  the  thorax  and  abdomen.  The  connec,ting  cords 
with  the  sympathetic  nerve  are  placed  in  the  intercostal  spaces,  close 
to  the  vertebras. 

The  intercostal  nerves  pass  separately  .to  their  destination,  without 
forming  any  plexus  by  the  connexion  or  interlacement  of  their  fibres, 
and  in  this  respect  they  differ  from  the  other  spinal  nerves.  From  the 
intervertebral  foramina  they  are  directed  transversely  across  the 
trunk,  and  nearly  parallel  one  to  the  other.  The  upper  nerves,  with 
the  exception  of  the  first,  are  confined  to  the  parietes  of  the  thorax, 
while  the  lower  nerves  are  continued  from  the  intercostal  spaces  to 
the  muscles  and  integument  of  the  abdomen.  This  difference  in  dis- 
tribution constitutes  the  ground  of  the  division  of  the  intercostal  nerves 
into  two  sets,  between  which  the  nerves  are  divided  equally. 

THE  UPPER  INTERCOSTAL  NERVES. 

In  their  course  to  the  fore  part  of  the  chest,  these  nerves  accompany 
the  intercostal  blood-vessels.  After  a short  space  they  pass  between 
the  strata  of  the  intercostal  muscles,  and,  about  midway  between  the 
vertebrae  and  the  sternum,  give  off'  the  lateral  cutaneous  branches. 
The  nerves  are  now  continued  forwards,  amid  the  fibres  of  the  internal 
intercostal  muscles  as  far  as  the  costal  cartilages,  where  they  come 
into  contact  with  the  pleura.  In  approaching  the  sternum,  they  cross 
the  internal  mammary  artery  and  the  fibres  of  the  triangularis  sterni 
muscle.  Finally,  these  nerves  pierce  the  internal  intercostal  muscle 
and  the  greater  pectoral,  and  end  in  the  integument,  under  the  name 
of  the  anterior  cutaneous  nerves  of  the  thorax. 

Branches. — Besides  the  cutaneous  nerves  (two  sets)  already  indi- 
cated, many  branches  are  distributed  from  the  intercostal  nerves  to 
the  neighbouring  muscles.  The  several  offsets  require  separate  notice 

21* 


318 


FIRST  DORSAL  NERVE. 


Fig.  366. 


a.  The  lateral  cutaneous  nerves  of  the  thorax, 
fig.  366,  pierce  the  e.'^lernal  intercostal  and  ser- 
ratus  magnus  muscles  in  the  same  line,  a little 
behind  the  level  of  the  great  pectoral  muscle. 
Each  of  these  nerves,  except  that  from  the 
Second  intercostal,  (the  first  intercostal  nerve 
has  already  been  excluded  from  the  general 
account  of  these  nerves,)'  divides  into  two 
branches,  which  reach  the  integument  at  the 
same  time,  or  at  a short  distance  one  from  the 
other,  and  take  opposite  directions,  one  forward, 
the  other  backward,  and  hence  are  named  an- 
terior and  posterior. 

The  anterior  branches,  are  continued  for- 
wards to  where  the  cutaneous  nerves,  reflected 
outwards  from  the  fore  part  of  the  thorax,  end. 
Several  of  these  branches  reach  the  mammary 
gland  and  the  nipple ; and  from  the  lower  nerves 
offsets  are  supplied  to  the  digitations  of  the  ex- 
ternal oblique  muscle  of  the  abdomen. 

The  posterior  branches,  turn  backwards  to 
the  integument  over  the  scapula  and  the  latis- 
simus  dorsi  muscle.  That  derived  from  the 
second  intercostal  nerve  is  the  largest  of  these 
branches,  and  ends  in  the  skin  of  the  arm ; it 
will  be  presently  noticed  under  the  name  “ in- 
tercosto-humeral  nerve.”  The  branch  from  the 
third  nerve  ramifies  in  the  axillary  space,  and 
a few  filaments  likewise  reach  the  arm. 

b.  The  anterior  cutaneous  nerves  of  the  thorax,' 
(reflected  nerves,  — A.  Cooper,)  which  are 
the  terminal  twigs  of  the  intercostal  nerves,  are 
reflected  outwards  in  the  integument  over  the 
great  pectoral  muscle.  The  branch  from  the 
second  nerve  is  connected  with  the  supraclavi- 
cular and  the  lateral  cutaneous  merves ; those 
from  the  third  and  fourth  nerves  are  distributed 
to  the  mammary  gland. 

c.  Muscular  branches. — Numerous  filaments, 
which  are  usually  slender  and  of  various 
lengths,  are  supplied  to  the  intercostal  muscles, 
and  the  triangularis  sterni.  At  the  anterior  part 

of  the  chest,  some  of  these  branches  cross  the  cartilages  of  the  ribs,  passing  from 
one  intercostal  space  to  another. 


Plan  of  the  cutaneous  nerves  of  the 
chest  and  abdomen  (altered  from  a 
plate  of  M.  Bourgery).  a.  Section  of 
the  arm.  b.  Pectoral  muscle.  c. 
Latissimus  dorsi.  d.  E.xternal  ob- 
lique. e.  Serratus  magnus.  1,  ],  1. 
Anterior  cutaneous  nerves  of  the 
chest  and  belly.  2,  2,  2.  Anterior 
branches  of  the  lateral  cutaneous 
nerves  of  the  chest  and  belly.  3,  3,  3. 
Posterior  branchesofthesame.  4,4,  4. 
Cutaneous  branches  from  the  poste- 
rior divisions  of  the  lumbar  nerves. 
5.  Ilio-hypogastric.  6.  Small  occipital 
nerve. 


PECULIARITIES  OF  CERTAIN  DORSAL  NERVES. 


1.  First  Dorsal  Nerve. 

The  anterior  division  of  this  nerve  enters  almost  wholly  into  the 
brachial  plexus.  Usually  it  does  not  supply  a lateral  cutaneous 
branch  ; but  when  that  ordinarily  given  from  the  second  dorsal  nerve 
(intercosto-humeral  nerve)  is  wanting,  a branch  from  the  first  takes  its 
place.  Before  emerging  from  the  thorax  to  join  the  brachial  i lexus, 
this  nerve  gives  off  a small  intercostal  branch,  which  courses  along  the 
first  intercostal  space,  in  the 'manner  of  the  other  intercostal  nerves. 
From  this  branch  is  derived  the  first  of  the  anterior  cutaneous  nerves 
of  the  thorax.  The  cutaneous  nerve,  however,  is  wanting  in  some 
cases. 


LOWER  INTERCOSTAL  NERVES. 


319 


2.  Second  Intercostal  Nerve. 

The  second  intercostal  nerve  differs  from  the  rest,  chiefly  in  the 
size  of  its  lateral  cutaneous  branch.  This  branch  is  the  largest  of  the 
series  of  lateral  cutaneous  nerves.  It  commonly  wants  the  anterior 
division,  and  the  posterior  one  is  distributed  to  the  skin  of  the  arm, 
under  the  name  intercosto-humeral  nerve. 

The  intercosto-humeral  nerve,  proceeding  from  the  source  just  indicated,  crosses 
the  a.xillary  space  to  reach  the  arm,  and  is  connected  in  the  axilla  with  an  offset 
of  the  nerve  of  Wrisberg.  Now  penetrating  the  fascia,  it  becomes  subcutaneous, 
and  ramifies  in  the  integ-ument  of  the  upper  half  of  the  arm,  on  its  inner  and 
posterior  aspect,  fig.  365,  * \ a few  filaments  reach  the  integument  over  the 
scapula.  The  branches  o,f  this  nerve  cross  over  the  internal  cutaneous  offset  of 
the  musculo-spiral  nerve,  and.  a communication  is  established  between  the  two. 
— ^The  size  of  the  intercosto-humeral  nerve  (and  the  same  may  be  said  of  the 
extent  to  which  it  supplies  the  integument)  is  in  inverse  proportion  to  the  size 
of  the  other  cutaneous  nerves  of  the  upper  arm,  especially  the  nerve  of  Wrisberg 
(see  ante,  page  310). 

THE  LOWER  INTERCOSTAL  NERVES. 

The  lower  intercostal  nerves,  with  the  exception  of  the  last,  pass 
through  the  intercostal  spaces,  (fig.  367 ;)  and  in  this  part  of  their 
course  they  have  the  same  arrangement  as  the  nerves  of  the  upper 
series.  From  the  anterior  ends  of  the  intercostal  spaces,  they  are 
continued,  between  the  internal  oblique  and  the  transverse  muscle  of 
the  abdomen,  to  the  outer  edge  of  the  rectus.  Perforating  its  sheath, 
they  then  enter  the  substance  of  this  muscle,  and  terminate  in  small 
cutaneous  branches  (anterior  cutaneous). 

These  nerves  supply  the  intercostal  and 
abdo.minal  muscles,  and  they  are  con- 
nected one  with  another  between  the 
muscles  of  the  abdomen.  About  the  mid- 
dle of  their  course,  offsets  (lateral  cuta- 
neous nerves  of  the  abdomen)  are  trans- 
mitted to  the  integument  as  from  the 
upper  intercostal  nerves. 

a.  The  lateral  cutaneous  nerves  of  the 
abdomen,  fig.  366,  pass  to  the  Integument 
through  the  external  intercostal -and  ex- 
ternal oblique  muscles,  in  a line  with  the 
corresponding  nerves  on  the  thorax,  and 
divide  in  the  same  manner  into  anterior 
and  posterior  branches. 

The  anterior  branches  are  the  larger,  and  are 
directed  inwards  in  the  superficiaf  fascia,  with 
small  cutaneous  arteries,  nearly  to  the  edge  of 
the  rectus  muscle. 

The  posterior  branches  bend  backwards  over 

Fig.  367.  Plan  of  the  intercostal  nerves,  (altered  from 
Bourgery.)  a.  Cut  surface  of  the  arm.  b.  Pectoralis  minor 
muscle,  c.  Serratus  magnus  muscle.  3.  Subscapular 
muscle.  /.  Transverse  muscle  of  the  abdomen.  1,1,  1,1.  Anterior  ciitaneons  nerves  of  the 
thorax  and  abdomen.  2.  Posterior  thoracic  nerve.  3,  3,  3.  Intercostal  nerves.  4.  Lateral 
cutaneous  branch  of  the  last  dorsal  nerve. 


320 


LUMBAR  i\ERVES— ANTERIOR  DIVISIONS. 


the  latissimus  dorsi  muscle,  and  extend  towards  the  cutaneous  nerves  of  the 
back. 

b.  The  anterior  cutaneous  nerves*  of  the  abdomen  become  sub- 
cutaneous near  the  linea  alba,  with  small  perforating  arteries.  Their 
number  and  position  is  very  uncertain.  They  are  directed  outwards 
towards  the  lateral  cutaneous  nerves,  fig.  366. 

Last  Dorsal  Nerve. 

The  anterior  division  of  this  nerve  is  below  the  last  rib,  and  is  con- 
tained altogether  in  the  abdominal  wall.  The  nerve  has  the  general 
course  and  distribution  of  the  others,  between  the  internal  oblique  and 
transversalis,  but  before  taking  its  place  between  those  muscles,  it 
crosses  the  upper  part  of  the  quadratus  lumborum,  and  pierces  the 
aponeurosis  of  the  transverse  muscle  (lumbar  fascia).  This  nerve  is 
connected  by  offsets  with  the  nerve  above,  and  occasionally  with  the 
ilio-hypogastric  branch  of  the  lumbar  plexus.  Near  the  spine  it 
sometimes  communicates  with  the  first  lumbar  nerve  by  means  of  a 
small  cord  (dorsi-lumbar)  in  the  substance  of  the  quadratus  lum- 
borum. 

The  lateral  cutaneous  branch  of  the  last  dorsal  nerve  (fig.  367,  ‘‘,)  becomes  sub- 
cutaneous by  passing  through  both  oblique  muscles : it  is  then  directed  down- 
wards over  the  crest  of  the  ilium  to  the  integument  covering  the  fore  part  of  the 
gluteal  region  and  the  upper  and  outer  part  of  the  thigh,  some  filaments  reaching 
as  far  as  the  great  trochanter  of  the  femur. 

ANTERIOR  DIVISIONS  OF  THE  LUMBAR  NERVES. 

The  anterior  divisions  of  the  lumbar  nerves  increase  in  size  from 
the  first  to  the  fifth,  and  all,  except  the  fifth,  besides  giving  off  branches 
outwards,  are  connected  together  by  anastomotic  loops,  so  as  to  form 
the  lumbar  plexus.  On  leaving  the  intervertebral  foramina,  these 
nerves  are  connected  by  filaments  with  the  sympathetic  nerve,  and 
the  filaments  are  longer  than  those  connected  with  other  spinal  nerves, 
in  consequence  of  the  position  of  the  lumbar  sympathetic  ganglia, — 
on  the  fore  part  of  the  bodies  of  the  vertebrae.  In  the  same  situation 
small  twigs  are  furnished  to  the  psoas  and  quadratus  lumborum 
muscles. 

The  anterior  division  of  the  fifth  lumbar  nerve,  as  just  stated,  does 
not  enter  into  the  lumbar  plexus.  Having  received  a vertical  branch 
from  the  nerve  next  above  it,  it  descends  to  join  the  anterior  division 
of  the  first  sacral  nerve,  and  thus  forms  part  of  the  sacral  plexus. 
The  cord  resulting  from  the  union  of  a part  of  the  fourth  with  the  fifth 
nerve,  is  named  the  lumbosacral  nerve. 

Superior  Gluteal  Nerve. 

Before  joining  the  first  sacral  nerve,  the  1 umbo-sacral  cord  gives  off 
from  behind  the  superior  gluteal  nerve,  which  leaves  the  pelvis  through 
the  large  sacro-sciatic  foramen,  above  the  pyriformis  muscle,  and 
divides,  like  the  gluteal  artery,  into  two  branches,  which  are  distri- 
buted chiefly  to  the  smaller  gluteal  muscles. 

• A second  set  of  anterior  cutaneous  branches  is  described  by  Professor  Cruveilhier  as 
existing  at  the  outer  edge  of  the  rectus  muscle. 


LUMBAR  PLEXUS. 


321 


The  upper  branch  runs,  together  with  the  gluteal  artery,  along  the  origin  of  the 
gluteus  minimus,  and  is  lost  in  it,  and  in  the  gluteus  medius.  The  lower  branch 
crosses  over  the  middle  of  the  gluteus  minimus,  between  it  and  the  gluteus  me- 
dius, and  having  supplied  filaments  to  both  these  muscles,  is  continued  forwards, 
and  terminates  in  the  tensor  muscle  of  the  fascia  lata. 


LUMBAR  PLEXUS. 


Fig.  368. 


The  lumbar  plexus  is  formed 
by  the  connexion  of  the  ante- 
rior divisions  of  the  four  upper 
lumbar  nerves.  It  is  placed 
in  the  substance  of  the  psoas 
muscle,  in  front  of  the  trans- 
verse processes  of  the  corre- 
sponding vertebree.  Above,  the 
plexus  is  narrow,  and  is  some- 
times connected  with  the  last 
dorsal  nerve  by  a small  fila- 
ment named  dorsi-lumbar ; be- 
low it  is  wider,  and  is  joined 
to  the  sacral  plexus  by  means 
of  the  lumbo-sacral  nerve. 

The  arrangement  of  the  nerves 
constituting  the  plexus,  and  the 
iriode  of  origin  of  its  several 
branches,  may  be  thus  stated : — 

The  first  nerve  gives  off  the  ilio- 
hypogastric and  ilio-inguinal  nerves, 
and  sends  downwards  a communi- 
cating branch  to  the  second  nerve. 

The  second  furnishes  the  genito- 
cmral  and  external  cutaneous 
nerves,  and  gives  a connecting 
branch  to  the  third  nerve.  From 
the  third  nerve,  besides  the  de- 
scending branch  to  the  fourth,  two  ^he  lumbar  plexus  and  its  branches  (slightly  al- 

A lered  from  Schmidt),  a.  Last  rib.  b.  Quadratus  lum- 

r ches  proceed,  one  of  which,  ^luscle.  c.  Oblique  and  transverse  muscles, 

the  larger,  forms  part  of  the  ante-  cut  near  the  crest  of  the  ilium,  d.  Os  pubis,  e.  Ad- 
rior  crural  nerve  J the  other,  a part  duclor  brevis  muscle.  /.  Pectineus.  g.  Adductor 
of  the  obturator  nerve.  The  fourth  >ongus.  1.  Ilio-hypogastric  branch.  2.  Ilio-inguinal. 
nerve  sends  two  branches,  which  3-  External  cutaneous  branch.  4.  Anterior  crural 

. w xT_  1 .c  ’.c  1 nerve.  5.  Accessory  obturator.  6 Obturator  nerve. 

sen  e to  complete  the  obturator  and  7 Genito-crural  nerve  divided  into  two  at  its  origin 
anterior  crural  nerves,  and  a con-  from  the  plexus.  8.  Gangliated  cord  of  the  sympa- 
necting  branch  to  the  fifth  nerve,  thetic  nerve. 

The  fifth,  with  the  connecting 

branch  just  mentioned,  is  the  lumbo-sacral  nerve  already  described. 

The  hranclies  of  this  plexus  form  two  sets,  which  are  distributed, 
one  to  the  lower  part  of  the  wall  of  the  abdomen,  the  other  to  the  fore 
part  and  inner  side  of  the  lower  limb.  Among  the  former  set  are  the 
ilio-hypogastric  and  the  ilio-inguinal  nerve,  and  part  of  the  genito- 
crural;  and  to  the  latter  belong  the  remaining  part  of  the  genito-crura! 
nerve,  the  external  cutaneous,  the  obturator,  and  the  anterior  crural 
nerves. 


322 


ILIO-INGUINAL  NERVE. 


Ilio-hypogastric  and  Ilio-inguinal  Nerves. 

The  two  upper  branches  from  the  lumbar  plexus,  viz. — the  ilio- 
hypogastric and  ilio-inguinal  (superior  and  middle  musculo-cutaneus, 
— Bichat),  are  both  derived  from  the  first  lumbar  nerve,  and  are  des- 
tined to  supply  nearly  similar  parts.  They  become  subcutaneous  by 
passing  between  and  then  through  the  broad  muscles  of  the  abdomen, 
and  end  in  the  integument  of  the  groin  and  scrotum  (or  labia  pu- 
dendi),  as  well  as  in  that  covering  the  gluteal  muscles.  In  the  relative 
size  of  these  two  nerves,  a principle  of  compensation  is  observed  to 
exist, — the  extent  of  distribution  of  the  one  being  inversely  to  the  ex- 
tent of  the  other. 

A.  The  ilio-hypogastric  nerve,  fig.  368,%  passes  from  within  the 
cavity  of  the  abdomen  to  its  walls,  in  which  it  is  placed  at  first  be- 
tween the  muscles,  and  ends  beneath  the.  skin.  Emerging  from  the 
upper  part  of  the  psoas  muscle  at  its  outer  border,  it  runs  obliquely 
over  tbe  quadratus  lumborum  to  the  crest  of  the  ilium  ; and  there  per- 
forating the  transverse  muscle  of  the  abdomen,  gets  between  that  mus- 
cle and  the  internal  oblique,  and  divides  into  an  iliac  and  a hypogastric 
branch. 

a.  The  iliac  branch  pierces  the  attachment  of  both  oblique  muscles,  imme- 
diately above  the  upper  border  of  the  ilium,  and  is  lost  in  the  integument  over 
the  gluteal  muscles, — behind  the  part  supplied  by  the  lateral  cutaneous  branch 
of  the  last  dorsal  nerve. 

b.  The  hypogastric  or  abdominal  branch,  continues  on  between  the  transverse 
and  internal  oblique  muscles,  and  is  connected  with  the  ilio-inguinal  nerve  near 
the  crest  of  the  ilium.  It  then  perforates  in  succession  both  the  oblique  muscles, 
passing  through  the  external  oblique  near  the  pubes,  and  not  far  from  the  middle 
line.  Having  become  subcutaneous,  this  branch  is  distributed  to  the  skin  over 
the  hypogastric  region,  fig.  370,'. 

The  size  of  the  iliac  branch  of  this  nerve  varies  according  to  that  of  the  lateral 
cutaneous  branch  of  the  twelfth  dorsal.  The  hypogastric  branch  is  not  unfre- 
quently  joined  with  the  last  dorsal  nerve  between  the  muscles,  and  near  the  crest 
of  the  ilium. 

B.  The  ilio-inguinal  nerve,  368,=  (inferior  musculo-cutaneoiis, 
— Bichat),  smaller  than  the  preceding,  with  which  it  has  a common 
origin  from  the  first  lumbar  nerve,  supplies  the  integument  of  the  groin. 
It  descends  obliquely  outwards  over  the  quadratus  lumborum,  and  then 
over  the  iliacus  muscle.  In  this  part  of  its  course,  the  nerve  is  placed 
lower  down  than  the  ilio-hypogastric ; and  having  perforated  the 
transverse  muscle,  further  forward  than  that  nerve,  communicates  with 
it  between  the  abdominal  muscles,  near  the  anterior  end  of  the  crest  of 
the  ilium.  Passing  through  the  fleshy  part  of  the  internal  oblique  mus- 
cle, and  afterwards  through  the  external  abdominal  ring,  the  ilio-ingui- 
nal  nerve  becomes  subcutaneous,  fig.  370,%  and  is  distributed  to  the 
skin  upon  the  groin,  as  well  as  to  that  upon  the  scrotum  in  the  male,  or 
the  labium  pudendi  in  the  female.  In  its  progress  this  nerve  furnishes 
branches  to  the  internal  oblique  muscle. 

The  ilio-inguinal  nerve  occasionally  arises  from  the  loop  connecting  the  first 
and  second  lumbar  nerves.  It  is  sometimes  small,  and  ends  near  the  ere  h of 
the  ilium  by  joining  the  ilio-jiypogastric  nerve,  which  in  that  case  gives  of(  an 
inguinal  branch,  having  a similar  course  and  distribution  to  the  ilio-inguinal 
nerve,  the  place  of  which  it  supplies. 


EXTERNAL  CUTANEOUS  NERVE. 


323 


Genito-crural  Nerve. 

The  genito-crural  nerve  (Bichat),  fig.  368, ^ as  its  name  implies, 
belongs  partly  to  the  external  genital  organs  and  partly  to  the  thigh. 
It  is  derived  chiefly  from  the  second  lumbar  nerve,  but  also  receives  a 
few  fibres  from  the  connecting  cord  between  that  nerve  and  the  first. 
The  nerve  descends  obliquely  through  and  afterwards  on  the  fore  part 
of  the  psoas  muscle  towards  Poupart’s  ligament,  dividing  at  a variable 
height  into  an  internal  or  genital,  and  an  externa]  or  crural  branch.* 

a.  The  genital  branch  lies  upon  or  near  the  external  iliac  artery,  and  sends 
filaments  on  that  vessel ; then  perforating  the  transversalis  fascia,  it  passes  through 
the'  inguinal  canal  with  the  spermatic  cord,  upon  which  it  communicates  with 
the  inferior  pudendal  nerve,  and  is  then  lost  upon  the  cremaster  muscle.  In  the 
female  it  accompanies  the  round  ligament  of  the  uterus,  and  is  distributed  to  the 
labium  pudendi. 

b.  The  crural  branch  descends  upon  the'psoas  muscle  beneath  Poupart’s  liga- 
ment into  the  thigh.  Immediately  below  that  ligament,  and  at  the  outer  side  of 
the  femoral  artery,  it  pierces  the  fascia  lata,  fig.  370,^ ; and,  having  become  sub- 
cutaneous, supplies  the  skin  on  the  upper  part  of  the  thigh,  and  communicates 
with  the  middle  cutaneous  branch  of  the  anterior  crural  nerve.  'Whilst  passing 
beneath  Poupart’s  ligament,  some  filaments  are  prolonged  from  this  nerve  on  to 
the  femoral  artery .f 

External  Cutaneous  Nerve. 

This  nerve,  fig.  368,®,  descends  through  the  lower  part  of  the  abdo- 
men, and  ends  in  the  integument  upon  the  outer  side  of  the  thigh. 

Commencing  from  the  loop  formed  between  the  second  and  third 
lumbar  nerves,  it  reaches  the  surface  of  the  psoas  muscle  about  the 
middle  of  its  outer  border.  Thence  it  is  directed  across  the  iliacus 
muscle  to  the  notch  beneath  the  anterior  superior  spine  of  the  ilium, 
where  it  escapes  from  the  abdomen.  Whilst  passing  beneath  Poupart’s 
ligament  to  enter  the  thigh,  it  divides  into  two  branches  of  nearly 
equal  size: — 

a.  One,  the  posterior  branch,  perforates  the  fascia  lata,  and  subdivides  into  two 
or  three  others,  which  turn  backwards  and  supply  the  skin  upon  the  outer  surface 
of  the  limb,  from  the  upper  border  of  the  ilium  nearly  to  the  middle  of  the  thigh; 
the  highest  among  the  branches  are  crossed  by  the  cutaneous  branches  from  the 
last  dorsal  nerve. 

b.  The  second,  or  anterior  branch  of  the  external  cutaneous  nerve,  is  at  first 
contained  in  a sheath  or  canal  formed  in  the  substance  of  the  fascia  lata ; but, 
about  four  inches  below  Poupart’s  ligament,  it  enters  the  subcutaneous  cellular 
tissue,  and  descends  beneath  the  skin  along  the  outer  part  of  the  front  of  the 
thigh,  giving  off  branches  in  its  course,  and  ending  near  the  knee.  The  prmcipal 
offsets  are  those  springing  from  its  outer  side. 

The  two  branches  of  the  external  cutaneous  nerve  communicate  one  with  the 
other  at  the  upper  part  of  the  thigh ; and,  in  some  cases,  the  anterior  branch 
reaches  quite  down  to  the  knee,  and  communicates  there  with  the  long  saphenous 
nerve. 

* This  nerve  often  bifurcates  close  to  its  origin  from  the  plexus,  in  which  case  its  two 
branches  perforate  the  psoas  muscle  in  different  places.  Schmidt  describes  them  as  sepa- 
rate  nerves,  naming  the  genital  branch,  the  external  spermatic,  and  the  crural  branch, 
lumbo-inguinal. 

+ It  is  stated  by  Schmidt,  that  when  the  crural  branch  of  the  genito-crural  nerve  is 
large,  and  commences  high  up  near  the  plexus,  he  has  observed  it  to  give  off  a muscular 
branch,  which  was  distributed  to  the  lower  border  of  the  internal  oblique  and  transversalis 
muscles. 


324 


OBTURATOR  NERVE— BRANCHES. 


OBTURATOR  NERVE. 

The  obturator  nerve  (internal  crural),  fig.  308,'*,  is  distributed  to 
the  adductor  muscles  of  the  thigh,  and  to  the  hip  and  knee-joints. 

This  nerve  arises  from  the  lumbar  plexus  by  two  cords  or  roots, 
one  proceeding  from  the  third  and  the  other  from  the  fourth  lumbar 
nerve.  Having  emerged  from  the  inner  border  of  the  psoas  muscle, 
opposite  to  the  brim  of  the  pelvis,  it  runs  along  the  side  of  the  pelvic 
cavity  above  the  obturator  vessels,  as  far  as  the  opening  in  the 
upper  part  of  the  thyroid  foramen,  through  which  it  escapes  from  the 
pelvis  into  the  thigh.  Here  it  immediately  divides  into  an  anterior 
and  a posterior  branch,  which  are  separated  one  from  the  other  by 
the  short  adductor  muscle. 

The  anterior  division,  placed  in  front  of  the  adductor  brevis  and 
behind  the  pectineus  and  adductor  longus  muscles,  gives  some  mus- 
cular ofl'sets,  and  then  inclines  downwards  to  the  middle  of  the  thigh, 
at  its  inner  side,  where, — at  the  lower  border  of  the  adductor  longus 
and  still  beneath  the  fascia — it  communicates  by  an  offset  with  the 
internal  cutaneous  branch  of  the  anterior  crural  nerve,  and  with  a 
branch  of  the  long  saphenous  nerve,  forming  a sort  of  plexus.  This 
branch  of  the  nerve  then  turns  outwards  upon  the  femoral  artery,  and 
surrounds  that  vessel  with  small  filaments. 

Branches. — Near  the  thyroid  membrane,  the  anterior  division  of  the  obturator 
nerve  gives  off  an  articular  branch  to  the  hip-joint.  Beneath  the  pectineus  mus- 
cle, it  receives  a communicating  branch  from  the  accessory  nerve  to  the  obturator, 
when  that  nerve  exists;  and  in  the  same  situation  supplies  branches  to  the  gra- 
cilis and  adductor  longus  muscles,  and  occasional!}'  also  others  to  the  adductor 
brevis  and  pectineus. 

Occasional  cvlaneom  nerve. — In  some  instances  the  communicating  offset  above 
described  is  larger  than  usual, .and  is  prolonged' downwards  as  a cutaneous  nerve 
to  the  thigh  and  leg.  When  thus  enlarged  the  branch  referred  to,  after  escaping 
below  the  border  of  the  long  adductor  muscle,  descends  along  the  posterior  bor- 
der of  the  sartorius  to  the  inner  side  of  the  knee.  Here  it  perforates  the  fascia, 
communicates  with  the  long  saphenous  nerve,  and  extends  down  the  inner  side 
of  the  limb,  supplying  the  skin  as  low  as  the  middle  of  the  leg. 

When  this  cutaneous  branch  of  the  obturator  nerve  is  present,  the  internal  cu- 
taneous branch  of  the  anterior  crural  nerve  is  small,  the  size  of  the  two  nervfes 
bearing  an  inverse  proportion  one  to  the  other. 

The  posterior  or  deep  division  of  the  obturator  nerve,  having  passed 
through  some  fibres  of  the  external  obturatdr  muscle,  crosses  behind 
the  short  adductor  to  the  fore  part  of  the  adductor  magnus,  where  it 
divides  into  many  branches,  all  of  which  enter  the  muscles,  excepting 
one  which  is  prolonged  downwards  to  the  knee-joint. 

Branches. — The  muscular  branches  supply  the  external  obturator  and  the  great 
adductor  muscle,  with  also  the  short  adductor,  when  that  muscle  receives  no 
offset  from  the  anterior  division  of  the  nerve. 

The  articular  branch  (for  the  knee)  rests  at  first  on  the  adductor  magnus,  but 
perforates  the  lower  fibres  of  that  muscle,  and  thus  reaches  the  upper  part  of  the 
popliteal  space.  Supported  by  the  popliteal  artery,  and  sending  filaments  around 
that  vessel,  the  nerve  then  descends  to  the  back  of  the  knee-joint,  and  enters  the 
articulation  through  the  posterior  ligament.* 


See  a paper  by  Dr.  A.  Thomson,  London  Med.  and  Surg-.  Journal,  No.  xcv. 


ANTERIOR  CRURAL  NERVE— BRANCHES. 


325 


Accessory  Obturator  Nerve. 

The  accessory  obturator  iierve  (nervus  ad  obturatorem 
accessorius,  inconstans — Schmidt),  a small  and  incon- 
stant nerve,*  communicates  with  the  obturator  nerve  in 
the  thigh,  and  is  distributed  to  the  hip-joint,  fig.  368,^. 

Arising  from  the  obturator  nerve  near  its  upper  end, 
or  from  the  third  and  fourth  lumbar  nerves,  this  acces- 
sory nerve  descends  beneath  the  fascia  along  the  inner 
border  of  the  psoas  muscle,  as  far  as  the  body  of  the 
pubes,  beyond  which  it  gets  behind  the  pectineus  mus- 
cle, and  ends  by  dividing  into  several  branches.  Of 
these  one  joins  the  anterior  branch  of  the  obturator 
nerve ; another  penetrates  the  pectineus  on  its  under 
surface;  whilst  a third  enters  the  hip-joint  ypith  the 
articular  artery. 

This  nerve  is  sometimes  small,  and  ends  in  filaments 
which  lie  upon  and  perforate  the  fibrous  capsule  of  the 
hip-joint,  when  it  is  altogether  wanting,  the  hip-joint 
receives  branches  from  the  obturator  nerve  itself. 

Summary. — The  obturator  nerve  and  its  ac- 
cessory give  branches  to  the  hip  and  knee-joints, 
also  to  the  adductor  muscles  of  the  thigh,  and, 
in  some  cases,  to  the  pectineus.  Occasionally 
a cutaneous  branch  descends  to  the  inner  side 
of  the  thigh,  and  to  the  inner  and  upper  part  of 
the  leg. 

ANTERIOR  CRURAL  NERVE. 

This  nerve,  fig.  368,“  supplies  the  muscles 
which  extend  the  leg,  and  sends  cutaneous 
branches  to  the  fore  part  of  the  thigh  and  the 
inner  side  of  the  leg. 

It  is  the  largest  branch  of  the  lumbar  plexus, 
and  is  derived  in  part  from  the  second,  but 
principally  from  the  third  and  fourth  lumbar 
nerves.  Situated  at  first,  like  the  other  branches 
of  this  plexus,  among  the  fibres  of  the  psoas,  it 
emerges  from  the  outer  border  of  that  muscle 
near  its  lower  part,  and  is  then  lodged  betw'een 
the  psoas  and  iliacus  muscles,  in  which  position 
it  descends  beneath  Poupart’s  ligament  into  the 
thigh. 

On  the  thigh,  fig.  369,  the  anterior  crural 
nerve  is  placed  deeply  between  the  psoas  and 
iliacus  muscles,  about  half  an  inch  to  the  outer 
side  of  the  femoral  artery,  and  soon  becoming 

Fig.  369.  Plan  of  nerves  given  from  the  lumbar  plexus  to  the 
lower  limb.  1.  External  cutaneous  nerve.  2,3.  Branches  of  the 
same.  4.  Anterior  crural  nerve.  5,  6.  Middle  cutaneous.  7. 
Internal  cutaneous  (anterior  portion).  8.  Long  saphenous  nerve. 
9,  10.  Muscular  branches.  12.  Cutaneous  branch  of  the  musculo- 
cutaneous nerve  of  the  leg  13.  Anterior  tibial. 


Fig.  369. 


* Schmidt  states  that  he  found  this  nerve  “ four  or  five  times  in  nine  or  ten  bodies.” 

Cominentar.  de  Nervis  lumbalibus,”  § xl. 


VOL.  II. 


28 


326 


INTERNAL  CUTANEOUS  NERVE. 


flattened  out,  divides  into  two  parts,  of  which  one  is  anterior  and  fur- 
nishes  cutaneous  branches,  while  the  other  (the  posterior,  or  deep 
part),  is  distributed  to  muscles.  In  some  cases,  it  is  found  to  divide 
into  four  instead  of  two  parts. 

Branches. — The  branches  given  from  the  anterior  crural  nerve 
within  the  abdomen  are  few  and  of  small  size.  Some  supply  the  iliacus 
muscle,  and  one  ramifies  over  the  femoral  artery. 

The  iliacus  receives  three  or  four  small  branches,  which  are  directed  outwards 
from  the  nerve  to  the  fore  part  of  the  muscle. 

The  nerve  of  the  femoral  artery  (nerv.  arteri®  crurali  proprius, — Schmidt),  divides 
into  numerous  filaments  upon  the  upper  part  of  that  vessel.— This  small  branch 
varies  somewhat  in  its  origin.  It  sometimes  arises  lower  down  than  usual  in 
the  thigh ; it  may,  on  the  other  hand,  be  found  to  take  origin  above  the  ordinary 
position,  and  in  this  case  it  proceeds  from  the  middle  cutaneous  nerve  when 
that  branch  springs  from  or  near  the  lumbar  plexus.  In  either  case,  its  ultimate 
distribution  is  the  same  as  that  already  described. 

From  the"'principal  or  terminal  divisions  of  ihe  nerve  the  remaining 
branches  take  their  rise  as  follows : — 

A.  From  the  anterior  division,  cutaneous  branches  are  given  to  the 
fore  part  of  the  thigh,  and  to  the  inner  side  of  the  leg.  They  are  the 
middle  and  internal  cutaneous  nerves  and  the  long  saphenous  nerve. 
One  of  the  muscles  (the  sartorius)  receives  its  nerves  from  this  series. 

Middle  Cutaneous  Nerve. 

The  middle  cutaneous  nerve,  fig.  370,  pierces 
the  fascia  lata  about  three  inches  below  Pou- 
part’s  ligament, ' and  soon  divides  into  two 
branches,'*  which  descend  side  by  side  beneath 
the  integument  on  the,  fore  part  of  the  thigh  to 
the  inner  side  and  front  of  the  patella.  These 
two  branches  give  off  on  each  side  numerous 
offsets  to  the  skin.  After  the  nerve  has  become 
subcutaneous,  it  communicates  with  the  crural 
branch  of  the  genito-cruraJ  nerve,  and  also  with 
the  succeeding  nerve,  the  internal  cutaneous. 

This  nerve  sometimes  arises  from  the  anterior  crural, 
high  up.  within  the  abdomen. 

Internal  Cutaneous  Nerve. 

The  internal  cutaneous  nerve,  fig.  370,^  gives 
branches  to  the  skin  on  the  inner  side  of  the 
thigh,  and  the  upper  part  of  the  leg ; but  the 
extent  to  which  it  reaches  depends  upon  the  pre- 
sence of  the  “ occasional  cutaneous”  branch  of 
the  obturator  nerve. 

This  nerve,  lying  beneath  the  fascia  lata,  de- 

Fig.  370.  Plan  of  the  cutaneous  nerves  on  the  front  of  the  thigh. 
1.  llio-hypog.aslric  branch.  2.  llio-inguinal  branch.  3,3.  Branches ul 
external  cutaneous  nerve.  4.  Branches  of  middle  cnianeous  nerve. 
5.  5.  Internal  cutaneous:  the  lower  number  refers  to  the  anterior 
division  of  this  nprve.  6.  Long  saphenous  nerve,  when  become 
subcutaneous.  7.  Crural  branch  of  the  genito-crural  nerve. 


Fig.  370. 


LONG  SAPHENOUS  NERVE— BRANCHES. 


327 


scends  obliquely  over  the  upper  part  of  the  femoral  artery.  It  divides 
either  in  front  of  that  vessel,  or  at  its  inner  side,  into  two  branches, 
(one  anterior,  the  other  internal,)  which  pierce  the  fascia  separately. 
These  two  branches  sometimes  arise  as  distinct  offsets  from  the  ante- 
rior division  of  the  anterior  crural  nerve. 

Branches  of  the  internal  cutaneous  nerve. — Previously  to  dividing  into  its  tvro  ulti- 
mate branches,  this  nerve  gives  off  two  or  three  cutaneous  twigs,  which  accom- 
pany the  upper  part  of  the  long  saphenous  vein.  The  highest  of  these  perforates 
the  fascia  near  the  saphenous  opening,  and  reaches  down  to  the  middle  of  the 
thigh.  The  others  appear  beneath  the  skin  lower  down  by  the  side  of  the  vein; 
one,  larger  than  the  rest,  passes  through  the  fascia  about  the  middle  of  the  thigh, 
and  extends  to  the  knee. — In  some  instances,  these  small  offsets  spring  directly 
from  the  anterior  crural  nerve,  and  they  often  communicate  with  each  other. 

The  two  terminal  branches  of  the  nerve  are  disposed  as  follows. 

a.  The  anterior  branch f descending  in  a straight  line  to  the  knee,  perforates  the 
fascia  lata  in  the  lower  part  of  the  thigh,  and  afterwards  runs  down  near  the  inter- 
muscular septum,  giving  off  filaments  on  each  side  to  the  skin.  Finally,  it  is 
directed  over  the  patella  to  the  outer  side  of  the  knee,  communicating,  as  it 
crosses  above  the  joint,  with  a branch  of  the  long  saphenous  nerve.  Very  often, 
however,  it  receives  only  a small  filament  from  the  saphenous  nerve,  and  then 
takes  the  place  of  the  branch  usually  given  by  the  latter  to  the  integument  over 
the  patella. 

This  branch  of  the  internal  cutaneous  nerve  sometimes  lies  above  the  fascia  in 
its  whole  length.  It  occasionally  gives  off  a cutaneous  filament,  which  accom- 
panies the  long  saphenous  vein,  and  in  some  cases  it  communicates  with  the 
branch  to  be  ne.xt  described. 

h.  The  inner  branch  of  the  internal  cutaneous  nerve  descends  along  the  posterior 
border  of  the  sartorius  muscle  to  the  inner  side  of  the  knee,  fig.  372, ‘ where  it 
perforates  the  fascia  lata,  and  communicates  by  a small  branch  with  the  long 
saphenous  nerve,  which  here  descends  in  front  of  it.  Having  given  off  some 
cutaneous  filaments  to  the  lower  part  of  the  thigh  on  its  inner  side,  the  nerve  is  then 
continued  downwards  to  be  distributed  to  the  skin  upon  the  inner  side  of  the  leg. 

Whilst  beneath  the  fascia,  this  branch  of  the  internal  cutaneous  nerve  joins  in 
an  interlacement,  on  the  inner  side  of  the  thigh,  with  branches  of  the  obturator 
and  saphenous  nerves. — Where  the  communicating  branch  of  the  obturator  nerve, 
just  referred  to,  is  of  large  size,  and  is  continued  to  the  skin  of  the  leg,  the  inter- 
nal cutaneous  nerve  does  not  reach  beyond  the  interlacement  of  nerves  in  which 
it  has  been  stated  to  take  part ; occasionally,  however,  a few  filaments  are  found 
to  reach  as  far  as  the  knee. 

Long  Saphenous  Nerve. 

The  long  or  interna]  saphenous  nerve,  fig.  369,®,  which  supplies  in 
part  the  skin  upon  the  thigh  and  leg,  is  the  largest  of  the  cutaneous 
branches  of  the  anterior  crural  nerve.  In  some  cases  it  arises  in 
connexion  with  one  of  the  deep  or  muscular  branches. 

This  nerve  is  deeply  placed  as  far  as  the  knee,  and,  in  the  rest  of 
its  course,  is  subcutaneous.  In  the  thigh  it  accompanies  the  femoral 
vessels,  lying  at  first  somewhat  to  their  outer  side,  but  lower  down 
approaching  close  to  them,  and  passing  beneath  the  same  aponeurosis. 
When  the  vessels  pass  through  the  opening  in  the  adductor  muscle 
into  the  popliteal  space,  the  long  saphenous  nerve  separates  from  them, 
and  is  continued  downwards  beneath  the  sartorius  muscle  to  the  inner 
side  of  the  knee  ; where,  having  first  given  off  as  it  lies  upon  the  inner 
condyle  of  the  femur  a branch  which  is  distributed  over  the  front  of 
the  patella,  it  becomes  subcutaneous  by  piercing  the  fascia  between 
the  tendons  of  the  sartorius  and  gracilis  muscles. 


328 


ANTERIOR  CRURAL  NERVE-MUSCULAR  BRANCHES. 


Having  become  subcutaneous,  the  nerve  then  accompanies  the  long 
saphenous  vein  along  the  inner  side  of  the  leg  down  to  the  foot,  fig. 
373,  \ The  position  it  bears  with  regard  to  the  vein  is  liable  to  vari- 
ation. It  may  be  described  as  descending  behind  the  inner  border  of 
the  tibia,  and,  about  the  lower  third  of  the  leg,  dividing  into  two 
branches.  One  of  these  follows  the  margin  of  the  tibia,  and  termi- 
nates near  the  inner  ankle  ; whilst  the  other  and  larger  branch  accom- 
panies the  vein  in  front  of  the  ankle,  and  ends  in  the  integument  on 
the  inner  side  of  the  foot.  Some  filaments  are  found  to  enter  the 
tarsal  ligaments. 

Branches. — a.  About  the  middle  of  the  thigh,  the  long  saphenous  nerve  gives 
off  a commmiicatmg  branch  to  join  in  the  interlacement  already  noticed  as  formed 
beneath  the  fascia  lata  by  this  nerve  and  branches  of  the  obturator  and  internal 
cutaneous  nerves.  After  it  has  left  the  aponeurotic  covenng  of  the  femoral  ves- 
sels, the  long  saphenous  nerve  has,  in  some  cases,  a further  connexion  with  one 
or  other  of  the  nerves  just  referred  to.  . 

b.  The  branch  given  to  the  integument  in  front  ofthepatella  perforates  the  sartorius 
muscle  and  the  fascia  lata ; and.  Raving  received  a communicating  offset  from  the 
internal  cutaneous  nerve,  divides  into  many  filaments,  which  spread  out  upon  the 
fore  part  of  the  knee.  Some  of  these  descend,  and  are  connected  with  other 
branches  of  the  long  saphenous  nerve  below  the  knee  ; others  turn  outwards,  and, 
by  uniting  with  branches  of  the  middle  and  external  cutaneous  nerves,  form  a 
plexus  (plexus  patellre). 

In  some  bodies,  the  last-described  branch  is  very  small,  and  ends  by  joining 
the  internal  cutaneous  nerve,  which,  in  that  case,  supplies  its  place  on  the  front 
of  the  knee-joint. 

Besides  the  communications  already  mentioned,  the  long  saphenous  nerve  is 
connected  in  the  leg  wdth  the  cutaneous  branch,  derived  either  from  the  internal 
cutaneous  or  obturator  nerve. 

B.  The  DEEP  SERIES  of  the  branches  of  the  anterior  crural  nerve 
supply  the  muscles  situated  on  the  fore  part  of  the  thigh,  and  also  one 
of  those  on  the  inner  side,  viz.,  the  pectineus.  They  may  be  thus 
described. 

Muscular  Branches. 

The  branch  to  the  pectineus  muscle  (which  sometimes  forms  one  of  the  anterior 
series)  crosses  inwards  behind  the  femoral  vessels,  and  enters  the  muscle  on  its 
anterior  aspect. 

The  sartorius  muscle  receives  three  or  four  branches,  which  arise  in  common 
with  the  cutaneous  nerves,  and  mostly  reach  the  upper  part  of  the  muscle. 

The  rectus  muscle  receives  a distinct  branch  on  its  under  surface. 

The  nerve  for  the  vastus  externus,  of  considerable  size,  descends  with  the 
branches  of  the  external  circumflex  artery,  towards  the  lower  part  of  the  muscle. 
It  gives  off  a long  slender  articular  filament,  which  reaches  the  knee,  and  pene- 
trates the  fibrous  capsule  of  the  joint. 

Another  large  branch  divides  into  two  sets,  which  enter  the  vastus  internus  and 
the  crureus  about  the  middle  of  those  muscles.  The  nerve  of  the  vastus  internus 
(sometimes  inaptly  named  the  short  saphenous  nerve),  before  penetrating  the 
muscular  fasciculi,  gives  a small  offset  to  the  knee-joint.  This  articular  nerve 
passes  along  the  internal  intermuscular  septum,  with  a branch  of  the  anastomotic 
artery,  as  far  as  the  inner  side  of  the  joint,  where  it  perforates  the  capsular  liga- 
ment, and  is  directed  outwards  on  the  synovial  membrane  beneath  the  ligamentura 
patelliB. 

Summary. — The  anterior  crural  nerve  is  distributed  to  the  skin  upon 
the  fore  part  and  inner  side  of  the  thigh,  commencing  below  the 


SACRAL  NERVES— ANTERIOR  DIVISIONS. 


329 


terminations  of  the  ilio-inguinal  and  genito-crural  nerves.  It  also 
furnishes  a cutaneous  nerve  to  the  inner  side  of  the  leg  and  foot. 

All  the  muscles  on  the  front  and  outer  side  of  the  thigh  receive 
their  nerves  from  the  anterior  crural,  and  one  of  the  muscles  on  the 
inner  side  of  the  limb  (the  pectineus)  is  also  in  part  supplied  by  this 
nerve.  The  tensor  muscle  of  the  fascia  lata  is  supplied  from  a dif- 
ferent source,  viz.,  the  superior  gluteal  nerve. 

Lastly,  two  branches  are  given  from  the  same  nerve  to  the  knee- 
joint. 

ANTERIOR  DIVISIONS  OF  THE  SACRAL  AND  COCCYGEAL  NERVES. 

Sacral  nerves. — The  anterior  divisions  of  the  first  four  of  these 
nerves  emerge  through  the  anterior  sacral  foramina,  and  the  fifth 
escapes  with  the  coccygeal  nerve  from  the  sacral  canal  at  its  end. 

The  first  two  of  the  sacral  nerves  are  of  large  and  about  equal  size, 
the  others  diminish  rapidly,  and  the  fifth  is  exceedingly  slender.  Like 
the  corresponding  divisions  of  all  the  other  spinal  nerves,  the  anterior 
divisions  of  the  sacral  nerves  communicate  with  the  sympathetic 
nerve;  and  the  communicating  cord  is  very  short,  the  ganglia  of  the 
latter  being  close  to  the  inner  margin  of  the  foramina  of  the  sacrum. 

The  first  four  nerves  (ihe  fourth  in  part)  contribute  to  form  the 
sacral  plexus.  The  fifth  has  no  share  in  the  plexus, — it  ends  in  the 
perineum.  The  fourth  and  fifth  nerves  have  therefore  some  peculiari- 
ties in  the  manner  of  their  distribution  ; and,  as  the  description  will 
occupy  but  a short  space,  these  two  nerves  will  be  noticed  first,  before 
the  details  of  the  other  nerves  and  the  numerous  branches  to  which 
they  give  rise  is  followed  out. 

The  Fourth  Sacral  Nerve. 

Only  one  part  of  the  anterior  division  of  this  nerve  joins  the  sacral 
plexus  ; the  remainder,  which  is  nearly  half  the  nerve,  supplies  branches 
to  the  viscera  and  muscles  of  the  pelvis,  and  sends  downwards  a 
connecting  filament  along  the  side  of  the  coccyx  to  the  fifth  nerve. 

The  visceral  branches  of  the  fourth  sacral  nerve  are  directed  forwards  to  the 
lower  part  of  the  bladder,  and  communicate  freely  with  branches  from  the  sym- 
pathetic nerve.  Numerous  offsets  are  distributed  to  the  neighbouring  viscera, 
according  to  the  sex ; they  will  be  described  with  the  pelvic  portion  of  the  sym- 
pathetic nerve.  The  foregoing  branches  are,  in  some  instances,  furnished  by  the 
third  sacral  nerve  instead  of  the  fourth. 

Of  the  rfmsadar  branches,  one  enters  the  levator  ani,  piercing  that  muscle  on  its 
pelvic  surface ; another,  in  some  cases,  penetrates  the  coccygeus,  whilst  a third 
supplies  the  external  sphincter  muscle  of  the  rectum.  The  last  branch,  after  passing 
either  through  the  coccygeus,  or  between  it  and  the  levator  ani.  reaches  the  peri- 
neum, and  is  distributed  likewise  to  the  integuments  between  the  anus  and  the 
coccyx. 

The  Fifth  Sacral  Nerve. 

The  anterior  division  of  this,  the  lowest  sacral  nerve,  runs  forwards 
through  the  coccygeus  muscle  opposite  the  junction  of  the  sacrum  and 
the  first  coccygeal  vertebra  it  then  descends  upon  the  coccygeus 

* The  nerve  occasionally  passes  through  a foramen  (fifth  sacral)  formed  between  the 
sacrum  and  the  coccyx. 


28* 


330 


SACRAL  PLEXUS. 


nearly  to  the  tip  of  the  coccyx,  where  it  turns  backwards  through  the 
fibres  of  that  muscle  and  the  gluteus  maximus,  and  ends  in  the  integu- 
ment upon  the  posterior  and  lateral  aspect  of  the  bone. 

As  soon  as  this  nerve  appears  in  front  of  the  bone  (in  the  pelvis),  it  is  joined 
by  the  descending  filament  from  the  fourth  nerve,  and  lower  down  by  the  small 
anterior  division  of  the  coccygeal  nerve.  It  supplies  small  filaments  to  the  coc- 
cygeus  muscle. 

The  Coccygeal  Nerve. 

The  anterior  division  of  the  coccygeal,  or,  as  it  is  sometimes  named, 
the  sixth  sacral  nerve,  is  a very  small  filament.  It  escapes  from  the 
spinal  canal  at  its  end,  pierces  the  sacro-sciatic  ligament  and  the 
coccygeus  muscle,  and  upon  the  side  of  the  coccyx  is  joined  with  the 
fifth  sacral  nerve,  partaking  in  the  distribution  of  that  nerve. 

THE  SACRAL  PLEXUS. 

The  lumbo-sacral  cord  (formed  as  before  described  by  the  junction 
of  the  fifth  and  part  of  the  fourth  lumbar  nerves),  the  anterior  divisions 
of  the  first  three  sacral  nerves  and  part  of  the  fourth,  unite  to  form 
this  plexus.  The  construction  of  the  plexus  differs  from  that  of  any 
other  of  the  plexuses  formed  by  the  spinal  nerves.  This  is  formed  by 
the  junction  of  the  several  constituent  nerves  into  one  broad  flat  cord. 
To  the  place  of  union  the  nerves  proceed  in  different  directions,  the 
upper  ones  being  very  oblique,  while  the  lower  are  nearly  horizontal  in 
their  course  ; and,  as  a consequence  of  this  difference  in  direction,  they 
diminish  in  length  from  the  first  to  the  last.  The  sacral  plexus,  thus 
constructed,  rests  on  the  anterior  surface  of  the  pyriform  muscle, 
opposite  the  side  of  the  sacrum.  It  is  broadest  at  the  upper  part, 
where  the  nerves  join,  and  narrow  at  the  lower  end,  where  it  escapes 
through  the  great  sacro-sciatic  foramen,  and  is  continued  into  or  ends 
in  the  great  sciatic  nerve. 

Branches. — The  sacral  plexus  supplies  the  larger  part  of  the  nerves 
of  the  lower  limb,  and  furnishes  some  small  offsets  to  structures  con- 
nected with  the  pelvis.  The  branches  are  the  following : — Small 
offsets  to  muscles  within  the  pelvis  (internal  obturator  and  pyriformis); 
and  to  other  muscles  on  the  back  of  the  pelvis  (gemelli  and  quadratus 
femoris) ; the  pudic  nerve;  the  small  sciatic  nerve,  and  the  great 
sciatic  nerve. 

Small  Muscular  Branches. 

The  small  nerves  supplied  to  muscles  situated  within  the  pelvis, 
and  to  others  on  its  outer  side,  will  be  placed  together  under  this 
head. 

To  the  pijriformis  muscle,  one  or  more  branches  are  given,  either 
from  the  plexus  or  from  the  upper  sacral  nerves  before  they  reach 
the  plexus. 

The  nerve  of  the  internal  obturator  muscle  arises  from  the  upper 
part  of  the  plexus — from  the  part,  therefore,  which  is  formed  by  the 
connexion  of  the  lumbo-sacral  and  the  first  sacral  nerves.  It  turns 
behind  the  spine  of  the  ischium  with  the  pudic  vessels,  and  is  then 
directed  forwards  through  the  small  sacro-sciatic  foramen  to  reach 
the  inner  surface  of  the  obturator  muscle. 


PUDIC  NERVE— BRANCHES. 


331 


The  superior  gemellus  receives  a small  branch,  which  arises  near 
the  pudic  nerve,  from  the  lower  part  of  the  plexus. 

The  little  nerve  which  supplies  the  lower  gemellus  and  quadratus 
femoris  muscles  springs  from  the  lower  part  of  the  plexus.  Concealed 
at  first  by  the  great  sciatic  nerve,  it  passes  beneath  the  gemelli  and 
the  tendon  of  the  internal  obturator, — between  those  muscles  and  the 
capsule  of  the  hip-joint, — and  reaches  the  deep  (anterior)  surface  of 
the  quadratus.  It  furnishes  a nerve  to  the  lower  gemellus,  as  well  as 
a small  articular  filament  to  the  back  part  of  the  hip-joint. 

In  some  cases  the  nerve  last  described  proceeds  from  the  upper  end  of  the 
sciatic  nerve  instead  of  the  plexus ; but  it  is  usually  derived  from  the  latter 
source  in  the  manner  already  mentioned. 

Pudic  Nerve. 

This  nerve,  fig.  371,  supplies  the  lower  end  of  the  rectum,  the  peri- 
neum, and  in  part  the  external  genital  organs.  Arising  from  the  lower 
part  of  the  sacral  plexus,  the  pudic  nerve  turns  behind  the  spine  of  the 
ischium,  and  then  passes  through  the  small  sacro-sciatic  foramen, 
where  it  usually  gives  off  an  inferior  hsemorrhoidal  branch.  It  is 
next  directed  upwards  and  forwards  along  the  outer  part  of  the 
ischio-rectal  fossa  with  the  pudic  vessels,  and  divides  into  two  termi- 
nal branches;  one  of  these  is  the  perineal  nerve,  the  other  ends  on  the 
dorsum  of  the  penis. 

a.  The  perineal  nerve,  the  lower  and  much  the  larger  of  the  two 
divisions  of  the  pudic  nerve,  lies  below  the  pudic  artery,  and  is  chiefly 
expended  in  branches  to  the  integument  (superficial  perineal).  It  like- 
wise supplies  offsets  to  several  muscles  and  slender  filaments  to  the 
corpus  spongiosum  urethrae;  some  of  these  latter,  before  penetrating 
the  erectile  tissue,  run  a considerable  distance  over  its  surface.. 

The  cutaneous  and  muscular  offsets  of  the  perineal  nerve  are  distri- 
buted as  follows : — 

The  superficial  perineal  branches  are  t^vvo  in  number,  and  are  distinguishable  as 
posterior  and  anterior.  The  posterior  one,  which  first  separates  from  the  perineal 
nerve,  reaches  the  back  part  of  the  ischio-rectal  fossa,  and  from  thence  turns 
forwards  in  company  with  the  anterior  branch  to  reach  the  scrotum.  Whilst  in 
the  fossa,  it  gives  filaments  inwards  to  the  sphincter  ani  and  to  the  skin  in  front 
of  the  anus.  It  communicates  with  the  anterior  branch  to  be  next  noticed,  as 
well  as  with  the  inferior  pudendal  branch  of  the  small  sciatic  nerve  and  the  infe- 
rior heemorrhoidal  nerve. — The  anterior  branch  descends  to  the  fore  part  of  the 
ischio-rectal  fossa;  and,  after  passing  forwards  with  the  superficial  perineal 
artery,  ramifies  in  the  skin  on  the  fore  part  of  the  scrotum  and  on  the  surface  of 
the  penis.  This  branch  sends  small  twigs  to  the  levator  ani  muscle  also. 

In  the  female,  both  the  superficial  perineal  branches  terminate  in  the  external 
labium  pudendi. 

The  muscular  branches  given  off  from  the  perineal  division  of  the  pudic  nerve 
generally  arise  by  a single  trunk,  which  is  directed  inwards  under  cover  of  the 
transversalis  perinei  muscle,  and  divides  into  several  offsets ; these  are  distributed 
among  the  muscles  of  the  perineum, — viz.,  the  transversalis  perinei,  erector  penis, 
accelerator  urinae,  and  compressor  urethrae. 

b.  The  dorsal  nerve  of  the  penis,  the  upper  division  of  the  pudio 
nerve,  continues  in  the  course  of  the  pudic  artery  between  the  layers 
of  the  deep  perineal  fascia,  and  afterwards  through  the  suspensory 
ligament  of  the  penis.  It  thus  reaches  the  dorsum  of  the  penis,  along 


332 


SMALL  SCIATIC  NERVE. 


which  it  passes  as  far  as  the  glans,  where  it  divides  info  filaments  for 
the  supply  of  that  part.  On  the  penis,  this  nerve  is  joined  by  branches 
of  the  sympathetic  system,  and  it  distributes  offsets  to  the  integument 
on  the  upper  surface  and  sides  of  tlie  organ,  including  the  prepuce. 
One  large  branch  penetrates  the  corpus  cavernosum  penis. 

In  the  female,  this  division  of  the  pudic  nerve  is  much  smaller  than 
in  the  male.  It  takes  a similar  course,  and  ends  upon  the  clitoris. 

The  inferior  hcemorrhuidal  nerve  arises  from  the  pudic  nerve  at  the 
back  of  the  pelvis,  or  directly  from  the  sacral  plexus.  It  is  transmitted 
through  the  small  sacro-sciatic  foramen,  and  then  descends  towards 
the  lower  end  of  the  rectum.  Some  of  the  branches  of  this  nerve  end 
in  the  external  sphincter  and  the  adjacent  skin  of  the  anus;  others, 
reach  the  skin  in  front  of  that  part,  and  communicate  with  the  inferior 
pudendal  branch  of  the  small  sciatic  nerve  and  with  the  superficial 
perineal  nerve. 

Small  Sciatic  Nerve. 

The  small  sciatic  nerve  (nervus  ischiadicus  minor)  is  chiefly  a 
cutaneous  nerve,  supplying  the  integument  over  the  posterior  aspect 
of  the  thigh  and  (to  a small  extent)  the  leg  ; it  also  furnishes  branches 
to  one  muscle — the  gluteus  maximus. 

This  nerve  is  formed  by  the  union  of  two  or  more  nervous  cords, 
derived  from  the  lower  part  of  the  sacral  plexus.  Leaving  the  pelvis 
through  the  great  sacro-sciatic  foramen  below  the  pyriform  muscle,  it 
descends  beneath  (before)  the  gluteus  maximus,  and  at  the  lower 
border  of  that  muscle  comes  into  contact  with  the  fascia  lata,  under 
W'hich  it  continues  its  course  dowmwards  along  the  back  of  the  limb. 
The  nerve  perforates  the  fascia  a little  below  the  knee,  fig.  372,  ^ and, 
thus  become  subcutaneous,  accompanies  the  short  saphenous  vein 
beyond  the  middle  of  the  leg.  Its  terminal  cutaneous  branches  com- 
municate with  the  short  saphenous  nerve. 

The  branches  of  the  small  sciatic  nerve  are  as  follows; — 

The  inferior  gluteal  branches. — These  are  given  off  under  the  gluteus  maximus, 
and  supply  the  lower  part  of  that  muscle. — A distinct  gluteal  branch  commpnly 
proceeds  from  the  sacral  plexus  to  the  upper  part  of  the  muscle. 

The  principal  cutaneous  brancRes  of  the  nerve  escape  from  beneath  the  lower 
border  of  the  gluteus  maximus;  they  form  an  external  and  an  internal  set. 

The  internal  branches  are  mostly  distributed  to  the  skin  of  the  inner  side  of  the 
thigh  at  its  upper  part.  One,  however,  which  is  much  longer  than  the  rest, 
the  inferior  pudendal  branch,  turns  forwards  below  the  tuberosity  of  the  ischium  to 
reach  the  perineum.  Having  pierced  the  fascia  lata,  on  the  outer  side  of  the 
ramus  of  that  bone,  the  cutaneous  filaments  of  this  branch  extend  forward  to  the 
front  and  outer  part  of  the  scrotum,  and  communicate  with  the  superficial  peri- 
neal nerve. 

In  the  female,  the  inferior  pudendal  branch  is  distributed  to  the  external  labium 
pudendi. 

The  external  cutaneous  branches,  two  or  three  in  number,  turn  upwards  in  a 
retrograde  course  to  the  skin  over  the  outer  part  of  the  great  gluteal  muscle.  In 
some  instances  one  takes  a different  course,  descending  and  ramifying  in  the  in- 
teguments over  the  outer  sidepf  the  thigh  nearly  to  the  middle. 

Whilst  descending  beneath  the  fascia  of  the  thigh,  the  small  sciatic  nerve  sends 
off  some  other  small  cutaneous  filaments.  One  of  these,  arising  somewhat  above 
the  knee-joint,  perforates  the  fascia,  and  is  prolonged  over  the  popliteal  region  to 
the  upper  part  of  the  leg. 


GREAT  SCIATIC  NERVE— BRANCHES. 


333 


GREAT  SCIATIC  NERVE.-. 


The  great  sciatic  nerve  (nervus  ischiadicus),  fig.  371,  the  largest 
nerve  in  the  body,  distributes  offsets  to  the  back 
of  the  thigh,  and  supplies  the  leg  and  the  foot  S'*?-  371. 


with  their  nerves. 

This  large  nerve  is  the  continuation  of  the 
lower  end  of  the  sacral  plexus,  as  that  escapes 
from  the  pelvis  through  the  sacro-sciatic  fora- 
men, below  the  pyriformis  muscle.  Placed 
deeply  at  the  back  of  the  limb,  the  nerve 
reaches  down  below'  the  middle  of  the  thigh, 
where  it  divides  into  two  large  bi'anches,  named 
the  internal  popliteal  and  external  popliteal 
nerves.  The  bifurcation  of  the  large  nerve 
may  take  place,  however,  at  any  point  inter- 
mediate between  the  sacral  plexus  and  the 
lower  part  of  the  thigh  ; and,  occasionally,  it  is 
found  to  occur  even  within  the  pelvis,  a portion 
of  the  pyriformis  muscle  being  interposed  be- 
tween the  two  great  parts  into  which  the  nerve 
divides. 

At  first  the  great  sciatic  nerve  lies  in  the 
hollow'  between  the  great  trochanter  of  the 
femur  and  the  tuberosity  of  the  ischium,  to- 
gether with  the  small  sciatic  nerve  and  the 
sciatic  artery,  (a  branch  of  this  artery  running 
in  the  substance  of  the  nerve.)  It  is  here 
covered  by  the  gluteus  maximus,  and  rests  on 
the  external  rotator  muscles  of  the  thigh.  Lower 
down  it  is  in  contact,  in  front,  with  the  adductor 
magnus,  and  is  covered  (behind)  by  the  long 
head  of  the  biceps  muscle. 

Branches.  — In  its  course  downwards,  the 
great  sciatic  nerve  supplies  offsets  to  some  con- 
tiguous parts,  viz.,  to  the  hip-joint,  and  to  the 
muscles  at  the  back  of  the  thigh. 

The  artimlar  branches  are  derived  from  the  upper  end 
of  the  nerve,  and  enter  the  capsular  ligament  of  the 
hip-joint,  on  its  posterior  aspect.  They  sometimes 
arise  from  the  sacral  plexus. 

The  muscular  branches  are  given  off  beneath  the 
biceps  muscle ; they  supply  the  flexors  of  the  leg,  viz., 
the  biceps,  semitendinosus,  and  semimembranosus. 
A branch  is  likewise  given  to  the  adductor  mrignus. 

Fig.  371.  Plan  of  the  great  and  small  sciatic  nerves.  1.  Supe- 
rior gluteal  nerve.  2.  Pudic  nerve.  3 Small  sciatic  nerve.  5. 
Inferior  pudendal  branch.  6.  Continuation  of  the  small  sciatic  in 
the  thigh.  7.  Great  sciatic  nerve.  8.  Internal  popliteal  nerve. 
9.  Posterior  tibial  nerve.  10,  12.  Short  saphenous  nerve.  11. 
Peroneal  communicating  branch.  13.  External  popliteal  or  pero- 
neal nerve. 


334 


INTERNAL  POPLITEAL  NERVE— BRANCHES. 


The  two  large  branches  into  which  the  great  sciatic  nerve  divides 
are  distributed  to  the  limb  from  the  knee  downwards,  one  (the  internal 
popliteal)  supplying  the  back  of  the  leg  and  the  sole  of  the  foot;  while 
the  other  (external  popliteal)  supplies  the  fore  part  of  the  leg  and  the 
dorsum  of  the  foot. 

INTERNAL  POPLITEAL  NERVE. 

The  internal  popliteal  nerve,*  fig.  371,®,  the  larger  of  the  two  divi- 
sions, following  tlie  same  direction  as  the  parent  trunk,  continues 
along  the  back  part  of  the  thigh  and  through  the  middle  of  the  popli- 
teal space.  It  lies  at  first  at  a considerable  distance  from  the  popliteal 
artery  (at  its  outer  side  and  nearer  to  the  surface)  ; but,  from  th(j 
knee-joint  downwards,  is  close  to  the  vessel,  and  crosses  over  it  to  the 
inner  side.  The  nerve  is  covered  at  first  by  the  biceps  muscle,  and 
afterwards  has  the  same  connexions  with  the  neighbouring  parts  as 
the  popliteal  blood-vessels. 

Branches. — The  internal  popliteal  nerve  supplies  branches  to  the 
knee-joint,  to  the  muscles  of  the  calf  of  the  leg,  as  well  as  to  the  skin 
on  the  posterior  aspect  of  the  leg,  and  6n  the  dorsum  of  the  foot  at  its 
outer  margin.  They  are  disposed  as  follows  : — 

Articular  Nerves. 

The  articular  branches  are  generally  three  in  number:  two  of  these  accompany 
the  upper  and  lower  articular  arteries  of  the  inner  side  of  the  knee-joint,  the  third 
follows  the  middle  or  azygos  artery.  These  lierves  pierce  the  ligamentous  tissue 
of  the  jo’mt. — The  upper  one  is  wanting  in  some  cases. 

Muscular  Branches! 

The  muscular  branches  of  the  internal  popliteal  nerve  arise  behind  the  knee- 
joint,  while  the  nerve  is  between  the  heads  of  the  gastrocnemius  muscle  : — 

A single  branch,  which  soon  bifurcates,  supplies  the  two  parts  of  the  gaatrocm- 
mius.  The  small  nerve  of  the  plantaris  muscle  is  derived  from  the  branch  just 
described,  or  from  the  main  trunk  (internal  popliteal).  The  solens  receives  a 
branch  of  considerable  size,  which  enters  the  muscle  on  its  posterior  aspect  after 
descending  to  it  in  front  of  the  gastrocnemius.  Lying  deeper  than  the  preceding 
branches,  and  arising  somewhat  below  the  joint,  is  the  nerveA)f  the  popliieus  mus- 
cle. It  descends  along  the  outer  side  of  the  popliteal  vessels ; and,  after  turning 
beneath  the  lower  border  of  the  muscle,  enters  its  deep  or  anterior  surface. 

Short  or  E.vtemal  Saphenous  Nerve. 

The  cutaneous  branch  of  the  internal  popliteal  nerve  (ramus  communicans  nervi 
tibiei, — Jordensjf  communicans  tibialis, — auctor.  var.)  may  be  named  as  above, 

* The  inner  division  of  the  sci.itie  nerve,  from  its  commencement  to  its  partition  at  the 
foot,  is  generally  described  in  anatomical  works  without  any  separation- into  parts;  and  the 
name  applied  by  different  writers  to  this  long  cord,  as  might  be  expected,  varies  considers, 
bly,  e.  g.  “ crnralis  internus,”  or  “popliieus  internus,” — Winslow:  “tibialis  posterior,” — 
Haller:  “ scialique  poplite  interne.” — Sabatier:  “libicus,” — Jordens":  “ tibialis  vel  libicus,” 
— Fischer,  <Sec.  One  or  other  of  the  foregoing  names,  or  some  modification  of  them,  is 
used  by  more  modern  writers. 

As  the  terms  “ popliteal”  and  “tibial,”  which  are  the  bases  of  this  varied  nomenclature, 
are  adapted  respectively  to  only  a particular  portion  of  the  entire  nerve,  it  is  probably  best 
to  divide  it  into  parts,  and  to  apply  to  each  part  the  appropriate  designation.  This 
arrangement  has  the  advantage  of  a nearer  correspondence  with  the  manner  of  dividing 
the  blood-vessels. 

t This  nerve,  and  the  offset  of  the  external  popliteal  nerve  which  joins  it,  appear  to  have 
been  first  named  from  the  fact  of  their  connexion  one  with  the  other  by  Jordens  (“  De- 


FOSTERIOR  TIBIAL  NERVE. 

because  of  its  following  very  nearly  the  course  of  the 
short  saphenous  vein.  It  descends  along  the  leg  be- 
neath the  fascia,  resting  on  the  gastrocnemius  (at  first 
between  the  heads  of  the  muscle)  to  about  midway 
between  the  knee  and  the  foot.  Here  it  perforates  the 
fascia,  (fig.  372,“,)  and  is  usually  joined  by  a branch 
from  the  external  popliteal  nerve  (communicans  pero- 
nei).  After  receiving  this  communicating  branch,  the 
short  saphenous  nerve  descends  beneath  the  integu- 
ment near  the  outer  side  of  the  tendo-achillis  in  com- 
pany with  the  short  saphenous  vein,  and  turns  for- 
ward beneath  the  outer  malleolus  to  end  in  the  skin 
at  the  side  of  the  foot  and  on  the  little  toe.  On  the 
dorsum  of  the  foot  this  nerve  communicates  with  the 
musculo-cutaneous  nerve. 

In  some  cases,  the  short  saphenous  nerve  supplies 
the  outer  side  of  the  fourth  toe,  as  well  as  the  little 
toe.  The  union  between  the  saphenous  nerve  and  the 
offset  of  the  external  popliteal  nerve  occurs  in  some 
cases  higher  than  usual,  occasionally  even  at  or  close 
to  the  popliteal  space.  It  sometimes  happens  that  the 
communication  between  the  nerves  is  altogether 
wanting. 

Fig.  372.  Plan  of  the  cutaneous  nerves  on  the  posterior  aspect 
of  the  leg.  1.  Inner  division  of  the  internal  cutaneous  nerve. 

2,2.  Branches  of  the  long  saphenous.  3.  Small  sciatic  become 
cutaneous  ; the  offset  above  it  in  a direct  line  is  a branch  of  the 
same  nerve.  4,  6.  Short  saphenous  nerve.  5.  Peroneal  com- 
municating nerve. 

POSTERIOR  TIBIAL  NERVE. 

From  the  lower  margin  of  the  popliteus  muscle,  where  it  assumes 
this  designation,  the  nerve  continues  with  the  posterior  tibial  artery, 
lying  for  a short  space  at  the  inner  side  and  afterwards  at  the  outer 
side  of  the  vessel,  as  far  as  the  interval  between  the  inner  malleolus 
and  ihe  heel ; and  here  it  divides  into  the  two  plantar  nerves  (internal 
and  external).  The  posterior  tibial  nerve,  like  the  vessels,  is  covered 
at  first  by  the  muscles  of  the  calf  of  the  leg,  afterwards  only  by  the  in- 
tegument and  fascia,  and  it  rests  against  the  deep-seated  muscles. 

Branches. — The  deep  muscles  on  the  back  of  the  leg  and  integu- 
ment of  the  sole  of  the  foot  receive  branches,  which  leave  the  poste- 
rior tibial  nerve  in  its  course  along  the  leg. 

0.  The  muscular  branches  emanate  from  the  upper  part  of  the  nerve,  either  sepa- 
rately or  by  a single  common  trunk ; and  one  is  distributed  to  each  of  the  follow- 
ing muscles,  viz.,  the  tibialis  posticus,  the  long  flexor  of  the  toes,  and  the  long 

scriptio  Nervi  Iscbiadici,”  Erlangse,  1788).  This  manner  of  designating  the  branches  in 
question  was  followed  very  generally  by  anatomical  writers  until  late  years,  and  it  has 
been  adopted  by  most  neurologists, — e.  g.,  Fischer  (“  Descript.  Anatom.  Nerv.  lumbalium, 
sacrahum  et  extremitatum  inferiorum,”  Lipsiaa,  1791) ; Bock  (“  Abbildungen  der  Riieken- 
marksnerven,”  &c , Leipzig,  1827.) 

Boyer  and  Bichat,  in  their  general  treatises  on  Anatomy,  have  named  the  offset  of  the 
internal  popliteal  nerve  “ external  saphenous and  it  is  not  uncommon  to  find,  in  modern 
books,  this  name  and  the  older  nomenclature  mi.xed  up  in  the  following  manner  : — The 
two  branches,  before  their  junction,  are  named  “ communicating”  branches  of  the  tibial 
and  peroneal  nerves  respectively;  and  the  nerve  resulting  from  their  union  is  the  external 
saphenous  nerve.  M.  Cruveilhier,  again,  treats  of  the  two  branches  as  “ tibial  saphenous” 
and  “ peroneal  saphenous.” 


335 


Fig.  372, 


6 


336 


EXTERNAL  PLANTAR  NERVE. 


flexor  of  the  great  toe.  The  branch  which  supplies  the  last-named  muscle  runs 
along  the  peroneal  artery  before  penetrating  the  muscle. 

b.  The  plantar  cutaneous  branch,  furnished  from  the  posterior  tibial  nerve,  perfo- 
rates the  internal  annular  ligament,  and  ramifies  in  the  integument  at  the  inner 
side  of  the  sole  of  the  foot  and  beneath  the  heel. 

Internal  Plantar  Nerve. 

The  internai  plantar,  the  larger  of  the  two  nerves  furnished  to  the 
sole  of  the  foot,  accompanies  the  internal  or  smaller  plantar  artery, 
and  supplies  the  nerves  to  both  sides  of  the  three  inner  toes,  and  to  one 
side  of  the  fourth.  From  the  point  at  which  it  separates  from  the 
posterior  tibial  nerve,  it  is  directed  forwards  under  cover  of  the  ab- 
ductor of  the  great  toe,  and  divides,  opposite  the  posterior  end  of  the 
metatarsus  at  the  interval  between  the  muscle  just  named  and  the 
short  flexor  of  the  toes,  into  four  digital  branches,  and  at  the  same 
time  communicates  with  the  external  plantar  nerve. 

Branches. — As  the  internal  plantar  nerve  courses  forwards,  small 
offsets  are  supplied  to  the  abductor  pollicis  and  flexor  brevis  digito- 
rum ; and  some  small  branches  perforate  the  plantar  fascia  to  ramify 
in  the  integument  of  the  sole  of  the  foot. 

The  digital  branches,  which  are  named  numerically  from  within 
outwards,  (the  innermost  being  first,  and  so  on,)  pass  from  under 
cover  of  the  plantar  fascia  behind  the  clefts  between  the  toes.  The 
first  or  innermost  branch  continues  single,  but  the  other  three  bifur- 
cate to  supply  the  adjacent  sides  of  two  toes.  These  branches  require 
separate  notice. 

The  first  digital  branch  is  that  destined  for  the  inner  side  of  the  great  toe ; it 
becomes  subcutaneous  farther  back  than  the  others,  and  sends  off  a branch  to 
the  short  flexor  muscle  of  this  toe. 

The  second  branch,  having  reached  the  interval  between  the  first  and  second 
metatarsal  bones,  furnishes  a small  offset  to  the  first  lumbricalis  muscle,  and 
bifurcates  some  way  behind  the  cleft  between  the  great  toe  and  the  second  to 
supply  their  contiguous  sides. 

The  third  digital  branch  corresponds  with  the  second  interosseous  space,  gives 
a slender  filament  to  the  second  lumbricalis  muscle,  and  divides  in  a manner 
similar  to  the  second  branch  into  two  offsets  for  the  sides  of  the  second  and  third 
toes. 

The  fourth  digital  branch  crosses  to  the  third  space,  and  is  distributed  to  the 
adjacent  sides  of  the  third  and  fourth  toes.  It  receives  a communicating  branch 
from  the  external  plantar  nerve. 

Along  the  sides  of  the  toes,  cutaneous  and  articular  filaments  are 
given  from  these  digital  nerves;  and,  opposite  the  ungual  phalanx, 
each  gives  a dorsal  branch  to  the  parts  beneath  the  nail,  and  then  runs 
on  to  the  pulp  of  the  toe,  where  it  is  distributed  like  the  nerves  of  the 
fingers. 

External  Plantar  Nerve. 

The  external  plantar  nerve  completes  the  supply  of  digital  nervesjto 
the  toes,  furnishing  therefore  branches  to  the  little  toe  and  half  the 
fourth ; and  gives  a deep  branch  of  considerable  size,  which  is  distri-  , 
buted  to  several  of  the  short  muscles  in  the  sole  of  the  foot. 

This  nerve  runs  obliquely  forwards  towards  the  outer  side  of  the  i 
foot  with  the  external  plantar  artery,  between  the  flexor  brevis  digito- 


EXTERNAL  POPLITEAL  NERVE. 


337 


rum  and  the  flexor  accessorius,  as  far  as  the  interval  between  the 
former  of  these  muscles  and  the  abductor  of  tbe  little  toe.  Here  it 
divides  into  a superficial  and  a deep  branch,  having  previously  fur- 
nished offsets  to  the  flexor  accessorius  and  the  abductor  digiti  minimi. 

a.  The  superficial  division  separates  into  two  digital  branches, 
which  have  the  same  general  arrangement  as  the  digital  branches  of 
the  internal  plantar  nerve.  They  are  distributed  thus  : — 

Digital  branches. — One  of  the  digital  branches  continues  undivided,  and  runs 
along  the  outer  side  of  the  little  toe.  It  is  smaller  than  the  other,  and  pierces  the 
plantar  fascia  further  back.  The  short  flexor  muscle  of  the  little  toe  and  the  two 
interosseous  muscles  of  the  fourth  metatarsal  space  receive  branches  from  this 
nerve. 

The  larger  digital  branch  communicates  with  an  offset  from  the  internal  plantar 
nerve^  and  bifurcates  behind  the  cleft  between  the  fourth  and  fifth  toes  to  supply 
one  side  of  each. 

b.  The  deep  or  muscular  branch  of  the  external  plantar  nerve  dips 
into  the  sole  of  the  foot  with  the  external  plantar  artery,  under  cover 
of  the  tendons  of  the  flexor  muscles  and  the  adductor  pollicis,  and  ter- 
minates in  numerous  branches  for  the  following  muscles: — all  the  in- 
terossei  (dorsal  and  plantar)  except  one  or  both  of  those  in  the  fourth 
space,  the  two  outer  lumbricales,  the  adductor  pollicis,  and  the  trans- 
versalis  pedis. 

THE  EXTERNAL  POPLITEAL  OR  PERONEAL  NERVE. 

This  nerve,*  fig.  371,  descends  obliquely  along  the  outer  side  of  the 
popliteal  space,  lying  close  to  the  biceps  muscle.  Continuing  down- 
wards over  the  outer  part  of  the  gastrocnemius  muscle  (between  it 
and  the  biceps)  to  the  fibula  below  its  head,  the  nerve  turns  round  that 
bone,  passing  between  it  and  the  peroneus  longus  muscle,  and  then 
divides  into  the  anterior  tibial  and  ihe  musculo-cutaneous  nerves. 

Some  articular  and  cutaneous  branches  are  derived  from  the  ex- 
ternal popliteal  nerve  before  it  divides. 

Articular  Nerves. 

Tire  articular  branches,  two  in  number,  are  conducted  to  the  outer  side  of  the 
capsular  ligament  of  the  knee-joint  by  the  upper  and  lower  articular  arteries  of 
that  side.  They  sometimes  arise  together,  and  the  upper  one  occasionally  springs 
from  the  great  sciatic  nerve  before  its  bifurcation. 

From  the  place  of  division  of  the  external  popliteal  nerve,  a recurrent  articular 
nerve  ascends  through  the  tibialis  anticus  muscle  with  the  recurrent  artery  to 
reach  the  fore  part  of  the  knee-joint. 

Cutaneous  Nerves.. 

The  cutaneous  branches,  two  or  tlrree  in  number,  supply  the  skin  on  the  back 
•part  and  outer  side  of  the  leg.  The  largest  of  these  is  the  peroneal  communicating 
bmnch  (r.  communicans  peronei, — Jordens;  communicans  flbularis),  (fig.  372,  ■’,) 
which  joins  about  the  middle  of  the  back  of  the  leg  with  the  short  saphenous 
nerve  as  already  mentioned  in  the  description  of  that  nerve.  In  some  instances, 
however,  it  continues  a separate  branch  and  reaches  down  to  the  heel. 

' Another  cutaneous  branch  extends  along  the  outer  side  of  the  leg  to  the  middle 
or  lower  part,  sending  offsets  both  backwards  and  forwards,  fig.  373,=. 

* “ Small  sciatic  ramus  or  sciaticus  externus,” — Winslow  : “ tibialis  anterior,  exterior,” 
—Haller : “ sciatique  poplite  externe,” — Sabatier  : “ peroneus,” — Jordens ; “ peroneus  seu 
popliteus  externus,” — Fischer, 

VOL.  II. 


29 


338 


ANTERIOR  TIBIAL  NERVE. 


MUSCULO-CUTANEOTJS  NERVE. 

The  musculo-cutaneous  (peroneal)  nerve  is  the  principal  cutaneous 
nerve  of  the  dorsum  of  the  foot,  and  also  supplies  the  muscles  on  the 
outer  part  of  the  leg.  It  descends  between  the  peronei  muscles  and 
the  long  extensor  of  the  toes,  and  reaches  the 
Fig^.  373.  surface  by  perforating  the  fascia  in  the  lower 

part  of  the  leg  on  its  anterior  aspect.  As  soon 
as  the  nerve  becomes  subcutaneous,  fig.  373,3  or 
even  before,  it  divides  into  two  branches,  distin- 
guished as  external  and  internal.  When  the 
division  occurs  while  the  nerve  is  in  contact 
with  the  muscles,  the  two  branches  may  be 
found  to  perforate  the  fascia  at  different  heights. 

Whilst  between  the  muscles,  the  musculo- 
cutaneous nerve  gives  its  muscular  branches  to 
the  peroneus  longus  and  peroneus  brevis ; and, 
before  its  final  division,  some  cutaneous  offsets 
are  distributed  to  the  lower  part  of  the  leg. 

The  internal  division  of  the  musculo-cutaneous  nerve, 
fig.  373,  passing  forwards  along  the  dorsum  of  the  foot, 
furnishes  a branch  to  the  inner  side  of  the  great  toe,  Etna 
other  branches  to  the  contiguous  sides  of  the  second 
and  third  toes.  It  also  gives  offsets,  which  extend  over 
the  inner  ankle  and  the  corresponding  side  of  the  foot- 
This  nerve  communicates  with  the  long  saphenous 
nerve  on  the  inner  side  of  the  foot,  and  with  the  ante- 
rior tibial  nerve  between  the  great  toe  and  the  second 
toe. 

The  external  division,  larger  than  the  internal  one, 
courses  over  the  foot  towards  the  fourth  toe,  which, 
together  with  the  contiguous  borders  -of  the  third  and 
fifth  toes,  it  supplies  with  branches.  Cutaneous  nerved. 
Plan  of  the  cutaneous  derived  from  this  branch,  spread  over  the  outer  ankle 
nerves  on  the  fore  part  of  and  the  outer  side  of  the  foot,  where  it  is  connected 
the  leg,  and  the  dorsum  of  ^vith  the  short  saphenous  nerve. 

the  foot.  1.  Long  saphenous,  dorsal  digital  nerves  are  continued  on  to  the  last 

Branches  of  the  external  po-  phalanges  of  the  tOes. 

pliieal.  3.  Mu.sculo-cutaneous.  The  number  of  toes  supplied  by  each  of  the  two 
4.  Anterior  tibial.  divisions  of  the  musculo-cutaneous  nerve  is  liable  to 

vary;  together,  they  commonly  supply  all  the  toes  on 
their  dorsal  aspect,  excepting  the  outer  side  of  the  little  toe,  which  receives  a 
branch  from  the  short  saphenous  nerve,  and  the  adjacent  sides  of  the  great  toe 
and  the  second  toe,  to  which  the  anterior  tibial  nerve  sends  a branch. 

ANTERIOR  TIBIAL  NERVE. 

The  anterior  tibial  (interosseous  nerve),  like  the  preceding  nerve, 
extends  through  the  leg  to  the  foot,  and  supplies  muscular  and  cuta- 
neous branches;  but  this  nerve  is  more  deeply  placed,  and  is  distributed 
chiefly  to  muscles,  while  the  largest  part  of  the  musculo-cutaneous 
nerve  is  given  to  the  integument. 

Commencing  between  the  fibula  and  the  peroneus  longus,  the  ante- 
rior tibial  nerve  inclines  obliquely  beneath  the  long  extensor  of  the 


THE  SYMPATHETIC  NERVE. 


339 


toes  to  the  fore  part  of  the  interosseous  membrane,  on  which  structure 
it  comes  into  contact  with  the  anterior  tibial  vessels,  fig.  369 ; and 
with  those  vessels  (having  the  same  connexions  with  neighbouring 
parts)  it  descends  to  the  front  of  the  ankle-joint,  where  it  divides  into 
an  external  and  an  internal  branch.  The  nerve  first  reaches  the  outer 
side  of  the  anterior  tibial  artery,  above  the  middle  of  the  leg ; and, 
after  crossing  in  front  of  that  vessel  once  or  oftener,  lies  to  its  outer 
side  at  the  bend  of  the  ankle. 

In  its  course  along  the  leg,  the  anterior  tibial  nerve  gives  slender 
filaments  to  the  muscles  between  whioh  it  is  placed,  namely,  the 
tibialis  anticus,  the  long  extensor  of  the  toes,  and  the  proper  extensor 
of  the  great  toe. 

The  more  external  of  the  two  branches  which  result  from  the  division  of  the 
anterior  tibial  nerve,  turns  outwards  over  the  tarsus  beneath  the  short  extensor  of 
the  toes ; and;  having  become  enlarged  (like  the  posterior  interosseous  nerve  on 
the  wrist)  terminates  in  branches  which  supply  the  short  extensor  muscle,  and 
hkewise  the  articulations  of  the  foot. 

The  internal  branch,  continuing  onwards  in  the  direction  of  the  anterior  tibial 
nerve,  accompanies  the  dorsal  artery  of  the  foot  to  the  first  interosseous  space, 
and  ends  in  two  branches,  fig.  373,^  which  supply  the  integument  on  the  neigh- 
bouring sides  of  the  great  toe  and  the  second  toe  on  their  dorsal  aspect.  It  com- 
municates with  the  internal  division  of  the  musculo-cutaneous  nerve. 

Summary. — The  great  sciatic  nerve  with  its  divisions  supplies  the 
integument  of  the  leg,  with  the  exception  of  a part  which  derives 
nerves  from  the  small  sciatic  and  the  anterior  crural  nerve.  It  like- 
wise supplies  the  muscles  on  the  back  of  the  thigh,  and  those  of  the 
leg  and  foot.  The  several  joints  of  the  lower  limb  receive  filaments 
from  the  same  nerve. 


THE  SYMPATHETIC  NERVE. 

The  sympathetic  system  of  nerves  (nervus  infercostalis  ; nerfs  de  la 
vie  organique — Bichat). — The  viscera  generally  are  supplied  with 
nerves  from  this  system,  but  some  organs  likewise  receive  offsets 
from  the  cerebro-spinal  system,  as  the  lungs,  the  heart,  and  the  upper 
and  lower  ends  of  the  alimentary  canal.  The  characters  by  which 
the  sympathetic  nerve  is  distinguished  having  been  already  pointed 
out,  it  is  only  necessary  to  say  in  this  place  that  it  is  reddish  or  gray 
in  colour,  and  that  it  is  softer  in  texture  than  the  cerebro-spinal 
nerves. 

In  this  system  three  parts  may  be  distinguished,  as  follows: — 
a.  The  part  which  first  requires  notice  is  to  be  regarded  as  the 
centre  of  the  sympathetic.  It  consists  of  two  gangliated  cords — or  of 
a series  of  ganglia  placed  longitudinally,  and  connected  by  intervening 
cords, — situate  along  the  fore  part  of  the  vertebral  column,  at  the 
sides,  for  the  most  part,  of  the  bodies  of  the  vertebrae,  and  extending 
from  the  base  of  the  skull  to  the  coccyx.  The  two  cords  lie  parallel 


340 


SYMPATHETIC  NERVE-ITS  DIVISIONS. 


one  to  the  other  as  far  as  the  sacrum,  on  which  bone  they  gradually 
converge,  till  they  both  terminate  in  a single  ganglion  on  the  coccyx. 
This  long  cord  is  considered  divisible  into  parts  corresponding  with 
the  divisions  of  the  vertebral  column  ; and  thus,  cervical,  dorsal, 
lumbar,  and  sacral  portions  are  recognised. 

The  ganglia  are  equal  in  number  to  the  vertebrse  on  which  they  lie, 
except  in  the  neck,  where  there  are  but  three.  These  bodies  are  con- 
veniently regarded  as  so  many  centres,  receiving  nerves,  and  dis- 
tributing offsets  to  the  viscera.  They  are  severally  connected  with 
the  spinal  nerves  in  their  neighbourhood  by  means  of  short  cords;  and 
each  connecting  cord  consists  of  a white  and  a gray  portion,  the 
former  proceeding  from  the  spinal  nerve  to  the  ganglion,  while  the 
latter  takes  the  opposite  course — from  the  ganglion  to  the  spinai 
nerve.  At  its  upper  end  the  gangliated  cord  likewise  communicates 
with  certain  cranial  nerves. — The  cords  intervening  between  the 
ganglia,  like  those  connecting  the  ganglia  with  the  spinal  nerves,  are 
compounded  of  a gray  and  a white  part,  the  latter  being  continuous 
with  the  portions  of  spinal  nerves  already  traced  to  the  ganglia. 

From  the  ganglia,  or  their  intervening  cords,  offsets  are  given  for 
the  supply  of  the  viscera;  and  these  offsets  follow  the  course  of  the 
arteries  to  the  organs  for  which  they  are  destined.  Branches  are 
likewise  sent  to  join  the  large  prevertebral  plexuses  to  be  presently 
noticed.  The  offsets  from  the  ganglia  partake  of  both  kinds  of  nerves 
(the  proper  sympathetic  and  the  spinal  systems),  the  nerves  or  roots 
which  join  the  ganglia  from  the  spinal  system,  being  continued 
onwards  with  others  which  originate  in  the  ganglia.  From  this  cir- 
cumstance, and  the  facts  above  mentioned  respecting  the  constitution 
of  the  gangliated  cord,  it  follows  that  the  so-named  sympathetic  nerve 
is  composed  of  two  forms  of  nerve-fibre  : one  of  which  is  peculiar,  and 
originates  in  the  ganglia  of  the  sympathetic  system,  while  the  other  is 
borrowed  from  the  cerebro-spinal  nerve.* 

b.  The  second  division  of  the  sympathetic  comprises  three  large 
aggregations  of  nerves,  or  nerves  and  ganglia  situated  in  front  of  the 
spine  (prevertebral  plexuses),  and  occupying  respectively  the  thorax, 
the  abdomen,  and  the  pelvis.  They  are  single  or  unsymmetrical,  and 
are  named  respectively  the  cardiac,  the  solar,  and  the  hypogastric 
plexus.  These  plexuses  each  receive  branches  from  both  the  gangliated 
cords  above  noticed,  and  they  constitute  centres  from  which  the  vis- 
cera are  supplied  with  nerves. 

c.  In  the  third  series  will  be  ranged  certain  small  ganglia  which 
are  dispersed  through  the  cranium  at  irregular  intervals.  These  are 
connected  more  or  less  directly  with  the  upper  part  of  the  gangliated 
cords,  and  more  immediately  with  the  fifth  pair  of  cranial  nerves. 
They  furnish  branches  for  the  most  part  to  the  organs  of  sense  ? and 
they  are  known  as  the  ophthalmic,  the  spheno-palatine,  otic,  and  sub- 
maxillary  ganglia. 

The  ganglia  last  referred  to  having  been  before  fully  described  in 

• For  an  account  of  the  microscopical  appearance  of  tlie  sympathetic  nerve,  see  the 
General  Anatomy  of  Nerve. 


UPPER  CARDIAC  NERVE. 


341 


connexion  with  the  fifth  pair  of  cranial  nerves,  it  remains  to  enter  here 
into  the  details  of  the  first  two  divisions  of  the  sympathetic  system. 

A.  THE  GANGLIATED  CORDS. 

1.  THE  CERVICAL  PART. 

In  the  neck  each  gangliated  cord  is  deeply  placed  beneath  the  sheath 
of  the  great  cervical  blood-vessels,  and  is  in  contact  with  the  muscles 
which  immediately  cover  the  fore  part  of  the  vertebral  column.  It 
comprises  but  three  ganglia,  which  are  distinguished  by  their  relative 
position,  being  placed  respectively  at  the  upper  and  lower  end  and  the 
middle  of  the  neck.  The  ganglia  require  to  be  separately  described. 

THE  UPPER  CERVICAL  GANGLION. 

This  is  the  largest  of  the  ganglia  of  the  gangliated  cord.  It  is 
usually  fusiform  in  shape:  but  there  is  a good  deal  of  variety  in  this 
respect  in  different  cases,  the  ganglion  being  occasionally  broader 
than  usual  (in  various  degrees),  and  from  time  to  time  constricted  at 
intervals.*  It  has  the  reddish-gray  colour  characteristic  of  the  ganglia 
of  the  sympathetic  system ; and  it  is  placed  on  the  larger  rectus  mus- 
cle, opposite  the  second  and  third  cervical  vertebrae,  and  beneath  the 
internal  carotid  artery. 

Connexion  with  spinal  nerves. — At  its  outer  side  the  superior  cer- 
vical ganglion  is  connected  w'ith  the  first  four  spinal  nerves,  and  the 
connecting  cords  have  the  arrangement  before  pointed  out  in  the 
general  description  (page  339). 

Connexion  with  cranial  nerves. — Small  branches  connect  the  gan- 
glion or  its  cranial  cord,  with  the  second  ganglion  of  the  pneurno- 
gastric,  and  with  the  ninth  cranial  nerve  near  the  base  of  the  skull. 
And  in  this  place  may  likewisb  be  noticed  another  branch,  which  is 
directed  upwards  from  the  cord  issuing  from  the  upper  part  of  the 
ganglion,  and  divides  at  the  base  of  the  skull  into  two  filaments.  One 
of  these  ends  in  the  second  (petrosal)  ganglion  of  the  glosso-pharyngeal 
nerve  ; while  the  other,  entering  the  jugular  foramen,  joins  the  ganglion 
of  the  root  of  the  pneumogastric. 

BRANCHES  OF  THE  GANGLION. 

/ 

Pharyngeal  Nerves  and  Pharyngeal  Plexus. 

These  nerves  arise  from  the  upper  part  of  the  ganglion,  and  are  di- 
rected obliquely  inwards  to  the  side  of  the  pharynx.  Opposite  the 
middle  constrictor  muscle  they  .unite  with  branches  of  the  pneumo- 
gastric and  glosso-pharyngeal  nerves;  and  by  their  union  with  those 
nerves  the  pharyngeal  plexus  is  constructed.  Branches  emanating 
from  the  plexus  are  distributed  to  the  muscles  and  mucous  membrane 
of  the  pharynx. 

* The  occurrence  of  constrictions  has  given  rise  to  the  opinion  that  the  ganglion  may 
result  from  the  coalescence  of  several  ganglia;  and  in  this  way  it  has  been  sought  to  ac- 
count for  its  greater  size,  and  for  the  diminished  number  of  the  cervical  ganglia. 

29* 


342 


VASCULAR  BRANCHES. 


Upper  Cardiac  Nerve. 

A few  preliminary  remarks  on  the  cardiac  nerves  are  here  necessary. 
The  cervical  ganglia  of  the  sympathetic  furnish  each  a cardiac  branch, 
named,  like  the  ganglion  from  which  it  arises,  upper,  middle,  and 
lower;  but  the  branches  are  not  altogether  disposed  in  the  same  way 
on  the  opposite  sides  of  the  body,  and  we  shall  therefore  have  to  notice 
the  two  sides  separately. 

The  cardiac  nerves  are  continued  singly,  or  in  connexion,  to  the 
large  prevertebral  plexus  (cardiac  plexus)  of  the  thorax.  In  this,  as 
in  other  parts  of  the  sympathetic  system,  considerable  variety  occurs 
as  to  the  disposition  of  the  branches  in  different  cases;  and  where  one 
branch  happens  to  be  of  smaller  size  than  common,  another  will  be 
found  to  possess  an  increased  size,  as  if  to  compensate  for  the  defect. 
But  the  arrangement  of  the  branches  at  their  termination  in  the  organs 
to  which  they  are  distributed  appears  to  be  always  the  same. 

The  upper  cardiac  nerve  (r.  cardiacus  superficialis)  of  the  right  side, 
is  constructed  from  two  or  more  branches  of  the  ganglion,  with,  in 
some  instances,  an  offset  from  the  cord  connecting  the  first  two  gan- 
glia, lu  its  course  in  the  neck  the  nerve  lies  behind  the  carotid  sheath, 
in  contact  with  the  longus  colli  muscle ; and  it  is  placed  over  the  lower 
thyroid  artery  and  the  recurrent  laryngeal  nerve.  Entering  the  thorax, 
it  passes,  in  some  cases  before,  in  others  behind  the  subclavian  artery, 
and  is  directed  along  the  innominate  artery  to  the  back  part  of  the 
arch  of  the  aorta,  where  it  ends  in  the  deep  cardiac  plexus,  a few 
small  filaments  continuing  also  to  the  front  of  the  great  vessel.  Some 
branches  are  distributed  to  the  thyroid  body;  they  accompany  the  in- 
ferior thyroid  artery. 

In  its  course  downwards  the  cardiac  nerve  is  repeatedly  connected 
with  other  branches  of  the  sympathetic,  and  with  the  pneumogastric 
nerve.  Thus,  about  the  middle  of  the  neck  it  is  joined  by  some  fila- 
ments from  the  external  laryngeal  nerve ; and,  rather  lower  down,  by 
one  or  more  filaments  from  the  trunk  of  the  pneumogastric  nerve; 
lastly,  on  entering  the  chest,  it  joins  with  the  recurrent  laryngeal. 
Instead  of  passing  to  the  thorax  in  the  manner  above  described,  the 
nerve  may  be  found  to  join  the  cardiac  branch  furnished  from  one  of 
the  other  cervical  ganglia.* 

The  superficial  cardiac  nerve  of  the  left  side  has,  while  in  the  neck, 
the  same  course  and  connexions  as  that  of  the  right  side.  But  within 
the  chest  it  follows  the  left  carotid  artery  to  the  arch  of  the  aorta,  and 
ends  in  some  instances  in  the  superficial  cardiac  plexus,  while  in  others 
it  joins  the  deep  plexus ; and  accordingly  it  passes  either  in  front  of 
the  arch  of  the  aorta  or  behind  it. 

Vascular  Branches. 

The  nerves  which  ramify  on  the  arteries  (nervi  molles)  spring  from 
the  front  of  the  ganglion,  and  reach  the  trunk  of  the  carotid  artery, 
which  they  entwine.  An  offset  is  continued  on  each  branch  of  the 

* Scarpa  describes  this  as  the  common  disposition  of  the  superficial  cardiac  nerve,  but 
M.  Cruveilhier  (Anat.  Descript.,  t.  iv.)  states  that  he  has  not  in  any  case  found  the  cardiac 
nerves  exactly  to  correspond  with  the  figures  of  the  “Tabulce  Neurologicse.” 


CAROTID  PLEXUS. 


343 


external  carotid,  and  forms  a slender  plexus  upon  it.  These  nerves 
or  plexuses  have  the  same  designation  as  the  arteries  they  surround. 
From  the  plexus  on  the  facial  artery  is  derived  the  filament  which  joins 
the  submaxillary  ganglion ; and,  from  that  on  the  middle  meningeal 
artery,  offsets  have  been  described  as  extending  to  the  otic  ganglion, 
as  well  as  to  the  gangliform  enlargement  of  the  facial  nerve  (ante, 
page  279  and  fig.  357.)  Lastly,  a communication  is  established  between 
the  plexus  on  the  carotid  artery  and  the  digastric  branch  of  the  facial 
nerve. 

Small  ganglia  are  occasionally  found  on  some  of  the  foregoing  vas- 
cular plexuses,  close  to  the  origin  of  the  vessels  with  which  they  are 
associated.  Those  which  have  been  described  are  an  inter-carotid  one 
(placed  in  the  angle  of  the  bifurcation  of  the  common  carotid  artery), 
and  lingual,  temporal,  and  pharyngeal  ganglia. 

The  foregoing  branches  will  be  found  to  correspond  in  a great 
measure  with  the  branches  of  other  ganglia ; but  we  now  proceed  to 
examine  an  offset  which  is  peculiar  to  the  first  cervical  ganglion. 

Ascending  or  Cranial  Branch. 

The  ascending  offset  of  the  first  cervical  ganglion  is  soft  in  texture 
and  of  a reddish  tint,  seeming  to  be  in  some  degree  a prolongation  of 
the  ganglion  itself.  In  its  course  to  the  skull,  it  is  concealed  by  the 
internal  carotid  artery,  with  which  it  enters  the  carotid  canal  in  the 
temporal  bone;  and  it  is  then  divided  into  two  parts,  which  are  placed 
one  on  the  outer  side,  the  other  on  the  inner  side  of  the  vessel. 

The  external  fart,  or  division,  distributes  filaments  to  the  internal 
carotid  artery,  and,  after  communicating  by  means  of  other  filaments 
with  the  internal  division  of  the  cord,  forms  the  carotid  plexus. 

The  inner  division,  rather  the  smaller  of  the  two,  also  supplies  fila- 
ments to  the  carotid  artery,  and  goes  to  form  what  is  named  the 
cavernous  plexus.  The  several  parts  of  these  divisions  of  the  cranial 
cord  are  prolonged  on  the  trunk  of  the  internal  carotid,  and  extend  to 
the  cerebral  and  ophthalmic  arteries,  around  which  they  form  secon- 
dary plexuses.*  One  plexus  enters  the  eyeball  with  the  central  artery 
of  the  retina. 

Carotid  Plexus. 

The  carotid  plexus,  situate,  as  before  mentioned,  on  the  outer  side 
of  the  internal  carotid  artery  at  its  second  bend  (reckoning  from  below), 
or  between  the  second  or  third  bends,  joins  the  fifth  and  sixth  nerves, 
and  gives  many  filaments  to  the  vessel  on  which  it  lies.f 

Branches. — 1.  The  connexion  with  the  sixth  nerve  is  established  by  means  of 
one  or  two  filaments  of  considerable  size,  which  are  applied  to  that  nerve  where 
it  lies  by  the  side  of  the  internal  carotid  artery. 

2.  The  filaments  connected  with  the  Gasserian  ganglion  of  the  fifth  nerve  pro- 
ceed in  one  case  from  the  carotid  plexus,  in  another  from  the  cavernous. 

* It  was  said  by  Ribes  (Mem.  de  la  Societe  Med.  d’Emulation,  tom.  viii.  p.  606,)  that 
the  cranial  prolongations  of  the  sympathetic  nerve  from  both  sides  were  joined  one  with 
the  other  on  the  anterior  communicating  artery, — a small  ganglion  or  a plexus  being 
formed  at  the  point  of  juncture.  This  connexion  has  not  been  satisfactorily  made  out  by 
other  observers. 

t Valentin  describes  nerves  furnished  to  the  dura  mater  from  this  plexus. 


344 


MIDDLE  CARDIAC  NERVE. 


3.  The  filament  which  constitutes  the  deep  branch  or  part  of  the  vidian  nerve  is 
directed  forwards  to  the  pterygoid  canal,  through  the  cartilaginous  substance 
closing  the  foramen  lacerum  anterius  in  the  base  of  the  skull.  In  that  canal  it 
becomes  associated  with  the  deep  branch  of  the  vidian,  and  is  continued  forward 
to  the  spheiio-palatine  ganglion.  fSee  ante,  page  272.) 

Cavernous  Plexus. 

The  cavernous  plexus,  named  from  its  position  in  the  sinus  of  the 
same  name,  is  placed  below  and  rather  to  the  inner  side  of  the  highest 
turn  of  the  internal  carotid  artery.  Besides  giving  branches  on  the 
artery,  it  communicates  with  the  third,  the  fourth,  and  fifth  cranial 
nerves  which  enter  the  orbit.* 

Branches. — 1.  The  filament  which  joins  the  third  nerve  comes  into  connexion 
with  it  close  to  the  pomt  of  division  of  that  nerve. 

2.  The  branch  to  the  fourth  nerve,  which  may  be  derived  from  either  the  caver- 
nous or  carotid  plexus,  joins  the  nerve  where  it  lies  in  the  waU  of  the  cavernous 
sinus. 

3.  The  filaments  connected  with  the  ophthalmic  division  of  the  fifth  nerve  are 
supplied  to  its  inner  surface.  One  of  them  is  continued  forward  to  the  lenticular 
ganglion,  either  in  connexion  with,  or  distinct  from  the  nasal  nerve  (ante,  267), 

MIDDLE  CERVICAL  GANGLION. 

The  middle  ganglion  (ganglion  thyroideum),  which  is  much  the 
smallest  of  the  cervical  ganglia,  is  placed  on  or  near  the  inferior  thy- 
roid artery.  It  is  usually  connected  in  the  ordinary  way  with  the 
fifth  and  the  sixth  spinal  nerves,  but  the  communication  with  those 
nerves  is  not  constant. 

BRANCHES  DERIVED  FROM  THE  GANGLION. 

Thyroid  branches. — From  the  inner  side  of  the  ganglion  some  nerves 
proceed  along  the  inferior  thyroid  artery  to  the  thyroid  body,  where 
they  join  the  recurrent  laryngeal  and  the  external  laryngeal  nerves. 
Whilst  on  the  artery,  these  branches  communicate  with  the  upper 
cardiac  nerve. 

Middle  Cardiac  Nerve. 

The  middle  cardiac  nerve  (nervus  cardiacus  profundus  v.  magnu.s) 
is  prolonged  to  the  chest  beneath  the  sheath  of  the  common  carotid 
artery,  and  in  front  of  the  subclavian  artery,  or,  it  may  be,  behind  this 
vessel.  In  the  chest  it  lies  on  the  trachea,  where  it  is  joined  by  fila- 
ments of  the  recurrent  laryngeal  nerve,  and  it  ends  in  the  right  side  of 
the  deep  cardiac  plexus.  While  in  the  neck,  the  nerve  communicates 
with  the  upper  cardiac  nerve  and  the  recurrent  branch  of  the  pneumo- 
gastric. — When  the  middle  cervical  ganglion  is  small,  the  middle 
cardiac  nerve  may  be  found  to  be  an  oflset  of  the  inter-ganglionic 
cord. 

The  foregoing  account  of  the  nerve  has  reference  to  the  right  side 
of  the  body  : on  the  left  side,  the  middle  cardiac  nerve  enters  the  chest 
between  the  left  carotid  and  subclavian  arteries,  and  joins  the  left 
side  of  the  deep  cardiac  plexus. 

• A second  communication  between  the  sympathetic  and  the  sixth  nerve,  taking  place 
below  the  bend  of  the  carotid,  has  been  described  by  some  anatomists. 


GANGLIATED  CORD  IN  THORAX. 


345 


LOWER  CERVICAL  GANGLION. 

The  lower  or  third  cervical  ganglion  is  irregular  in  shape,  usually 
somewhat  round  or  semilunar,  and  is  frequently  united  in  part  to  the 
first  thoracic  ganglion.  Placed  in  a hollow  between  the  transverse 
process  of  the  last  cervical  vertebra  and  the  neck  of  the  first  rib,  it  is 
concealed  by  the  vertebral  artery. 

Connexion  with  spinal  nerves. — This  ganglion  is  connected  directly 
by  short  communicating  cords,  in  the  manner  of  other  ganglia,  with 
the  last  two  cervical  nerves.  Moreover,  branches  which  pass  from 
the  ganglion  along  the  vertebral  artery,  supplying  twigs  to  this  vessel, 
are  also  connected  with  other  cervical  nerves,  and  thus  additional 
communications  are  established  between  the  two  systems. 

BRANCHES  OF  THE  LOWER  CERVICAL  GANGLION. 

Lower  Cardiac  Nerve. 

The  lower  cardiac  nerve,  issuing  from  the  third  cervical  ganglion 
or  from  the  first  thoracic,  and  inclining  inwards  behind  the  subclavian 
artery,  terminates,  like  the  other  cardiac  nerves,  in  the  cardiac  plexus 
behind  the  arch  of  the  aorta.  It  communicates  with  the  middle  cardiac 
and  recurrent  laryngeal  nerves  behind  the  subclavian  artery.  On  the 
left  side,  the  lower  cardiac  often  becomes  blended  with  the  middle 
cardiac  nerve,  and  the  cord  resulting  from  their  union  terminates  in 
the  deep  cardiac  plexus. 

Branches  on  the  vertebral  artery;  vertebral  plexus. — From  the 
lowest  cervical  and  the  first  dorsal  ganglia  a few  slender  branches 
ascend  along  the  vertebral  artery  in  its  osseous  canal,  forming  a plexus 
round  the  vessel  by  their  intercommunications,  and  supplying  it  with 
ofisets.*  This  plexus  is  connected  with  the  cervical  spinal  nerves  as 
far  upwards  as  the  fourth. 

A couple  of  branches  pass  from  the  lower  cervical  ganglion  to  the 
first  dorsal  ganglion  in  front  of  the  subclavian  artery,  forming  loops 
round  the  vessel  (ansee  Vieussenii),  and  supplying  it  with  small  offsets. 

2.  THORACIC  PART  OF  THE  GANGLIATED  CORD. 

In  the  thorax  the  knotted  cord  is  placed  on  each  side  of  the  spinal 
column,  over  the  line  of  the  heads  of  the  ribs;  and  it  is  uninterrupt- 
edly continuous  with  the  same  part  in  the  neck  and  in  the  abdomen. 
It  is  covered  by  the  pleura. 

Opposite  the  head  of  each  rib  the  cord  presents  for  the  most  part  a 
grayish  enlargement  or  ganglion,  so  that  there  are  commonly  twelve 
of  these ; but,  from  the  occasional  coalescence  of  two  masses,  the  num- 
ber is  uncertain.  The  first  ganglion  is  much  larger  than  the  rest,  and 
is  of  an  elongated  form.  It  is  often  blended  with  the  lower  cervical 
ganglion.  The  rest  are  small,  and  are  not  inaptly  described  as 
hordeiform. 

* Little  gangliform  enlargements  have  been  described  as  existing  on  the  plexus,  but 
they  do  not  possess  the  vesicles  which  belong  to  true  ganglia  (Valentin).  The  existence 
of  the  enlargements  in  question  is  doubted  by  M.  Cruveilhier. 


346 


GREAT  SPLANCHNIC  NERVE. 


A represenlalion  of  the  ganglia  of 
the  sympathetic  in  the  chest;  (the 
ganglia  are  represented  larger  than 
natural.)  The  wood-cut  is  taken  from 
part  of  a plate  in  Mr.  Swan's  work. 
a.  Aorta,  h.  First  rib.  c.  Eleventh 
rib.  I.  First  thoracic  ganglion.  2. 
Last  thoracic  ganglion.  3.  Large 
splanchnic  nerve.  4.  Small  splanch- 
nic nerve.  5.  Smallest  splanchnic 
nerve.  6.  Part  of  the  brachial  plexus. 


The  branches  furnished  by  the  first  six 
gavglia,  fig.  374,  are  much  smaller  than 
those  of  the  lower  six,  and  are  distributed 
in  a great  measure  to  the  thoracic  aorta, 
the  vertebras,  and  ligaments.  One  or  two 
branches  enter  the  posterior  pulmonary 
plexus.* 

The  branches  furnished  by  the  loiver 
six  ganglia  unite  into  cords,  which  pass 
from  the  thorax  to  the  abdomen,  and  join 
plexuses  in  the  latter  cavity.  The  cords 
referred  to  are  three  in  number  on  each 
side,  are  named  splanchnic,”  and  are 
distinguished  as  the  great,  the  small,  and 
the  smallest  splanchnic  nerve.f  They 
occur  in  the  thorax  in  the  order  in  which 
they  are  here  mentioned,  the  largest  being 
at  the  same  time  highest,  and  the  smallest 
lower  than  the  rest. 


The  Great  Splanchnic  Nerve. 

This  nerve  or  cord,  fig.  374,®  appears 
at  first  sight  to  be  formed  by  roots  supplied 
by  the  thoracic  ganglia  from  the  sixth  or 
seventh  to  the  tenth  inclusive ; but,  by  examination  after  immersion 
in  acetic  or  diluted  nitric  acid,  small  filaments  may  be  traced  upwards 
as  far  as  the  third  ganglion,  or  even,  according  to  Mr.  Beck,  as  far  as 
the  first.J 

Gradually  augmented  by  the  successive  addition  of  the  several  roots, 
the  cord  descends  obliquely  inwards  over  the  bodies  of  the  dorsal 
vertebrae;  and,  after  perforating  the  crus  of  the  diaphragm,  (the  point 
at  which  it  passes  through  the  muscle  varying  in  different  cases,) 


Fig.  374. 


Connexion  with  the  spinal  nerves. — The 
branches  of  connexion  between  the  spinal 
nerves  and  the  ganglia  of  the  sympathe- 
tic, fig.  374,  are  usually  two  in  number 
for  each  ganglion. 


* Mr.  Swan  represents  branches  of  the  second,  third,  and  fourth  ganglia  as  united  in  a 
plexus  (which  he  names  thoracic)  on  the  bodies  of  tlie  vertebrae.  Offsets  from  the  plexus 
are  mentioned  by  this  anatomist  as  entering  the  pulmonary  and  cardiac  plexuses,  while 
some  are  continued  beneath  the  oesophagus  to  tlie  corresponding  plexus  on  the  opposite 
side. 

t VVrisberg  noticed  a fourth  splanchnic  nerve,  which  he  found  but  eight  times,  though 
he  sought  it  in  many  bodies.  He  proposed  to  call  it  the  highest  splanchnic  nerve  (nervus 
splanclinicus  supremus).  It  is  described  as  formed  by  offsets  from  the  cardiac  nerves,  and 
from  the  lower  cervical,  as  well  as  some  of  the  upper  thoracie  ganglia.  Consult  the  “Ob- 
serv.  Anatom,  de  Nerv.  Viscerum  particula  prima,”  p.  25,  sect.  iij.  “ De  nervo  sympathico 
maximo.” 

t See  a paper  entitled  “ On  the  Nerves  of  the  Uterus,  by  J.  S.  Beck,  Esq.,”  in  the  Philo, 
sophical  Transactions,  Part  2,  for  1846. 


LUMBAR  GANGLIA. 


347 


terminates  in  the  semilunar  ganglion,  frequently  also  sending  some 
filaments  to  the  renal  plexus  and  the  suprarenal  body. 

The  splanchnic  nerve  is  remarkable  from  its  white  colour  and  firm- 
ness, which  are  owing  to  the  preponderance  of  the  spinal  nerve-fibre 
in  its  composition. 

In  the  chest  the  great  splanchnic  nerve  is  not  unfrequently  divided  into  parts; 
and  forms  a little  plexus  ■with  the  small  splanchnic  nerve.  Occasionally,  too,  a 
small  ganglion  (ganglion  splanchnicum)  is  formed  on  it  over  the  last  dorsal  verte- 
bra, or  the  last  but  one  3 and  when  it  presents  a plexiform  arrangement,  several 
small  ganglia  have  been  observed  on  its  divisions. 

Small  Splanchnic  Nerve. 

The  small  or  second  splanchnic  nerve,  fig.  374,^  springs  from  the 
tenth  and  eleventh  ganglia,  and  from  the  cord  between  those  ganglia. 
It  continues  with  the  preceding  nerve  through  the  diaphragm,  and 
ends  in  the  coeliac  plexus.  In  the  chest  this  nerve  often  communicates 
with  the  large  splanchnic  nerve ; and  in  some  instances  it  furnishes 
filaments  to  the  renal  plexus,  especially  if  the  lowest  splanchnic  nerve 
is  very  small  or  wanting. 

Smallest,  or  Third  Splanchnic  Nerve. 

This  nerve  (nerv.  renalis  posterior — Walter),  fig.  374,®,  arises  from 
the  last  thoracic  ganglion,  and  communicates  sometimes  with  the 
nerve  last  described.  , After  piercing  the  diaphragm,  it  ends  in  the 
renal  plexus,  and  in  the  lowest  part  of  the  coeliac  plexus. 

3.  LUMBAR  PART  OF  THE  GANGLIATED  CORD. 

In  the  lumbar  region  the  tw'o  gangliated  cords,  continuing  from  the 
thoracic  series  of  ganglia  behind  the  diaphragm,  approach  one  to  the 
other  more  nearly  than  in  the  thorax.  They  are  placed  before  the 
bodies  of  the  vertebrse,  each  lying  along  the  inner  margin  of  the  psoas 
muscle ; and  that  of  the  right  side  is  partly  covered  by  the  vena  cava. 

The  ganglia  are  small,  and  hordeiform  in  shape.  They  are  com- 
monly four  in  number,  but  occasionally  their  number  is  diminished, 
and  then  their  size  is  proportionably  enlarged. 

Connexion  with  spinal  nerves. — In  consequence  of  the  greater  dis- 
tance at  which  the  lumbar  ganglia  are  separated  from  the  interverte- 
bral foramina  of  the  spine,  the  cords  connecting  them  with  the  spinal 
lumbar  nerves  are  longer  than  in  other  parts  of  the  sympathetic 
system.  There  are  generally  two  connecting  cords  for  each  ganglion, 
but  the  number  is  not  so  uniform  as  it  is  in  the  chest;  nor  are  those 
belonging  to  any  one  ganglion  connected  with  the  same  spinal  nerve 
in  all  cases. 

The  connecting  cords  accompany  the  lumbar  arteries,  and,  as  they 
cross  the  bodies  of  the  vertehrm,  are  covered  by  the  fibrous  bands 
from  which  the  larger  psoas  muscle  partly  takes  its  origin. 

Branches  of  the  Lumbar  Ganglia. 

The  branches  of  these  ganglia  are  uncertain  in  their  number.  Some 
join  a plexus  on  the  aorta ; others  descending  go  to  form  the  hypo- 


348 


CARDIAC  PLEXUS. 


gastric  plexus.  Several  filaments  are  distributed  to  the  vertebrae,  and 
to  the  ligaments  connecting  those  bones. 

4.  SACRAL  part  OF  THE  GANGLIATED  CORD. 

Over  the  sacrum  the  gangliated  cord  of  the  sympathetic  nerve  is 
much  diminished  in  size,  and  gives  but  few  branches  to  the  viscera. 
Its  position  on  the  front  of  the  sacrum  is  along  the  inner  side  of  the 
anterior  sacral  foramina  ; and,  like  the  two  series  of  those  foramina, 
the  two  cords  approach  one  another  in  their  progress  downwards. 
The  upper  end  of  each  is  connected  with  the  last  lumbar  ganglion, 
sometimes  by  a double  inter-ganglionic  cord ; at  the  opposite  end,  the 
lowest  sacral  ganglion  is  connected  with  that  of  the  other  side  by 
means  of  a single  median  ganglion.  This  ganglion  {ganglion  hnpar) 
is  placed  on  the  fore  part  of  the  coccyx.  The  sacral  ganglia  are 
usually  five  in  number;  but  the  want  of  constancy  both  in  size  and 
number  is  more  marked  in  these  than  in  the  thoracic  or  lumbar 
ganglia. 

Connexion  with  spinal  nerves. — From  the  proximity  of  the  sacral 
ganglia  to  the  spinal  nerves  at  their  emergence  from  the  bone,  the 
communicating  branches  are  very  short : they  are  two  in  number  for 
each  ganglion,  and  are  in  some  cases  connected  with  two  ditferent 
sacral  nerves.  The  coccygeal  nerve  communicates  with  the  last 
sacral  or  the  coccygeal  ganglion. 

Branches  of  the  Sacral  Ganglia. 

The  branches  are  much  smaller  in  size  than  those  from  the  ganglia 
in  other  parts  of  the  cord.  They  are  for  the'  most  part  expended  on 
the  front  of  the  sacrum,  and  they  join  the  corresponding  branches 
from  the  opposite  side.  Some  filaments  from  one  or  two  of  the  first 
ganglia  enter  the  hypogastric  plexus,  while  others  go  to  form  a plexus 
on  the  middle  sacral  artery.  B'rom  the  lower  end  of  the  sympathetic 
(i.  e.,  the  loop  connecting  the  two  cords,  and  on  which  the  coccygeal 
ganglion  is  formed),  filaments  are  given  to  the  coccyx  and  the  ligaments 
about  it. 

B.  PREVERTEBRAL  PART  OF  THE  SYMPATHETIC  NERVE. 

This  portion  of  the  sympathetic  system,  it  has  been  already  stated, 
consists  of  certain  unsymmetrical  plexuses  placed  before  the  spine, 
and  serving  as  centres  from  which  nerves  are  furnished  to  the  viscera. 
Those  recognised  are  the  cardiac,  solar,  and  hypogastric  plexuses. 
They  are  composed  of  assemblages  of  nerves,  or  nerves  and  ganglia. 
Each  receives  nerves  from  the  gangliated  cord  of  both  sides;  and 
these  nerves,  as  will  presently  appear  in  the  special  description  of  the 
plexuses,  take  origin  from  the  ganglia  at  a distance  above  the  plexus. 

From  the  plexuses  are  furnished  branches  or  secondary  plexuses 
for  the  supply  of  the  viscera.  These  offsets  accompany  the  arteries  in 
their  course  to  the  viscera  for  which  they  are  respectively  destined. 

1.  CARDIAC  PLEXUS. 

The  prevertebral  plexus  of  the  thorax  is  thus  named.  To  it  several 


DEEP  CARDIAC  PLEXUS. 


349 


branches  (cardiac),  given  from  the  cervical  ganglia  of  the  sympathetic, 
and  from  the  vagus  nerve,  converge  as  to  a common  centre;  and 
from  it  proceed  the  nerves  which  supply  the  heart,  as  well  as  some 
offsets  which  assist  in  supplying  the  lungs. 

The  large  cardiac  plexus  of  nerves  lies  above  the  base  of  the  heart 
upon  the  two  great  arteries  which  issue  from  it  (aorta,  and  pulmonary 
arter^.  In  the  general  network  formed  by  these  nerves  there  are 
reck^ed  two  subdivisions,  which  are  partially  separated  one  from 
the  other,  and  are  distinguished  as  the  superficial,  and  the  deep  or 
great  cardiac  plexus.  The  branches  pass  from  these  to  the  heart,  in 
two  bundles,  which  accompany  the  nutritious  arteries  of  the  organ,  and 
from  this  circumstance  are  called  coronary  plexuses. 

Superficial  Cardiac  Plexus. 

The  superficial  cardiac  plexus  lies  in  the  concavity  of  the  arch  of 
the  aorta,  in  front  of  the  right  branch  of  the  pulmonary  artery.  In  it 
terminates  the  superficial  or  first  cardiac  nerve  of  the  left  side,  either 
wholly  or  in  part,  with  the  lower  cardiac  branch  of  the  left  pneumo- 
gastric  nerve  (in  some  cases,  also,  that  of  the  right  side) ; and  it  is 
joined  by  a prolongation  forward  from  the  deep  cardiac  plexus.  A 
small  ganglion  {ganglion  of  Wrisherg)  is  frequently  found  at  the  point 
of  union  of  the  nerves.  The  plexus  ends  in  the  anterior  coronary 
plexus,  and  it  furnishes  laterally  filaments  along  the  pulmonary  artery 
to  the  anterior  pulmonary  plexus  of  the  left  side. 

The  anterior  coronary  -plexus,  a prolongation  in  greatest  part  from 
the  superficial  cardiac  plexus  above  described,  is  at  first  continued 
forward  between  the  aorta  and  the  pulmonary  artery,  and  is  thence 
conducted  by  the  right  or  anterior  coronary  artery  to  the  heart. 
Where  the  anterior  coronary  artery  appears  between  the  large  vessels, 
the  coronary  plexus  receives  an  accession  from  the  deep  cardiac 
plexus. 

Deep  Cardiac  Plexus. 

The  deep  cardiac  plexus  (plexus  magnus  profundus — Scarpa),  is 
much  larger  than  the  superficial  one,  and  is  placed  behind  the  arch  of 
the  aorta,  between  it  and  the  end  of  the  trachea,  and  above  the  division 
of  the  pulmonary  artery. 

This  plexus  receives  all  the  cardiac  branches  of  the  cervical  ganglia 
of  the  sympathetic  nerve,  except  the  first  one  (superficial  cardiac  nerve) 
of  the  left  side.  It  likewise  receives  the  cardiac  nerves  furnished  by 
the  vagus  and  by  the  recurrent  laryngeal  branch  of  that  nerve,  with 
the  exception  of  the  lower  cardiac  nerve  of  the  left  side. 

The  nerves  issuing  from  the  great  cardiac  plexus  end  in  greatest 
part  in  the  posterior  coronary  plexus.  But  some  join  the  anterior 
coronary  plexus ; and  a few  filaments  are  added  to  the  pulmonary 
plexuses. 

There  is  some  difference  as  to  the  course  pursued  by  the  nerves  issuing  from 
the  plexus  on  the  right  and  left  side.  The  branches  descending  from  the  right 
side  of  the  plexus  pass,  some  in  front  of  the  right  pulmonary  artery,  others  behind 
the  vessel.  The  former,  which  is  much  the  more  numerous  set,  after  sending 

VOL.  II.  30 


350 


^SOLAR  PLEXUS. 


some  filaments  to  the  anterior  pulmonary  plexus,  are  directed  along  the  trunk  of 
the  pulmonary  artery,  and  become  part  of  the  anterior  coronary  plexus ; while 
the  nerves  stated  to  be  behind  the  right  pulmonary  artery  are  distributed  to  the 
right  auricle  of  the  heart,  and  a few  filaments  are  contmued  into  the  posterior 
coronary  plexus. 

On  the  left  side,  a few  branches  pass  forward  by  the  ductus  arteriosus  to  join 
the  superficial  cardiac  ple.xus;  but  the  great  body  of  the  nerves  of  this  side  end 
in  the  posterior  coronary  plexus,  after  giving  branches  to  the  left  auricle  of  the 
heart,  and  to  the  anterior  pulmonary  plexus. 

The  'posterior  coronary  plexus  is  derived  chiefly  from  the  left  side  of 
the  deep  cardiac  plexus,  but  is  joined  by  nerves  from  the  right  portion 
of  that  plexus.  It  surrounds  the  branches  of  the  coronary  artery  at 
the  back  of  the  heart,  and  supplies  mostly  the  muscular  substance  of 
the  ventricles. 

The  nerves  constituting  the  coronary  plexuses  accompany,  as  already  stated, 
the  branches  of  the  arteries,  and,  after  subdividing  minutely,  enter  the  muscular 
substance  of  the  heart.  Nervous  filaments  are  said  to  ramify  under  the  lining 
membrane  of  the  heart,  but  they  are  not  as  easily  distinguished  in  man  as  in  some 
animals,  the  sheep  for  example  (Valentin).  Ganglia  of  small  size  have  been 
found  by  Remak  * on  the  branches  of  the  cardiac  nerves  in  several  mammifers, 
both  on  the  surface  of  the  heart  and  in  the  muscular  substance,  where  they  were 
observed  to  be  very  numerous;  but  Valentin  failed  to  detect  such  ganglia  in  the 
human  heart. 

2.  EPIGASTRIC  OR  SOLAR  PLEXUS. 

The  epigastric  plexus,  which  is  the  largest  of  the  prevertebral 
plexuses,  is  placed  at  the  upper  part  of  the  abdomen,  behind  the 
stomach,  and  in  front  of  the  aorta  and  the  pillars  of  the  diaphragm. 
Surrounding  the  origin  of  the  coeliac  axis  and  the  upper  mesenteric 
artery,  it  occupies  the  interval  between  the  suprarenal  bodies,  and 
extends  downwards  as  far  as  the  pancreas.  The  plexus  consists  of 
nervous  cords,  and  several  ganglia  of  various  size  connected  together 
by  nervous  cords.  The  large  splanchnic  nerves  of  both  sides,  and 
some  branches  from  the  pneumogastric,  terminate  in  it.  The  offsets 
or  branches  sent  from  it  are  very  numerous,  and  they  accompany  the 
arteries  to  the  principal  viscera  of  the  abdomen,  constituting  so  many 
secondary  plexuses  on  the  vessels. 

Ganglia. — The  solar  plexus  contains,  as  already  mentioned,  several 
ganglia;  and  by  the  presence  of  these  bodies,  and  their  size,  it  is  di.-;- 
tinguished  from  the  other  prevertebral  plexuses.  Two  of  the  ganglia 
(one  for  each  side),  which  differ  from  the  rest  by  their  greater  size, 
require  separate  notice.  Named  semilunar,  though  they  have  often 
little  of  the  form  the  name  implies,  they  occupy  the  upper  and  outer 
part  of  the  plexus  on  each  side,  and  are  placed  close  to  the  suprarenal 
bodies,  by  the  side  of  the  cceliac  and*  the  superior  mesenteric  arteries. 
At  the  upper  end,  which  is  expanded,  each  ganglion  receives  the  great 
splanchnic  nerve,  and  from  it,  branches  radiate  in  different  directions. 

Offsets  from  the  plexus. — These  have  the  same  plexiform  arrange- 
ment as  the  large  plexus  from  which  they  are  derived.  Each  secon- 
dary plexus,  as  it  accompanies  a branch  of  the  aorta,  surrounds  the 
vessel  with  a kind  of  membranous  sheath,  and  is  named  from  the 


* Muller’s  Archiv,  1844. 


PLEXUSES  IN  ABDOMEN. 


351 


vessel  by  which  it  is  supported.  Accordingly,  diaphragmatic,  cceliac, 
renal,  mesenteric,  and  other  plexuses  are  recognised. 

Diaphragmatic  Plexuses. 

The  nerves  (inferior  diaphragmatic)  composing  each  of  these 
plexuses  are  derived  from  the  upper  part  of  the  semilunar  ganglion, 
and  are  larger  on  the  right  than  on  the  left  side.  Accompanying  the 
arteries  along  the  lower  surface  of  the  diaphragm,  the  nerves  sink 
into  the  substance  of  the  muscle.  They  furnish  some  filaments  to  the 
suprarenal  body,  and  join  with  the  spinal  phrenic  nerves. 

At  the  right  side,  on  the  under  surface  of  the  diaphragm,  and  near 
the  suprarenal  body,  there  is  a small  ganglion  {gang,  diaphragma- 
ticum),  which  marks  the  junction  between  the  phrenic  nerves  of  the 
spinal  and  the  sympathetic  systems.  From  this  small  ganglion  fila- 
ments are  distributed  to  the  vena  cava,  the  suprarenal  body,  and  the 
hepatic  plexus.  On  the  left  side  the  ganglion  is  wanting,  but  some 
filaments  are  prolonged  to  the  hepatic  plexus. 

Suprarenal  Plexus. 

The  suprarenal  nerves  issue  from  the  outer  part  of  the  semilunar 
ganglion  and  from  the  solar  plexus,  a few  filaments  being  added  from 
the  diaphragmatic  nerve.  They  are  short,  but  numerous  in  compari- 
son with  the  size  of  the  body  which  they  supply;  and  they  enter  the 
upper  and  inner  parts  of  the  suprarenal  capsule.  These  nerves  are 
continuous  below  with  the  renal  plexus.  The  plexus  is  joined  by 
branches  from  one  of  the  splanchnic  nerves,  and  presents  a ganglion 
{gangl.  splanchnico-suprarenale)  where  it  is  connected  with  those 
branches.  The  plexus  and  ganglion  are  smaller  on  the  left  than  on 
the  right  side. 

Eenal  Plexus. 

The  nerves  forming  the  renal  plexus,  which  are  about  fifteen  or 
tw'enty  in  number,  emanate  for  the  most  part,  like  the  preceding 
nerves,  from  the  outer  part  of  the  semilunar  ganglion  ; but  some  are 
added  from  the  solar  plexus  and  the  aortic  plexus.  Moreover,  fila- 
ment's of  the  smallest  splanchnic  nerve,  and  occasionally  from  the 
other  splanchnic  nerves,  terminate  in  the  renal  plexus.  As  they  fol- 
low onwards  the  renal  artery,  ganglia  of  ditferent  sizes  are  formed  on 
these  nerves.  Lastly,  dividing  with  the  divisions  of  the  vessel,  the 
nerves  follow  the  vessels  into  the  substance  of  the  kidney.  On  the 
right  side  some  filaments  are.  furnished  to  the  vena  cava,  behind 
which  the  plexus  passes  with  the  renal  artery,  and  others  go  to  form 
the  spermatic  plexus. 

Spermatic  Plexus. 

This  small  plexus  commences  in  the  renal  plexus,  but  receives  in  its 
progress  with  the  spermatic  artery  an  accession  from  the  aortic 
plexus.  Continuing  downwards  to  the  testis,  the  spermatic  nerves 
are  connected  with  others,  which  accompany  the  vas  deferens  and  its 
artery  from  the, pel  vis. 


352 


SUPERIOR  MESENTERIC  PLEXUS. 


In  the  female,  the  plexus,  like  the  artery,  is  distributed  to  the  ovary 
and  the  uterus. 

Cceliac  Plexus,  and  its  subdivisions. 

The  cceliac  plexus  is  of  large  size,  and  is  derived  from  the  fore  part 
of  the  great  epigastric  plexus.  It  surrounds  the  cceliac  axis  in  a kind 
of  membranous  sheath,  and  subdivides,  as  the  artery,  into  coronary, 
hepatic,  and  splenic  plexuses.  The  plexus  receives  offsets  from  one 
or  more  of  the  splanchnic  nerves,  and  on  the  left  side  a branch  from 
the  pneumogastric  nerve  is  continued  into  it  (Swan). 

a.  The  coronary  plexus  is  placed  with  its  artery  along  the  small 
curvature  of  the  stomach,  and  unites  with  the  nerves  which  accom- 
pany the  pyloric  artery,  as  well  as  with  branches  of  the  pneumogastric 
nerves.  The  nerves  of  this  plexus  enter  the  coats  of  the  stomach,  after 
lying  a short  distance  beneath  the  peritoneum. 

b.  The  hepatic  plexus,  the  largest  of  the  three  divisions  of  the  cceliac 
plexus,  ascends  with  the  hepatic  vessels  and  the  bile-duct,  and,  entering 
the  substance  of  the  liver,  ramifies  on  the  branches  of  the  vena  portae 
and  the  hepatic  artery.  Offsets  from  the  left  pneumogastric  and 
from  the  diaphragmatic  nerves  join  the  hepatic  nerves  at  the  left  side 
of  the  hepatic  vessels.  From  this  plexus  are  furnished  filaments  to  the 
right  suprarenal  plexus,  as  well  as  other  secondary  plexuses  which 
follow  branches  of  the  hepatic  artery.  Thus  there  is  with  the  pyloric 
artery  a pyloric  plexus,  which  gives  branches  on  the  small  curvature 
of  the  stomach,  and  is  connected  with  the  pneumogastric  nerves,  as 
well  as  with  the  plexus  on  the  coronary  artery.  Again,  a gastro-epi- 
ploiic  and  a gastro-duodenal  plexus  are  furnished  from  the  hepatic 
plexus.  The  former  surrounds  the  right  gastro-epiploi'c  artery,  and 
communicates  with  the  nerves  from  the  splenic  plexus,  which  lie  on 
the  left  gastro-epiploic  vessel;  while  the  gastro-duodenal  plexus  sup- 
plies the  duodenum  and  the  pancreas,  and  joins  the  mesenteric  plexus. 
The  plexuses  just  noticed  supply  filaments  to  the  stomach,  chiefly  at 
its  pyloric  end.  Near  the  liver  the  cystic  plexus  is  derived  from  the 
same  source  as  the  nerves  last  described,  and  is  conveyed  to  the  gall- 
bladder by  the  cystic  artery. 

c.  The  splenic  plexus  is  continued  on  the  splenic  artery  and  its  divi- 
sions into  the  substance  of  the  spleen.  This  plexus  is  reinforced  at  its 
beginning  by  branches  from  the  left  semilunar  ganglion,  and  by  a fila- 
ment from  the  right  vagus  nerve.  It  furnishes  the  left  gastro-epiploic 
and  pancreatic  plexuses,  which  course  along  the  branches  of  the 
splenic  artery  bearing  the  same  appellation,  and,  like  the  vessels,  are 
distributed  to  the  stomach  and  pancreas. 

Superior  Mesenteric  Plexus. 

The  plexus  accompanying  the  superior  mesenteric  artery,  whiter  in 
colour  and  firmer  than  either  of  the  preceding  offsets  of  the  solar 
plexus,  envelopes  the  artery  in  a membraniform  tube,  and  receives  a 
prolongation  from  the  junction  of  the  right  pneumogastric  nerve  with 
the  cceliac  plexus.  About  the  root  of  the  artery,  ganglionic  masses 
(gangl.  meseraica)  occur  in  connexion  with  the  nerves  of  this  plexus. 


INFERIOR  MESENTERIC  PLEXUS. 


353 


The  offsets  of  the  plexus  are  in  name  and  number  the  same  as  the 
vessels;  and,  in  the  same  manner  as  the  vessels,  they  supply  the 
greater  part  of  the  small  intestines,  viz.,  the  jejunum  and  ileum,  as  well 
as  the  ascending  and  the  transverse  colon.  The  pancreas  also  re- 
ceives nerves  from  the  superior  mesenteric  plexus.  The  nerves  are 
distributed  as  follows  : — 

Closely  encircling  the  superior  mesenteric  artery,  the  plexus  enters 
with  that  vessel  between  the  layers  of  the  mesentery,  and  furnishes 
secondary  plexuses  around  the  branches  of  the  artery : viz.,  intestinal 
nerves  to  the  small  intestine,  and  plexuses  for  the  supply  of  the  large 
intestine,  named  severally  ileo-colic,  right  colic,  and  middle  colic.  In 
their  progress  to  the  intestine  some  nerves  quit  the  arteries  which  first 
supported  them,  and  are  directed  forwards  in  the  intervals  between 
the  vessels.  As  they  proceed,  they  divide,  and  unite  with  lateral 
branches,  like  the  arteries,  but  without  the  same  regularity;  and  they 
enter  the  intestine  where  the  mesentery  is  connected  with  it.  The 
highest  of  the  foregoing  nerves,  those  on  the  jejunum,  communicate 
with  the  gastro-duodenal  plexus;  and  those  distributed  to  the  trans- 
verse colon  (middle  colic  nerves)  join  with  the  left  colic  nerves  fur- 
nished from  the  inferior  mesenteric  plexus. 

The  Aortic  Plexus. 

The  aortic  or  inter-mesenteric  plexus  is  placed  along  the  abdominal 
aorta,  and  occupies  the  interval  between  the  origin  of  the  superior  and 
inferior  mesenteric  arteries.  This  plexus  may  be  considered  a pro- 
longation of  the  solar  plexus,  which  supplies  nerves  to  accompany 
some  of  the  lower  branches  of  the  aorta.  Above,  it  consists,  for  the 
most  part,  of  two  lateral  portions,  (connected  with  the  semilunar  gan- 
glia and  renal  plexuses,)  which  are  extended  on  the  sides  of  the  aorta, 
but  with  communicating  branches  over  that  vessel.  It  is  joined, 
moreover,  by  branches  of  some  of  the  lumbar  ganglia. 

The  aortic  plexus  furnishes  the  inferior  mesenteric  plexus  and  part 
of  the  spermatic,  gives  some  filaments  to  the  lower  vena  cava,  and 
ends  in  the  hypogastric  plexus. 

Inferior  Mesenteric  Plexus. 

The  inferior  mesenteric  plexus  is  derived  principally  from  the  left 
lateral  part  of  the  aortic  plexus,  and  closely  surrounds  with  a network 
the  inferior  mesenteric  artery.  It  distributes  nerves  to  the  left  or 
descending  part,  and  the  sigmoid  flexure  of  the  colon,  and  assists  in 
supplying  the  rectum.  The  nerves  of  this  plexus,  like  those  of  the 
superior  mesenteric  plexus,  are  firm  in  texture,  and  whitish  in  colour. 

As  it  proceeds  along  the  artery,  the  inferior  mesenteric  plexus 
divides  into  the  following  secondary  plexuses,  viz.,  left  colic,  sigmoid, 
and  superior  hcemorrhoidal,  which  surround  respectively  the  branches 
of  the  artery.  In  their  progress  to  the  intestine,  the  nerves  of  these 
plexuses  subdivide,  and  join,  like  the  branches  of  the  superior  mesen- 
teric nerves : the  highest  branches  (those  on  the  left  colic  artery)  are 
connected  with  the  last  branches  (middle  colic)  of  the  superior  mesen- 

30* 


354 


INFERIOR  H.®MORRHOIDAL  NERVES. 


teric  plexus,  while  others  in  the  pelvis  unite  with  offsets  from  the  infe- 
rior hypogastric  plexus  of  the  left  sidei 

3.  HYPOGASTRIC  PLEXUS. 

The  hypogastric  plexus  (plexus  hypogastricus  superior,  seu  uterinus 
communis — Tiedemann  ; plex.  hypogastr.  medius  seu  impar — Muller; 
inferior  aortic  plexus),  the  prevertebral  assemblage  of  nerves  destined 
for  the  supply  of  the  viscera  of  the  pelvis,  lies  invested  in  dense  cellu- 
lar membrane,  in  the  interval  between  the  two  common  iliac  arteries. 
The  nerves  from  which  it  is  formed,  about  twelve  in  number  on  each 
side,  descend  from  the  aortic  plexus,  receiving  filaments  from  the  lum- 
bar ganglia,  and,  after  crossing  the  common  iliac  artery,  form  an 
interlacement  with  as  many  nerves  from  the  opposite  side.  The 
plexus  contains  no  ganglia.  At  the  lower  end  it  divides  into  two 
parts,  which  are  directed  forward,  one  to  each  side  of  the  pelvic 
viscera. 

Inferior  Hypogastric  Plexuses. 

Inferior  hypogastric  plexus  (plexus  gangliosus  inferior;  hypogastricus 
lateralis  inferior — Tiedemann  ; plexus  hypogastricus  inferior — Muller; 
pelvic  plexus — Beck).  Each  of  the  two  prolongations  of  the  hypo- 
gastric plexus  is  continued  forward  by  the  side  of  the  rectum,  its 
branches  entering  into  repeated  communications  as  they  descend,  and 
forming  at  the  points  of  connexion  small  knots,  which  contain  a little 
ganglionic  matter.  After  descending  some  way,  they  become  united 
with  branches  of  the  spinal  nerves,  as  well  as  with  a few  offsets  of  the 
sacral  ganglia,  and  the  union  of  all  constitutes  the  inferior  hypogastric 
plexus.  The  spinal  branches,  which  enter  into  the  plexus,  are  furnished 
from  the  third  and  fourth  sacral  nerves  (in  greatest  number  by  the 
former  of  these) ; a couple  of  filaments  being  likewise  added  from  the 
second  sacral  nerve.  Small  ganglia  are  formed  at  the  place  of  union 
of  the  nerves,  as  well  as  elsewhere  in  the  plexus  (plexus  gangliosus — 
Tiedemann). 

From  the  plexus  so  constituted  numerous  nerves  are  distributed  to 
the  pelvic  viscera.  They  correspond  with  the  branches  of  the  internal 
iliac  artery,  and  of  course  vary  with  the  sex;  thus,  besides  hsemor- 
rhoidal  and  vesical  nerves,  which  are  common  to  both  sexes,  there  are 
nerves  special  to  each,  namely,  those  destined,  in  the  male,  for  the 
prostate,  vesicula  seminalis,  and  vas  deferens ; in  the  female,  for  the 
vagina,  uterus,  ovary,  and  Fallopian  tube. 

The  nerves  distributed  to  the  urinary  bladder  and  the  vagina  contain 
a larger  proportion  of  spinal  nerves  than  those  furnished  to  the  other 
pelvic  viscera. — The  offsets  of  the  inferior  hypogastric  plexus  will  now 
be  noticed  separately. 

Inferior  Haemorrhoidal  Nerves. 

These  slender  nerves  pass  away  from  the  back  part  of  the  inferior 
hypogastric  plexus.  They  join  with  the  nerves  (superior  hasmor- 
rhoidal)  which  descend  from  the  abdomen  with  the  inferior  mesenteric 
artery,  and  penetrate  the  coats  of  the  rectum. 


NERVES  OF  THE  OVARY. 


355 


Vesical  Plexus. 

The  nerves  of  the  urinary  bladder  are  very  numerous.  They  are 
directed  from  the  anterior  part  of  the  inferior  hypogastric  plexus  to 
the  side  and  lower  part  of  the  bladder.  At  first,  these  nerves  accom- 
pany the  vesical  blood-vessels,  but  afterwards  they  leave  the  vessels, 
and  subdivide  into  minute  fibrils,  before  perforating  the  muscular 
coat  of  the  organ.  From  the  vesical  plexus,  nerves,  or  what  may  be 
considered  secondary  plexuses,  are  given  in  the  male  to  the  vas 
deferens  and  the  vesicula  seminalis. 

a.  The  nerves  of  the  vas  deferens  ramify  around  that  tube,  and 
communicate  in  the  spermatic  cord  with  the  nerves  of  the  spermatic 
plexus,  b.  Those  furnished  to  the  vesicula  seminalis  form  an  inter- 
lacement on  the  vesicula,  and  some  branches  penetrate  its  substance. 
Other  filaments  from  the  prostatic  nerves  reach  the  same  structure. 

Prostatic  Plexus. 

This  plexus  is  continued  from  the  lower  part  of  the  inferior  hypo- 
gastric plexus.  The  nerves  are  of  considerable  size,  and  pass  onwards 
between  the  prostate  and  the  levator  ani.  Some  are  furnished  to  the 
gland  (from  which  they  are  named),  and  to  the  vesicula  seminalis ; 
and  the  plexus  is  then  continued  forward  to  supply  the  erectile  sub- 
stance of  the  penis,  where  the  nerves  al’e  named  “ cavernous.” 

Cavernous  nerves  (of  the  penis).* — These  are  very  slender,  and 
difficult  to  dissect.  Continuing  from  the  prostatic  plexus,  at  the  fore 
part  of  the  prostate  gland,  they  pass  onwards  beneath  the  arch  of  the 
pubes,  and  through  the  muscular  structure  connected  with  the  mem- 
branous part  of  the  urethra,  to  the  dorsum  of  the  penis.  At  the  ante- 
rior margin  of  the  levator  ani  muscle  some  short  filaments  from  the 
pudic  nerve  join  the  cavernous  nerves.  After  distributing  twigs  to  the 
prostate  at  its  fore  part,  these  nerves  divide  into  branches  for  the 
erectile  substance  of  the  penis,  as  follows : 

a.  Small  cavernous  nerves  (nervi  cavemosi  minores — Miiller),  which  perforate  the 
fibrous  covering  of  the  corpus  cavernosum  near  the  root  of  the  penis,  and  end  in 
the  erectile  substance. 

b.  The  large  cavernous  nerve  (n.  cavernosus  major),  which  extends  forward  on 
the  dorsum  of  the  penis,  and  dividing,  gives  filaments  that  penetrate  the  corpus 
cavernosum,  passing  with  or  near  the  cavernous  artery  (art.  profunda  penis).  As 
it  continues  onwards,  this  nerve  joins  with  the  dorsal  branch  of  the  pudic  nerve, 
about  the  middle  of  the  penis,  and  is  distributed  to  the  corpus  cavernosum. 
Branches  from  the  foregoing  nerves  reach  the  corpus  spongiosum  urethrae. 

The  remaining  nerves  are  peculiar  to  the  female. 

Nerves  of  the  Ovary. 

The  ovary  is  supplied  chiefly  from  the  plexus  prolonged  on  the 
ovarian  artery  from  the  abdomen  ; but  it  receives  another  offset  from 
the  uterine  nerves. 

* These  nerves  have  been  made  the  subject  of  a monograph  by  Professor  Muller ; it  is 
entitled  “Ueber  die  Organischen  Nerven  der  erectilen  mannlichen  Geschlechts-organe,” 
&c.  Berlin,  1836. 


356 


UTERINE  NERVES. 


Vaginal  Plexus. 

The  nerves  furnished  lo  the  vagina  leave  the  lower  part  of  the  infe- 
rior hypogastric  plexus — that  part  with  which  the  spinal  nerves  are 
more  particularly  combined.  They  are  distributed  to  the  vagina 
without  previously  entering  into  a plexiform  arrangement ; and  they 
end  in  the  erectile  tissue,  on  its  lower  and  anterior  part. 

Nerves  of  the  Uterus. 

These  nerves  are  given  from  the  upper  part  of  the  inferior  hypo- 
gastric plexus — more  immediately  from  the  lateral  fasciculus  prolonged 
to  this  plexus  from  the  hypogastric  plexus,  above  the  point  of  connexion 
with  the  sacral  nerves.  Separating  from  the  plexus  opposite  the  neck 
of  the  uterus,  they  are  directed  upwards  with  the  blood-vessels  along 
the  side  of  this  organ,  between  the  layers  of  its  broad  ligament.  The 
larger  part  of  the  nerves  soon  leave  the  vessels,  and  after  dividing 
repeatedly,  (but  without  communicating  one  with  the  other,  and  with- 
out forming  any  gangliform  enlargements,)  sink,  into  the  substance  of 
the  uterus,  penetrating,  for  the  most  part,  its  neck  and  the  lower  part 
of  its  body.  One  branch,  continuing  directly  from  the  common  hypo- 
gastric plexus,  reaches  the  body  of  the  uterus  above  the  rest;  and  a 
nerve  from  the  same  source  ascends  to  the  Fallopian  tube.  Some 
very  slender  filaments  are  differently  disposed  from  the  preceding 
nerves:  these  form  a plexus  round  the  arteries,  and  terminate  on  or 
with  those  vessels.  On  the  last-mentioned  plexiform  vascular  branches 
minute  ganglia  are  formed  at  intervals.  Lastly,  the  fundus  of  the 
uterus  often  receives  a branch  from  the  ovarian  nerve.*  (See  Mr. 
Beck’s  paper,  especially  the  plate  marked  12.) 

The  nerves  of  the  gravid  uterus. — The  recent  dissections  of  Mr. 
Beck  (if,  as  they  seem  to  be,  accurate)  prove  that  the  nerves  do  not 
alter  in  their  thickness  during  pregnancy,  at  least,  that  no  alteration 
occurs  before  they  enter  the  tissue  of  the  uterus;  while  that  organ 
itself,  and  the  vessels  which  supply  it,  undergo  a remarkable  augmen- 
tation in  size. 

It  is  doubtless  owing  to  the  great  difficulty  of  dissecting  the  uterine  nerves, 
mixed  up  as  they  are  with  arteries,  veins,  and  lymphatics,  together  with  laminated 
cellular  membrane,  and,  as  a result  of  this  difficulty,  to  the  want  of  adequate  dis- 
sections, that  anatomists  have  come  to  opposite  conclusions  respecting  the  state 
of  the  nerves  in  the  circumstances  indicated  in  the  last  paragraph ; some,  as 

* From  tlie  preceding  statement  it  may  be  inferred  that  the  uterus  does  not  receive  any 
considerable  supply  of  nerves.  It  is  necessary,  however,  to  mention,  that  Dr.  Robert  Lee 
has  described  and  given  representations  of  a large  additional  system  of  uterine  nerves  not 
previously  noticed  by  any  anatomist,  at  least  not  noticed  as  nervous  structures ; and  the 
observations  of  this  inquirer,  if  correct,  would  prove  that  the  uterus  is  supplied  with  nerves 
in  great  abundance, — that  it  is  in  fact  to  a considerable  extent  covered  with  a stratum  of 
nervous  plexuses  and  ganglia. 

The  editor  has  not  embodied  the  statements  peculiar  to  Dr.  Lee  with  the  account  of  the 
uterine  nerves  contained  in  this  work,  in  consequence  of  having  come  to  the  conclusion, 
from  his  own  examination  of  the  subject,  that  Dr.  Lee  has  been  mistaken  with  respect  to 
the  nature  of  the  structure  he  has  been  the  first  to  describe  as  nerve — namely,  the  layer  of 
fibres  lying  immediately  under  the  peritoneum  in  the  form  of  “a  great  web,”  and  extending 
over  a large  part  of  the  uterus. — For  the  details  of  the  researches  here  adverted  to,  see 
“ The  Anatomy  of  the  Nerves  of  the  Uterus,”  by  Robt.  Lee,  M.D.,  F.R.S.,  London,  Baillibre, 
1841 ; and  two  papers  by  the  same  author  in  the  “Philosophical  Transactions”  for  1842. 


UTERINE  NERVES. 


357 


William  Hunter,  Professor  Tiedemann,  and  Dr.  Lee,  stating  that  the  nerves  are 
enlarged  in  the  gravid  uterus ; while  others,  including  John  Hunter,  maintained 
the  opposite  opinion.  With  respect  to  the  researches  of  Mr.  Beck  referred  to  in 
the  text : the  representations  of  the  gravid  uterus  and  of  the  imimpregnated  uterus 
of  a person  who  had  home  children,  which  are  contained  in  his  paper,  show  the 
nervous  fibrils  to  be  of  the  same  size  in  both  cases ; and  the  author  (it  is  stated 
in  a note,  page  222,)  has  ascertained  by  another  dissection,  that  no  difference  in 
thickness  is  perceptible  between  the  nerves  of  the  virgin  uterus  and  those  just 
alluded  to. 


ORGANS  OF  THE  SENSES. 


THE  EYE. 

Besides  the  several  structures  which  compose  the  globe  of  the  eye, 
and  constitute  it  an  optical  instrument,  there  are  certain  external 
accessory  parts  which  protect  that  organ,  and  are  intimately  con- 
nected with  the  proper  performance  of  its  functions.  These  are 
known  as  the  “appendages  of  the  eye,”  (they  have  been  named  like- 
wise tutamina  oculi) ; and  they  include  the  eyebrows,  the  eyelids,  the 
organs  for  secreting  the  sebaceous  matter,  and  the  tears,  together 
with  the  canals  by  which  the  latter  fluid  is  conveyed  to  the  nose. 
The  orbits  in  which  the  eyes  are  lodged  have  been  already  described 
(ante,  vol.  i.  p.  159). 

A.  APPENDAGES  OF  THE  EYE. 

1.  THE  EYEBROWS. 

The  eyebrows  (supercilia)  are  arched  ridges,  surmounting  on  each 
side  the  upper  border  of  the  orbit,  and  forming  a boundary  between 
the  forehead  and  the  upper  eyelid.  They  consist  of  thick  integument, 
studded  with  stiff,  obliquely  set  hairs,  under  which  lies  some  fat,  with 
part  of  the  orbicularis  palpebrarum  and  the  corrugatof  supercilii 
muscles.  By  the  last-named  muscle  and  the  occipito-frontalis  the 
brows  are  moved  in  opposite  directions,  to  influence  the  admission  of 
light  to  the  eye,  and  in  the  expression  of  different  passions. 

2.  THE  EYELIDS. 

The  eyelids  (palpebrse)  are  two  thin  movable  folds  placed  in  front 
of  each  eye,  and  calculated  to  conceal  it,  or  leave  it  exposed,  as 
occasion  may  require.  The  upper  lid  is  larger  and  more  movable 
than  the  lower,  and  has  a muscle  (levator  palpebrae  superioris)  exclu- 
sively intended  for  its  elevation.  Descending  below  the  middle  of  the 
eye,  the  upper  lid  covers  the  transparent  part  of  the  organ  ; and  the 
eye  is  opened,  or  rather  the  lids  are  separated,  by  the  elevation  of  the 
upper  one  under  the  influence  of  the  muscle  referred  to.  The  eyelids 
are  joined  at  the  outer  and  inner  angles  {canthi)  of  the  eye;'  the  interval 
between  the  canthi  {fissura  'palpebrarum)  varies  in  length  in  different 
persons,  and,  according  to  its  extent,  (die  size  of  the  globe  being 
nearly  the  same,)  gives  the  appearance  of  a larger  or  a smaller  eye. 
At  the  outer  angle,  which  is  more  acute  than  the  inner,  the  lids  are  in 
close  contact  with  the  eyeball ; but,  at  the  inner  canthus,  the  carun- 
cula  lachrymalis  intervenes.  The  free  margins  of  the  lids  are  straight, 
so  that  they  leave  between  them,  when  approximated,  merel}'’  a trans- 
verse chink.  The  greater  part  of  the  edge  is  flattened,  but  towards 
the  inner  canthus  it  is  rounded  off  for  a short  space ; and,  where  the 


THE  TARSAL  CARTILAGES. 


359 


two  differently  formed  parts  join,  there  exists  on  each  lid  a slight 
conical  elevation  {’papilla  lachrymalis),  the  apex  of  which  is  pierced 
by  the  aperture  (punctum)  of  the  corresponding  lachrymal  duct. 

Structure  of  the  lids. — The  skin  covering  the  eyelids  is  thin  and 
delicate ; and  at  the  line  of  the  eyelashes,  altered  in  its  character, 
joins  the  conjunctival  mucous  membrane  which  lines  the  inner  surface 
of  the  lids  and  is  reflected  over  the  front  of  the  eyeball.  Beneath  the 
skin,  and  in  the  fold  formed  between  it  and  the  conjunctiva,  the  fol- 
lowing structures  are  successively  met  with,  viz. : — a layer  of  fine 
cellular  tissue,  without  fat;  the  fibres  of  the  orbicular  muscle;  a thin 
fibrous  membrane,  attached  round  the  margin  of  the  orbit  to  the  pe- 
riosteum ; the  tarsal  cartilages,  to  which  also  this  fibrous  membrane 
is  connected  ; and  finally  the  Meibomian  glands.  In  the  upper  eyelid 
there  is  (in  addition  to  these  parts,  which  are  common  to  both  lids,) 
an  expansion  from  the  tendon  of  the  levator  palpebrse,  already  noticed: 
it  lies  close  against  the  conjunctiva.  The  structures  now  enumerated 
require  separate  examination. 

The  tarsal  cartilages  (tarsi)  are  two  thin  plates  of  fibro-cartilage, 
placed  one  in  each  lid,  and  serving  to  give  shape  and  firmness  to 
these  parts.  The  upper  cartilage,  the  larger,  is  half  oval  in  form, 
being  broader-  near  the  centre  and  narrowing  towards  the  angles  of 
the  lids ; the  lower  is  thinner,  smaller,  and  more  nearly  of  a uniform 
breadth  throughout.  The  free  or  ciliary  edge  of  the  cartilages,  which 
is  straight,  is  thicker  than  any  other  part.  The  margin  towards  the 
orbit  is  thin,  and  connected  to  the  periosteum  by  means  of  a layer  of 
fibrous  membrane,  which  is  stronger  near  the  outer  canthus  than 
elsewhere,  and  has  been  there  named  the  external  tarsal  ligament. 
The  thin  edge  of  the  upper  cartilage  likewise  receives  the  tendon  of 
the  levator  palpebree  muscle.  Near  the  inner  canthus  the  cartilages 
end  in  fibrous  slips,  which  are  closely  attached  to  the  tendo  palpe- 
brarum (see  vol.  i.  p,  335). 

Meibomian  glands  (glandulse  Meibomii),  fig.  375. — On  the  ocular 
surface  of  each  lid  are 


sefen  from  thirty  to  forty 
parallel  vertical  lines  of 
yellow  granules,  lying  im- 
mediately under  the  con- 
junctival mucous  mem- 
brane. They  are  seba- 
ceous follicles,  embedded 


Fig.  375. 


in 


grooves  at  the  back  of 


the  tarsal  cartilages,  and 
opening  on  the  free  mar- 
gin of  the  lids  by  minute 
orifices,  generally  as  many 
in  number  as  the  lines 

follicles  themselves.  Meibomian  glands  seen  from  the  inner  or  ocular  surface 
These  glands  consist  of  of  the  eyelids,  with  the  lachrymal  gland — the  right  side. — a. 
npnrhr  otrairrlot  c.Yprptr>r\r  Palpebral  conjunctiva.  1.  Lachrymal  gland.  2.  Openings 
Iiedriy  Siraigni  excretory  lachrymal  ducts.  3.  Lachrymal  puncta.  6.  Meibomian 
tubes,  each  oi  which  is  glands, 
closed  at  the  end,  and  has 


360 


LACHRYMAL  CANALS. 


numerous  small,  sessile,  cmcal  appendages  growing  from  its  sides. 
The  tubes  are  lined  by  mucous  membrane,  on  the  surface  of  which  is 
a layer  of  scaly  or  pavement  epithelium  cells. 

The  eyelashes  (cilia)  are  short  curved  hairs,  arranged  in  two  or 
more  row's  along  the  margin  of  the  lids,  just  at  the  line  of  union  be- 
tween the  skin  and  conjunctival  mucous  membrane.  The  lashes  of 
the  upper  lid,  more  numerous  and  longer  than  the  lower,  have  the 
convexity  of  their  curve  directed  downwards  and  forwards;  whilst 
those  of  the  lower  lid  are  arched  in  the  opposite  direction.  Near  the 
inner  canthus  these  hairs  are  weaker  and  more  scattered.  A few 
slender  hairs  grow  likewise  from  the  caruncula  lachrymalis. 

Caruncula  lachrymalis,  fig.  376.  — This  is  a small  red  conical 
body,  occupying  the  inner  angle  of  the  eyelids;  it  consists  of  a group 
of  follicles,  covered  by  mucous  membrane.  The  membrane  on  the 
outer  side  of  the  caruncle  is  formed  into  a semilunar  fold  {plica  semi- 
lunaris), the  concavity  of  w'hich  looks  towards  the  cornea.  The  fol- 
licles secrete  a peculiar  fluid  for  lubricating  the  mucous  surface;  and 
the  semilunar  fold  of  the  membrane  is  considered  as  the  rudiment  of 
the  third  eyelid  (membrana  nictitans)  found  in  some  animals. 

3.  THE  LACHRYMAL  APPARATUS. 

The  assemblage  of  parts  which  constitute  the  lachrymal  apparatus 
are  the  following,  viz.: — the  gland  by  which  the  tears  are  secreted  at 
the  outer  side  of  the  orbit;  the  twm  canals  into  which  the  fluid  is 
received  near  the  inner  canthi ; and  the  sac  with  the  duct  continued 
from  it,  through  which  the  tears  pass  to  the  interior  of  the  nose. 

The  lachrymal  gland,  fig.  375, S is  an  oblong  body,  about  the  size  of 
a small  almond,  placed  in  the  upper  and  outer  part  of  the  orbit,  and 
immediately  behind  its  anterior  margin.  The  upper  surface  of  the 
gland,  convex,  is  lodged  in  a depression  in  the  orbital  plate  of  the 
frontal  bone,  to  the  periosteum  of  which  it  adheres  by  fibrous  bands; 
the  lower  surface  is  adapted  to  the  convexity  of  the  eyeball,  and  is  in 
contact  with  the  upper  and  the  outer  recti  muscles.  The  fore  part  of 
the  gland,  separated  from  the  body  of  the  organ  by  a slight  depression, 
and  sometimes  described  as  a second  lobe,  is  closely  adherent  to  the 
back  of  the  upper  eyelid,  and  is  covered,  on  the  ocular  surface,  only 
bv  a reflection  of  the  conjunctiva.  The  lachrymal  ducts,  usually  eight 
or  ten  in  number,  are  very  small,  and  emerge  from  the  thinner  portion 
of  the  gland.  After  running  obliquely  under  the  mucous  membrane, 
and  separating  at  the  same  time  one  from  the  other,  they  open  by 
separate  orifices,  fig.  375,^  a little  above  the  outer  canthus. 

Lachrymal  canals. — On  the  margin  of  each  lid,  near  the  inner 
angle,  and  in  front  of  the  fold  of  membrane  called  plica  semilunaris, 
is  a small  elevation  (papilla  lachrymalis),  already  described.  Each 
papilla  is  perforated  by  a small  aperture  {punctnm  lachrymale),  fig. 
375,®,  376,’;  and  at  these  apertures  commence  tw'O  small  canals  {cana- 
liculi),  fig.  376,®,  which  convey  the  tears  from  the  eye  to  the  lachrymal 
sac.  The  upper  canal  is  rather  the  smaller  and  longer  of  the  two:  it 
first  ascends  from  the  punctum ; then  makes  a sudden  bend,  and  is 


THE  CONJUNCTIVA. 


361 


[Fig.  376. 


Anterior  view  of  the  Lachrymal  Apparatus. 


directed  inwards  and  downwards 
to  join  the  lachrymal  sac.  The 
lower  canal  descends  from  the 
corresponding  punctum ; and  soon 
changing  its  direction,  as  the  upper 
one,  takes  a nearly  horizontal  course 
inwards.  Both  canals  are  dilated 
where  they  are  bent.  In  some  cases 
they  unite  near  the  end  to  form  a 
short  common  trunk:  more  com- 
monly they  open  separately,  but 
close  together,  into  the  sac. 

The  lachrymal  sac  and  nasal 
duct  together  constitute  the  passage 
by  which  the  ‘tears  are  conveyed 
from  the  lachrymal  canals  to  the 
cavity  of  the  nose.  The  lachrymal 
sac,  fig.  376,^  the  upper  dilated 
portion  of  the  passage,  is  situate  at  At  the  inner  canthus  are  the  puncta,  1,  and 
the  side  of  the  nose,  near  the  inner  Canaliculi,  2.  with  the  caruncula  between  them. 

, , j L j The  lachrymal  sac  forms  the  upper  third  of  the 

canthus  Ol  the  and  lies  embed-  vertical  tube,  5,  6,  and  the  nasal  duct  the  re- 

ded  in  a deep  groove  in  the  ungual  These  pans  are  separated  withi^n  by 

, ^ ‘^•11  I P . a fold  of  the  lining  membrane. — After  Soem- 

and  upper  maxillary  bones.  It  is  merring.] 

of  an  oval  form ; the  upper  end 

closed  and  rounded,  the  lower  end  gradually  narrowing  into  the  nasal 
duct;  on  the  outer  side,  and  a little  in  front,  it  receives  the  lachrymal 
canals.  The  sac  is  composed  of  fibrous  membrane,  adhering  closely 
to  the  bones  above  mentioned,  and  strengthened  by  fibrous  processes 
sent  from  the  tendo  palpebrarum,  which  crosses  a little  above  its  mid- 
dle. The  inner  surface  is  covered  by  a reddish  mucous  membrane, 
which  is  continuous,  through  the  canaliculi,  with  the  conjunctiva,  and 
through  the  nasal  duct  with  the  mucous  membrane  of  the  nose.  The 
sac  is  covered  by  the  tendo  palpebrarum,  and  by  some  of  the  inner 
fibres  of  the  orbicular  muscle  of  the  lids. 

The  nasal  duct  (ductus  ad  nasum),  about  six  or  seven  lines  in  length, 
extends  through  the  upper  maxillary  bone  to  the  fore  part  of  the  lower 
meatus  of  the  nose,  the  osseous  canal  being  completed  by  the  ungual 
and  lower  turbinate  bones.  A tube  of  fibrous  membrane,  continuous 
with  the  lachrymal  sac,  adheres  to  the  parietes  of  this  canal,  and  is 
lined  by  mucous  membrane,  which,  at  the  opening  into  the  nose,  is 
often  arranged  in  the  form  of  an  imperfect  valve.  The  nasal  duct  is 
rather  narrower  in  the  middle  than  at  either  end ; its  direction  is  not 
quite  vertical,  but  inclines  slightly  outwards  and  backwards. 

4.  THE  CONJUNCTIVA. 

The  conjunctiva  is  a mucous  membrane  which  lines  the  ocular  sur- 
face of  the  eyelids,  and  is  reflected  over  the  fore  part  of  the  sclerotic, 
and  the  anterior  surface  of  the  cornea.  Over  each  of  these  several 
parts  it  presents  peculiar  and  distinctive  characters. 

a.  The  ■palpebral  portion  of  the  conjunctiva  is  opaque  and  red,  is  thicker  and 
VOL.  II.  31 


302 


THE  SCLEROTIC. 


more  vascular  than  any  other  part  of  the  membrane,  and  has  on  its  free  surface 
numerous  line  papillae,  freely  supplied  with  nerves  and  covered  with  epithelium. 
At  the  margins  of  the  lids  the  palpebral  conjunctiva  enters  the  ducts  of  the  Mei- 
bomian glands ; through  the  puncta  lachrymalia  it  passes  into  the  canaliculi,  and 
is  continuous  with  the  lining  membrane  of  the  lachrymal  sac;  and  it  is  prolonged 
into  the  orifices  of  the  ducts  of  the  lachrymal  gland.  At  the  inner  canthus  it  is 
folded  to  form  the  plica  semilunaris,  and  covers  the  caruncula  lachrymalis. 

b.  The  sclerotic  portion  of  the  conjunctiva,  changing  its  character  at  the  line  of 
reflection  from  the  eyelids,  becomes  thinner,  and  loses  its  papillary  structure.  It 
is  also  transparent  and  nearly  colourless,  although  generally  marked  by  a few 
scattered  branches  of  blood-vessels.  The  vessels  of  the  sclerotic  portion  are  ar- 
ranged in  two  layers,  which  are  supplied  from  different  sources,  but  anastomose 
freely,  particularly  round  the  margin  of  the  cornea.  Of  these  the  superficial  net- 
work is  derived  from  the  palpebral  and  lachrymal  arteries ; and  the  deep  layer^ 
from  the  muscular  and  anterior  ciliary  branches  of  the  ophthalmic  artery. 

c.  The  corneal  conjunctiva  is  still  thinner  than  the  sclerotic  portion  of  the  mem- 
brane, and  is  still  more  transparent  and  adherent.  Vessels  are  said  to  have  been 
recently  demonstrated*  in  this  part  of  the  conjunctiva  in  the  healthy  eye,  their 
arrangement  being  as  follows  ; — The  vessels  form  by  close  anastomoses  a circle 
around  the  border  of  the  cornea ; and,  from  the  angles  of  union  between  them, 
minute  offsets  pass  towards  the  centre  of  the  cornea,  while  others  arising  in  the 
same  place  insinuate  themselves  between  the  cornea  and  sclerotic,  and  become 
connected  with  the  vessels  of  the  choroid. 

B.  THE  GLOBE  OF  THE  EYE. 

The  globe  or  ball  of  the  eye  is  placed  in  the  fore  part  of  the  orbital 
cavity,  fixed  principally  by  its  connexion  with  the  optic  nerve  behind, 
and  the  muscles  with  the  eyelids  in  front,  but  capable  of  changing  its 
position  within  certain  limits.  The  recti  and  obliqui  muscles  closely 
surround  the  greater  part  of  the  eyeball;  the  lids,  with  the  plica  semi- 
lunaris, and  caruncle,  are  in  contact  with  it  in  front;  and  behind  it  is 
supported  by  a quantity  of  loose  fat.  The  form  of  the  eyeball  is  irre- 
gularly spheroidal ; and,  when  viewed  in  profile,  is  found  to  be  com- 
posed of  segments  of  two  spheres,  of  which  the  anterior  is  the  smaller 
and  more  prominent : hence  the  diameter  taken  from  before  backwards 
exceeds  the  transverse  diameter  by  about  a line.  The  segment  of  the 
larger  sphere  corresponds  to  the  sclerotic  coat,  and  the  portion  of  the 
smaller  sphere  to  the  cornea. 

Except  when  certain  muscles  are  in  action,  the  axes  of  the  eyes  are 
nearly  parallel ; the  optic  nerves  on  the  contrary  diverge  considerably 
from  one  another,  and  consequently  each  nerve  enters  the  correspond- 
ing eye  a little  to  the  inner  or  nasal  side  of  the  axis  of  the  globe. 

The  eyeball  is  composed  of  several  investing  membranes,  concen- 
trically arranged,  and  of  certain  fluid  and  solid  parts  contained  within 
them.  The  membranes,  neither  of  which  forms  a complete  coat  to 
the  eye,  are  the  conjunctiva,  sclerotica,  cornea,  choroid,  iris,  retina, 
membrane  of  the  aqueous  humour,  capsule  of  the  lens,  and  hyaloid 
membrane.  The  parts  enclosed  are  the  aqueous  and  vitreous  humours, 
and  the  crystalline  lens. 

1.  THE  SCLEROTIC. 

The  sclerotic  (cornea  opaca),  one  of  the  most  complete  of  the  tunics 

* By  Professor  Gaddi,  rrotn  the  injection  of  the  body  of  a child  two  years  old.  “ Bullet, 
dclle  Scienze  mediche,”  1844.  Cited  in  Mr.  Paget’s  “ Report  on  the  Progress  of  Human 
Anatomy  and  Physiology,”  1844-45,  part  2,  in  Brit,  and  Foreign  Med.  Review. 


THE  CORNEA. 


363 


of  the  eye,  and  that  on  which  the  nnaintenance  of  the  form  of  the 
organ  chiefly  depends,  is  a strong,  opaque,  unyielding,  fibrous  structure, 
composed  of  bundles  of  strong  white  fibres,  which  interlace  with  one 
another  in  all  directions.  The  membrane  covers  about  four-fifths  of 
the  eyeball,  leaving  a large  opening  in  front,  which  is  occupied  by  the 
transparent  cornea,  and  a smaller  aperture  behind  for  the  entrance  of 
the  optic  nerve.  The  outer  surface  is  white  and  smooth,  except  where 
the  tendons  of  the  recti  and  obliqui  muscles  are  inserted  into  it.  The 
inner  surface  is  of  a light  brown  colour,  and  rough  from  the  presence 
of  a delicate  cellular  tissue  {membrana  fusca),  through  which  branches 
of  the  ciliary  vessels  and  nerves  cross  obliquely.  The  sclerotic  is 
thickest  at  the  back  part  of  the  eye,  and  thinnest  in  front : the  opening 
for  the  optic  nerve  is  somewhat  smaller  at  the  inner  than  on  the  outer 
surface  of  the  sclerotic.  The  fibrous  sheath  of  the  nerve  continued 
from  the  dura  mater  blends  with  the  sclerotic  round  the  margin  of  the 
aperture;  and  the  internal  covering  {neurilemma)  sends  numerous 
membranous  processes  which  cross  the  nerve  in  various  directions. 
In  consequence  of  this  latter  arrangement,  when  the  nerve  is  cut  off 
close  to  the  eyeball,  the  point  of  its  attachment  is  marked  by  a circular 
group  of  pores  {lamina  cribrosa),  in  which  lies  the  soft  nervous  mat- 
ter, readily  removed  by  maceration.* 

2.  THE  CORNEA. 

The  cornea  (cornea  pellucida),  fig.  382,  ^ is  a transparent  structure, 
occupying  the  aperture  left  in  the  fore  part  of  the  sclerotic,  and  form- 
ing about  one-fifth  of  the  surface  of  the  globe  of  the  eye.  It  is  closely 
united  with  the  anterior  mai'gin  of  the  sclerotic,  and  the  disposition  of 
the  two  at  the  place  of  union  varies;  in  one  case  the  cornea  is  over- 
lapped by  the  sclerotic,  while  in  another  it  appears  to  be  received  into 
a groove  in  that  membrane.  The  circumference  of  the  cornea  is  not 
quite  circular  in  form,  the  transverse  being  rather  longer  than  the 
vertical  diameter.  The  anterior  surface  is  more  convex  than  the 
sclerotic,  and  consequently  projects  beyond  it:  the  actual  degree  of 
convexity,  however,  varies  in  different  persons,  and  at  different  periods 
of  life.  It  is  covered  by  the  conjunctiva,  already  described,  fig.  382. 
The  posterior  surface  of  the  cornea  is  concave,  assists  in  bounding  the 
anterior  chamber  of  the  eye,  and  is  lined  by  a very  thin  and  closely 
adherent  film  of  membrane,f  fig.  382,“  which  can  be  traced  no  further 
than  the  margin  of  the  iris. 

The  cornea  is  thicker  than  any  part  of  the  sclerotic  membrane ; and  is  for  the 
most  part  composed  of  soft  and  indistinct  fibres  arranged  in  several  concentric 
strata.  Between  the  layers  is  a fine  cellular  tissue  which  tears  more  readily  than 
the  substance  of  the  cornea  itself,  and  contains  a small  quantity  of  albuminous 
fluid  (liquor  cornea).  When  macerated  in  water,  or  steeped  in  acid,  the  cornea 
becomes  opaque,  with  the  exception  of  a layer  on  the  posterior  surface,  the  elastic 
Comeaux  which  retains  its  transparency  perfectly,  and  appears  to  undergo  no 

* A different  explanation  has  been  given  of  these  appearances.  Some  anatomists  de- 
scribe the  nerve  as  passing  through  a series  of  holes  in  the  sclerotic  itself;  and  the  part  of 
this  membrane  so  perforated  is  known  as  the  lamina  cribrosa. 

t The  thin  membrane  here  alluded  to  is  by  some  considered  as  the  proper  membrane  of 
the  aqueous  humour,  and  by  others  as  a layer  of  epithelium  covering  that  membrane. 

t This  structure  has  been  named  by  Dr.  Jacob  the  “ elastic  cornea.”  By  many  writers 
it  is  considered  as  a thickened  portion  of  the  membrane  of  the  aqueous  humour  (“  capsula 
aquea  cartilaginosa”). 


364 


THE  CHOROID. 


change.  This  layer,  when  separated  from  the  rest  of  the  cornea,  curls  up,  pre- 
sents a peculiarly  bright  and  glistening  appearance,  and  breaks  with  a serai- 
vitreous  fracture.  It  is  covered  on  the  surface  next  the  aqueous  humour  by  the 
thin  membrane  already  noticed. 

3.  THECHOROID. 


The  choroid  tunic  (tunica  vasculosa)  is  a dark  vascular  membrane, 
lying  between  the  sclerotic  and  the  retina.  Pierced  behind  by  the 
optic  nerve,  it  extends  from  this  point  to  the  ciliary  ligament  and  to 
the  fore  part  of  the  hyaloid  membrane,  where  it  is  thrown  into  folds 
round  the  margin  of  the  crystalline  lens.  The  outer  surface,  nearly 
black  in  colour,  is  loosely  connected  with  the  sclerotic  by  a layer  of 
cellular  tissue,  already  described,  in  which  are  contained  the  ciliary 
nerves  and  the  long  ciliary  arteries  and  veins ; but  these,  being  des- 
tined for  the  supply  of  the  iris,  form  no  part  of  the  choroid.  The 
inner  surface  of  the  choroid  is  soft  and  villous,  highly  vascular,  and  of 
a deep  brown  or  black  colour.  In  front  it  is  attached  to  the  mem- 
brane of  the  vitreous  humour  by  means  of  the  ciliary  processes ; else- 
where it  is  but  loosely  connected  with  the  outer  surface  of  the  retina, 
— the  part  named  Jacob’s  membrane. 

The  choroid  is  composed  of  minute  ramifications  of  arteries  and 
veins,  united  by  cellular  membrane,  and  covered,  particularly  on  the 
inner  surface,  by  a dark  brown  pigment. 


a.  The  veins  of  the  choroid,  fig.  377,  constitute  an  outer  layer,  partially  separable 
from  the  arterial  network,  and  easily  recognised  by  the  direction  of  the  larger 
vessels.  These  converge  to  four  nearly  equidistant  trunks,  377,';  which  pass 
through  the  sclerotic  about  half-way  between  the  margin  of  the  cornea  and  the 

entrance  of  the  optic  nerve,  and 
Fig.  377.  pour  their  contents  into  the  oph- 

thalmic vein.  From  their  whirl- 
like arrangement  they  are  known 
as  vasa  vorticosa. 

h.  The  arteries  of  the  choroid 
are  furnished  by  the  short  ciliary 
branches  of  the  ophthalmic,  fig. 
379,',  which  pierce  the  sclerotic 
close  to  the  optic  nerve,  and 
divide  into  branches  arranged 
parallel  to  the  axis  of  the  eye- 
ball. Communicating  freely, 
they  form  a network  (tumca 
Ruyschiana)  on  the  inner  or  con- 
cave surface  of  the  venous  layer 
just  described,  from  which  they 
may  be  distinguished  by  their 
, smaller  size,  their  more  parallel 
A dissection  of  the  eyeball,  showing  Us  second  tunic  arrnno'Pmpnt  and  their  closer 
and  the  mode  of  distribution  of  the  vasa  vorticosa  of  the  arrarigement,  anU  tueir  Closer 
choroid.  After  Arnold.  1.  Part  of  the  sclerotic  coat.  2.  und  finer  cqmrnunmations.  Ihe 
The  optic  nerve.  3,  3.  The  choroid  coat.  4.  The  ciliary  ultimate  distribution  of  both 
ligament.  5.  The  iris.  6,  6.  The  vasa  vorticosa.  7,  7.  arteries  and  veins  is  at  the  inner 
The  trunks  of  the  vasa  vorticosa  at  the  point  where  they  surface  of  the  choroid 

have  pierced  the  sclerotica.  8,8.  The  posterior  ciliary  d 

veins,  which  enter  the  eyeball  in  company  with  the  pos-  great  vasculanty  of 
terior  ciliary  arteries,  by  piercing  the  sclerotic  at  9.  10.  Ujny  be  shown  by  injecting 

One  of  the  long  ciliary  nerves,  accompanied  by  a long  either  set  of  vessels, 
ciliary  vein.  c The  pigment  (pigmentum 

nigrum  v.  fuscum)^  of  a deep 
brown,  almost  black  colour,  tiiiges  the  outer  surface  of  the  choroid,  as  before 


CILIA RV  PROCESSES. 


365 


said ; but  is  much  more  abundant  on  the  inner  surface  of  that  tunic,  where  it 
forms  a continuous  layer,  which  increases  in  thickness  as  it  approaches  the  fore 
part  of  the  eye.  It  is  covered  by,  and  contained  in  a membrane  of  peculiar 
structure  {membrane  of  the  pigment) ; and  is  composed  of  flat,  hexagonal  cells, 
about  the  1000th  of  an  inch  in  diameter,  each  cell  presenting  the  appearance  of 
a central  transparent  point  {nucleus)^  surrounded  by  a black  margin.  In  albinoes 
the  colouring  matter  is  deficient ; but  a central  nucleus  is  still  visible. 


4.  THE  ANNULUS  ALBIDUS.  (ciLIARY  LIGAMENT.) 

Annulus  albidus  (annulus  cellulosus — Zinn  ; ligamentum  ciliare  — 
Winslow),  fig.  379,  382. — This  is  a flat,  circular,  narrow  band  of 
grayish-white  substance,  lying  under  the  fore  part  of  the  sclerotic, 
close  behind  the  junction  of  that  tunic  with  the  cornea,  and  serving  to 
connect  together  several  structures  in  its  vicinity.  In  a transverse 
section,  this  band  presents  a wedge-like  form.  The  thicker  margin, 
directed  forwards,  assists  in  bounding  the  cavity  of  the  aqueous 
humour,  and  gives  attachment  to  the  circumference  of  the  iris;  the 
posterior  or  thinner  margin  of  the  band  is  continuous  with  the  fore 
part  of  the  choroid,  though  it  differs  obviously  from  that  membrane  in 
being  destitute  of  pigment,  and  much  less  freely  supplied  with  vessels. 
The  greater  part  of  the  outer  surface  of  the  annulus  albidus  is  only 
loosely  connected  to  the  sclerotic  by  cellular  membrane;  but,  just 
behind  the  margin  of  the  cornea,  a firmer  union  is  effected  by  means  of 
a narrow  ring  of  tough  white  fibres,  to  which  the  term  ciliary  ligament 
is  sometimes  more  particularly  applied.  (Krause.)  In  this  situation, 
and  between  the  annulus,  the  cornea,  and  the  sclerotic,  is  inclosed  a 
small  circular  canal,  named  the  canal  of  Fontana,  or  sinus  circularis 
iridis,  fig.  382.  The  inner  portion  of  the  annulus,  less  distinctly 
fibrous,  is  connected  with  the  ciliary  processes,  and  is  traversed  by 
numerous  branches  of  the  cilia_ry  nerves,  which  divide  and  communi- 
cate with  each  other  in  its  substance  before  entering  the  iris. 


5.  CILIARY  PROCESSES.  (cORPUS  CILIARE.) 


Whilst  the  outer  cellular  layer  of  [Fig.  378. 

the  choroid  appears  to  blend  wiih 
the  thin  portion  of  the  annulus  cellu- 
losus, the  vascular  elements  of  the 
tunic,  with  the  pigment  in  large 
quantity,  extend  inwards  behind  the 
iris  and  in  front  of  the  vitreous 
humour.  Approaching  the  margin  of 
the  crystalline  lens,  this  prolonga- 
tion of  membrane  is  thrown  into 
about  60  or  70  radiated  folds  {ciliary 
processes),  the  aggregate  of  which 
is  called  the  corpus  ciliare,  fig. 

378,k  The  folds  or  processes,  al- 
ternately long  and  short,  are  highly  of  the  globe  of  ihe  eye,  seen  from  within.  1. 
vascular,  and  of  a deep  brown  or  T*’®  three  mnics;  scler^ 

1 1 , , -n  1 -iL  nc,  choroid  (the  dark  layer),  and  retina.  2. 

black  colour.  Kach  ciliary  process  The  pupil.  3.  The  iris,  the  surface  presented 

is  broad  and  flattened  behind  (pars  12, section  being  the  uvea,  4. 
„ 7-  . , ' 1 he  ciliary  processes.  5.  The  scalloped  ante- 

Uon  pllCCltd)^  fig.  378  5 but  is  nar-  rior  border  of  the  retina. — W.] 

31* 


The  anterior  segment  of  a transverse  section 


366 


THE  IRIS. 


rower  and  more  prominent  in  front  {-pars  plicata),  fig.  378,  where  it 
projects  into  the  posterior  chamber,  and  digitates  with  somewhat 
similar  radiated  folds  {zonula  Zinnii),  attached  to  the  fore  part  of  the 
membrane  of  the  vitreous  humour.  A sinuous  or  dentated  line  {ora 
serrata)  marks  the  commencement  of  the  flat  portion  of  the  corpus 
ciliare  from  the  anterior  end  of  the  choroid  membrane. 

The  blood-vessels  of  the  ciliary  processes  are  very  numerous,  and  are  derived  from 
the  fore  part  of  the  choroid  membrane.  At  the  ora  serrata  several  small  arterial 
branches  enter  each  ciliary  process,  at  first  nnming  parallel  to  each  other  and 
communicating  sparingly.  As  they  enter  the  prominent  folded  portion  {pars pli- 
cata), these  vessels  become  tortuous,  subdivide  minutely,  and  inosculate  fre- 
quently by  cross  branches.  Finally  they  form  short  arches  or  loops,  and  turn 
backwards  to  pour  their  contents  into  the  radicles  of  the  veins. 

On  the  free  border  of  the  fold,  one  artery,  larger  than  the  rest,  extends  the 
w'hole  length  of  each  ciliary  process,  and  communicates  with  a longvenous  trunk 
which  runs  a similar  course  on  the  attached  surface. 

6.  T H E I R I s. 

The  iris,  fig.  378,  is  a thin,  flat,  membranous  septum,  perforated 
near  the  centre  by  a circular  aperture  (the  pupil).  Hanging  verti- 
cally in  the  aqueous  humour,  it  divides  unequally  the  space  between 
the  cornea  and  the  crystalline  lens.  The  outer  or  larger  border  of  the 
iris  is  attached  to  the  annulus  albidus,  immediately  behind  the  margin 
of  the  cornea,  and  in  front  of  the  ciliary  processes ; the  inner  edge 
corresponds  to  the  aperture  of  the  pupil,  and  moves  freely  in  the 
aqueous  humour.  The  pupil,  the  circular  aperture  already  referred 
to,  is  situate  a little  to  the  inner  or  nasal  side  of  the  centre  of  the  iris, 
and  varies  in  size  according  to  the  state  of  contraction  or  dilatation  of 
the  fibres  of  which  that  structure  is  composed. 

On  the  anterior  surface  the  iris  is  marked  by  radiating  lines,  and  is 
differently  coloured  in  different  persons ; the  tinge  being  usually  some- 
what deeper  round  the  pupil  than  elsewhere.  Closely  examined,  it 
presents,  about  midway  between  its  borders,  numerous  small  irregular 
elevations,  from  which  little  ridges  or  bands  converge  towards  the 
centre  of  the  pupil.  The  posterior  surface  of  the  iris  itself  is  colour- 
less, but  is  hidden  by  a quantity  of  black  pigment  contained  under  a 
thin  transparent  membrane  (waea),  similar  in  structure  to  that  already 
described  in  the  choroid,  except  that  the  cells  composing  it  are  not 
quite  so  accurately  formed  and  regularly  arranged.  This  surface  is 
also  marked  by  lines  extending  betvveen  the  pupillary  and  the  ciliary 
margins,  which  correspond  to  radiating  bands:  they  are  seen  more 
distinctly  after  the  removal  of  the  uvea. 

Structure. — The  iris  contains  radiating  and  circular  fibres,  which, 
though  in  man  presenting  no  transverse  markings,  are  universally 
admitted  to  be  muscular  in  their  nature.  The  - radiating  fibres  are 
most  distinct  near  the  larger  margin  ; they  arise,  in  front  of  the  circu- 
lar fibres,  from  the  corneal  edge  of  the  annulus  albidus,  and  are 
covered  at  this  point  by  a reflection  of  the  fine  membrane  that  lines 
the  concave  surface  of  the  cornea.  They  converge  towards  the 
pupil,  interlacing  freely  with  one  another;  and  finally,  much  reduced 
in  size,  are  lost  amongst  the  stronger  circular  fibres.  The  circular 


VESSELS  AND  NERVES  OF  THE  IRIS. 


367 


fibres  are  situate  more  at  the  back  of  the  iris,  and  produce,  by  their 
contraction,  the  many  transverse  folds  seen  on  that  surface.  They 
are  most  numerous  close  around  the  pupil  (sphincter  pupillcB),  and  are 
least  distinct  midway  between  this  and  the  ciliary  margin. 

Arteries  of  the  iris. — The  proper  vessels  for  the  supply  of  the  iris  are 
the  long  ciliary  and  anterior  ciliary  arteries. 


Fig.  379. 


a.  The  Img  ciliary  arteries, 
fig-  379,“  two  in  number,  and 
derived  from  the  ophthalmic, 
pierce  the  sclerotic  a little  be- 
fore, and  on  either  side  of,  the 
optic  nerve.  Having  gained 
the  interval  between  the  scle- 
rotic and  choroid  coats,  they 
extend  horizontally  forwards 
through  the  cellular  tissue 
(memh.  fusca)  to  the  annulus 
albidus.  In  this  -course  they 
nearly  correspond  in  direction 
to  the  axis  of  th.e  eyeball,  the 
outer  vessel  being,  however, 
a little  above,  and  the  inner 
one  a little  below  the  level  of 
that  line.  A.  short  space  be- 
hind the  fixed  margin  of  the 
iris,  each  vessel  divides  into  an 
upper  and  a lower  branch,  and 
these  anastomosing  with  the 
corresponding  vessels  of  the 
opposite  side  of  the  eye,  form 
a vascular  ring  (circw/MS  mq/or  iridis).  From  this  circle  smaller  branches  arise, 
which  converge  towards  the  pupil ; and  there,  freely  communicating  by  transverse 
offsets  from  one  to  another,  form  a second  circle  of  anastomosis  (circulus  mimrY 

b.  The  anterior  ciliary  arteries,  fig.  379,®  several  in  number,  but  smaller  than  the 
vessels  just  described,  are  supplied  from  the  muscular  and  lachrymal  branches  of 
the  ophthalmic  artery^  and  pierce  the  sclerotic  about  a line  behind  the  margin  of 
the  cornea;  finally,  they  divide  into  branches  which  join  the  circulus  major. 

c.  Besides  these  special  arteries,  numerous  minute  vessels  enter  the  iris  from 
the  ciliary  processes,  which  are  highly  vascular  in  their  structure. 


An  enlarged  view  of  the  arteriefe  of  the  iris.  (From  Ar- 
nold.)—a.  Optic  nerve,  b.  Sclerotic,  c.  Cili.iry  ligament. 
d.  Iris.  1.  Posterior  ciliary  arteries  perforating  the  scle- 
rotic. 2.  Long  (external)  ciliary  artery.  3.  Anterior 
(short)  ciliary  arteries.  (The  figure  is  larger  than  natural.) 


The  veins  of  the  iris  follow  closely  the  arrangement  of  the  arteries 
just  described.  The  canal  of  Fontana  appears  to  communicate  with 
this  system  of  vessels. 

The  nerves  for  the  supply  of  the  iris  are  named  ciliary : they  are 
numerous  and  large ; and  before  entering  the  iris,  divide  in  the  sub- 
stance of  the  annulus  albidus. 


The  ciliary  nerves,  fig.  354,  about  twenty  in  number,  and  derived  from  the 
lenticular-  ganglion  and  the  nasal  branch  of  the  ophthalmic  division  of  the  fifth 
nerve,  pierce  the  sclerotic  near  the  entrance  of  the  optic  nerve,  fig.  380,  c,  d,  and 
immediately  come  in  contact  with  the  choroid.  They  are  somewhat  flattened  in 
form,  are  partially  embedded  in  grooves  on  the  inner  surface  of  the  sclerotic,  and 
communicate  with  each  other  occasionally  before  entering  the  annulus  albidus. 
When  the  sclerotic  is  carefully  stripped  from  the  subjacent  structures,  these  nerves 
are  seen  lying  on  the  surface  of  the  choroid.  Within  the  substance  of  the  annulus 
albidus  the  ciliary  nerves  subdivide  minutely,  a few  being  lost  in  the  substance 
of  that  band,  but  the  greater  number  passing  on  to  the  iris.  On  account  of  its 
connexion  with  the  nerves,  Soemmerring  considered  the  annulus  albidus  a 


368 


THE  RETINA. 


[Figf.  380. 


ganglionic  structure,  naming  it 
cir cuius  gangliformis. 


Pupillary  membrane 
(membrana  pupillaris). — 
In  foetal  life  a delicate 
transparent  membrane  thus 
named  closes  the  pupil, and 
therefore  completely  sepa- 
rates the  anterior  from  the 
posterior  chamber  of  the 
aqueous  humour.  The  pu- 
pillary membrane  contains 
minute  vessels,  continuous 
with  those  of  the  iris  and 
of  the  capsule  of  the  crys- 
talline lens;  they  are  ar- 
ranged in  loops,  which  con- 
verge towards  each  other, 
but  do  not  quite  meet  at 
the  centre  of  the  pupil.  At 
about  the  seventh  or  eighth 
month  of  foetal  life  these 
vessels  gradually  disap- 
pear ; and,  in  proportion  as 
the  vascularity  diminishes,  the  membrane  itself  is  absorbed  from  near 
the  centre  towards  the  circumference.  At  the  period  of  birth,  often  a 
few  shreds,  sometimes  a larger  portion,  and  occasionally  the  whole 
membrane,  is  found  persistent. 


Choroid  and  iris,  exposed  by  turning  aside  the  sclero- 
tica.— c,  c.  Ciliary  nerves  branching  in  the  iris.  d.  Smaller 
ciliary  nerve,  e.  e.  Vasa  voriicosa.  h.  Ciliary  lig.nment 
and  muscle,  k.  Converging  fibres  of  the  greater  circle  of 
the  iris.  1.  Looped  and  knotted  form  of  these  near  the 
pupil,  with  the  converging  fibres  of  the  lesser  circle  of  the 
iris  within  them.  o.  'i'he  optic  nerve. — From  Zinn.] 


7.  THE  RETINA. 

The  retina  (tunica  nervea)  is  a delicate,  almost  pulpy  membrane, 
continuous  w'ith  the  optic  nerve,  and  thence  extending  within  the  cho- 
roid nearly  to  the  margin  of  the  crystalline  lens.  In  the  living  subject 
it  is  transparent;  but,  when  slightly  decomposed,  or  when  moistened 
with  alcohol  or  nitric  acid,  it  becomes  opaque,  and  assumes  a grayish- 
white  colour. 

The  retina  is  in  contact  by  its  outer  surface  with  the  choroid,  and 
by  its  inner  surface  with  the  hyaloid  membrane ; but,  as  far  forwards 
as  the  posterior  margin  of  the  ciliary  processes,  its  connexion  with 
these  two  structures  is  very  slight,  and  easily  torn  through.  At  the 
dentated  border  {ora  serrata)  of  the  ciliary  processes  the  retina  is 
somewhat  thickened,  and  seems  to  end  in  a defined  margin.  Modem 
observers,  how’ever,  (e.  g.  Valentin  and  Bidder,)  find  that  it  is  con- 
tinued over  the  inner  surface  of  the  ciliary  processes ; though,  from  its 
tenuity,  and  close  adherence  to  these  processes  and  to  the  hyaloid 
membrane,  it  is  with  difficulty  displayed.* 

The  concave  inner  surface  of  the  retina  presents  at  the  back  of  the 
eye  several  objects  of  interest.  Directly  in  a line  with  the  axis  of  the 


* This  is  seen  better  in  the  fetal,  than  in  the  adult  eye.  It  is  still  undecided  whether 
all,  or,  if  not,  which,  of  the  component  parts  of  the  retina  are  thus  prolonged. 


THE  RETINA— ITS  STRUCTURE. 


369 


eyeball  is  a circular  yellow  spot  {limbus  luteus),  about  a line  or  a line 
and  a half  in  diameter,  and  marked  in  the  centre  by  what  appears  like 
a minute  hole* — the  foramen  centrale  of  Soemmerring.  Nearly  two 
lines  to  the  inner  or  nasal  side  of  the  yellow  spot  is  a flattened  circular 
papilla  {colliculus),  corresponding  with  the  situation  in  which  the  optic 
nerve  pierces  the  choroid  coat.  Between  these  two  points  extends  a 
small  projection  or  fold  of  the  retina  {plica  centralis  retina;). 

Structure. — Three  very  different  structures  are  distinguishable  in  the 
retina ; an  outer  membrane  (the  membrane  of  Jacob),  an  inner  vascu- 
lar network,  and  an  intermediate  stratum  of  nervous  substance. 


a.  The  membrane  of  Jacobf 
may  be  raised  from  the  outer 
surface  of  theTetina  by  inject- 
ing air,  or  even  introducing 
mercury,  beneath  it  vrhen  the 
eye  is  under  water. 

By  microscopical  observa- 
tions, this  part  of  the  retina  has 
been  found  to  consist  of  small 
columns  or  rods  placed  at  right 
angles  with  the  surface  of  the 
membrane,  like  the  pile  of  vel- 
vet, fig.  381,,  A.  The  bodies 
referred  to  are  of  two  kinds, 
one  being  smaller  and  more 
numerous  than  the  other.  The 
small  rods  are  solid  and  six- 
sided  prisms,  narrowed  to  a 
point  at  tlie  end  next  the  cho- 
roid, d ; and  they  are  grouped 
round  the  larger  bodies.  These, 
which  are  named  by  Hannover 
“ twin  cones”  {coni  gemini), 
are  shorter  than  the  preceding, 
and  are  cleft  at  the  outer  end 
into  two  short  blunt  points. 

Viewed  on  the  outer  surface, 
fig.  381,  B,  this  structure  has 
the  appearance  of  a mosaic 
pavement.  The  ends  of  the 
little  cones  are  received  into 


Fig.  381. 


Fig.  A.  An  enlarged  plan  ofthe  retina,  in  section.  1.  The 
nervoas  structure,  viz.,  the  nerve-fibres  (6)  between  nerve- 
cells  (a,  c).  2.  Jacob’s  membrane.  3.  Inner  surface  of 
choroid,  d.  One  of  small  pointed  bodies  of  Jacob’s  mem- 
brane. 

Fig.  B.  The  outer  surface  of  Jacob’s  membrane.  (From 
Hannover’s  Recherckes  Microscopigues,  ^c.,  1844.) — Oppo- 
site e,  the  twin  cones  are  obscurely  seen,  not  being  in 
focus,  while,  at  the  lower  part  of  the  figure,  near  /,  the 
same  bodies  are  clearly  discernible.  Towards  the  right 
side  of  the  figure,  where  the  objects  are  disturbed,  the 
small  sheaths  on  the  pigment-  twin  cones  project  like  papillse,  atg,  the  small  rods  being 
cells  of  the  choroid ; each  poly-  f measure  lost  at  this  place.  And  the^se  (small 

1 • .11  j bodies)  are  seen  to  become  horizontal  towards  the  extre- 

gonal  pigment-cell  correspond-  gf  (J,g  object,  h,  where  some  are  in  disorder, 
mg  to  SIX  or  eight  of  the  twin 

cones,  with  the  more  numerous  simple  rods  which  surround  them,  fig.  381,  a. 

b.  Medullary  layer. — The  essential  element  of  the  retina,  and  that  on  which 
depends  its  capability  of  receiving  the  impressions  of  light,  is  an  expansion  of 
nervous  matter  derived  from  the  optic  nerve.  Diverging  from  the  opening  in  the 
choroid,  the  tubular  fibres  of  the  optic  nerve  radiate  towards  the  anterior  end  of 
the  retina,  the  fibres  becoming  more  slender,  and  the  spaces  between  them 
'increasing  in  width  as  they  advance  to  the  fore  part  of  the  eye ; and  they  are 
covered  on  the  inner  and  outer  surface  with  a layer  of  nerve-cells,  fig.  381,  a. 

As  regards  the  mode  of  termination  of  the  nerve-fibres,  anatomists  are  not 
agreed.  They  have  been  said  to  form  loops,  where  they  end  at  the  anterior 

* The  appearance  of  an  aperture  seems  to  be  produced  by  the  absence  at  this  point  of 
the  medullary  substance  of  the  retina,  the  vascular  layer  being  alone  continued  over  it, 
t So  named  after  Dr.  Jacob,  who  described  it  in  the  Phil.  Trans.,  1819. 


370 


THE  AQUEOUS  HUMOUR. 


margin  of  the  retina  (Valentin);  but  Hannover  states  that  his  observations  render 
it  probable  that  they  terminate  by  free  extremities.  While  the  manner  of  their 
termination  is  not  determined  with  certainty,  no  doubt  is  entertained  as  to  the 
place  at  which  it  occurs.  It  is  agreed,  at  least  as  regards  the  eye  of  the  lower 
animals,  that  none  of  the  fibres  end  at  the  bottom  of  the  eye,  all  reaching  the  fore 
part  of  the  organ,  as  before  mentioned. 

c.  The  vascular  layer  (lamina  vasculosa  fetinse)  consists  of  a fine  network  of 
arteries  and  veins,  held  together  by  cellular  membrane.  It  supports  the  nervous 
substance  of  the  retina,  which  may  readily  be  washed  from  its  outer  surface  after 
short  maceration  in  water.  The  arteries  entering  into  the  formation  of  this  layer 
are  principally  derived  from  the  arteria  centralis  retinee,  a branch  of  the  ophthalmic, 
which,  conducted  through  the  substance  of  the  optic  nerve,  enters  the  retina  at 
the  centre  of  the  optic  papilla  and  immediately  gives  off  several  diverging  branches. 
The  posterior  ciliary  arteries  likewise  send  minute  twigs  to  assist  in  forming  the 
vascular  layer  of  the  retina.  The  vems  are  considerably  larger  and  more  tortuous 
than  the  arteries,  but  follow  much  the  same  course  and  distribution. 


Fig.  382. 


8.  THEAQUEOUSHUMOUR. 

The  aqueous  humour  (humor  aqueus)  is 
a colourless,  transparent,  watery  fluid, 
containing  a minute  quantity  of  albumen 
and  chloride  of  sodium  in  solution,  which 
occupies  the  interval  between  the  cornea 
in  front,  and  the  crystalline  lens  and 
folded  ends  of  the  ciliary  processes  be- 
hind. The  space  thus  bounded  is  partially 
divided  by  the  iris  into  two  compartments 
of  unequal  size  {anterior  and  posterior 
chambers),  of  which  that  in  front  of  the 
iris  (the  anterior  chamber)  is  the  larger. 
In  the  foetus,  the  separation  between  the 
two  is  completed  by  the  membrana  pupil- 
laris. 

The  membrane  of  the  aqueous  humour. — It  has 
been  supposed  that  the  aqueous  humour  is 
secreted  from  the  surface  of  a serous  membrane, 
known  under  this  name,  lining  the  walls  of  this 
cavity.  A thin  membrane  has  already  been 
described  as  covering  the  back  of  the  cornea, 
and  thence  prolonged,  over  the  edge  of  die 
ciliary  ligament,  to  the  outer  margin  of  the  iris, 
Plan  of  the  structures  in  the  fore  beyond  which  it  has  not  been  traced.  Another 
part  of  the  ey^,  seen  in  section.— 1.  membrane  exists  over  the  posterior  surface 

4.cCo'<r'5.LMhisaf^  of  the  iris  and  the  projecting  ends  of  the  ciliary 

this  is  seen  the  canal  of  Fontana.  6 processes;  but,  as  yet,  no  corresponding  struc- 
Ciliary  processes.  7.  Iris.  8.  Retina,  ture  has  been  demonstrated  either  over  the 
9.  Hyaloid  membrane'.  10.  Canal  of  capsule  of  the  Crystalline  lens,  or  over  the  fore 
Petit  (made  too  large).  11.  Membrane  r ■ 

of  the  aqueous  humour  (too  thick),  a.  P 
Aqueous  hiirnour:  anterior  chamber 

and  (a)  posterior  chamber.  6.  Crystal-  9.  THE  VITREOUS  HUMOUR, 

line  lens.  c.  Vitreous  humour. 

The  vitreous  humour  occupies  about 
the  posterior  two  thirds  of  the  cavity  of  the  eye,  and  consists  of  a 
clear,  thin  fluid  {humor  vitreus),  inclosed  in  a fine,  transparent  mem- 
brane {membrana  hyaloidea).  This  membrane  not  only  forms  a 
general  investment  for  the  whole  bulk  of  fluid,  but  sends  numerous 


THE, VITREOUS  HUMOUR. 


371 


delicate  cellular  processes  inwards  to  inclose  and  support  the  humour 
in  the  form  of  a semi-solid  gelatinous  body,  called  the  vitreous  body. 
The  vitreous  body  (corpus  vitreum)  is  irregularly  spheroidal  in  form, 
and  presents  at  its  fore  part  a cup-shaped  depression,  which  lodges 
the  posterior  or  larger  segment  of  the  crystalline  lens.  On  the  surface 
of  the  corpus  vitreum,  immediately  around  this  depression,  are  a 
number  of  closely  set  black  lines,  so  arranged  as  to  form  a circle  of 
rays  round  the  margin  of  the  lens.  When  first  exposed,  by  separating 
the  vitreous  body  from  the  ciliary  processes,  these  lines  appear  of 
unequal  thickness,  from  the  presence  of  a quaiitity  of  adhering  pig- 
ment; but,  when  the  colouring  matter  is  removed  by  careful  washing, 
regular  projections  or  folds  of  membrane  are  brought  into  view  {pro- 
cessus ciliares  hyaloidece),  the  aggregate  of  which  is  called  the  zone  of 
Zinn,  or  zonula  ciliaris.  Their  inner  ends  do  not  quite  touch  the  lens, 
a narrow  interval  {zonula  lucida)  being  left  where  the  hyaloid  mem- 
brane assists  in  bounding  the  posterior  chamber  of  the  eye.  In  their 
mode  of  arrangement,  these  folds  resemble  the  ciliary  processes,  in  the 
intervals  of  which  they  are  received,  and  to  which  they  are  attached 
by  cellular  tissue.  They  differ  from  the  ciliary  processes,  however,  in 
being  rather  longer  and  much  less  prominent. 

The  hyaloid  membrane,  for  about  a line  outside  the  depression  for 
the  crystalline  lens,  consists  of  two  layers,  fig.  382,“.  One  of  these, 
immediately  inclosing  the  vitreous  humour,  passes  behind  the  posterior 
division  of  the  capsule  of  the  lens;  whilst  the  other,  adhering  to  the 
ciliary  processes,  appears  to  end  in  the  anterior  part  of  the  capsule 
close  to  the  margin.  The  space  left  between  the  two  layers  of  mem- 
brane forms  round  the  circumference  of  the  lens  a circular  passage, 
the  canal  of  Petit  {canal  godronne),^°  the  interior  of  which  is  crossed 
at  regular  intervals  by  imperfect  membranous  septa.  When  the  space 
is  filled  with  air  injected  through  the  outer  membrane,  an  appearance 
as  of  a string  of  beads  is  produced ; the  situation  of  the  bands  above 
mentioned  is  then  marked  by  a series  of  constrictions,  between  w'hich 
the  walls  of  the  canal  are  forced  to  project. 

Behind  the  ora  serrata  of  the  corpus  eiliare,  the  outer  surface  of  the 
hyaloid  membrane  is  in  contact,  but  is  very  slightly  connected,  with 
the  concave  surface  of  the  retina ; but,  in  front  of  the  serrated  line, 
it  has  been  seen  that  the  two  structures  are  inseparably  united.  Oppo- 
site the  optic  papilla  is  a small  aperture  in  the  vitreous  body;  through 
which,  in  the  fcetal  eye,  a minute  branch  of  the  central  artery  of  the 
retina  enters.  The  vessel  extends  through  the  middle  of  the  vitreous 
humour  to  the  back  of  the  crystalline  lens;  and  in  this  course  it  is 
lodged  in  a tubular  process  of  the  hyaloid  membrane,  called  the  hyaloid 
canal. 

No  vessels  or  nerves  have  been  traced  in  the  membrane  of  the 
vitreous  humour. 

Hannover*  has  lately  investigated  the  arrangement  of  the  vitreous  body  and  its 
membrane.  After  long  maceration  in  chromic  acid,  he  finds  it  crossed  by  about 
180  delicate  membranous  septa,  disposed  somewhat  like  the  segments  of  the  pulp 
of  an  orange,  with  the  angles  of  the  inclosed  spaces  directed  towards  the  axis  of 

* Muller’s  Archiv,  1845. 

I 


372 


THE  CRYSTALLINE  LENS. 


the  eyeball.  The  sectors  do  not  however  meet  at  this  line,  but  leave  a cylindrical 
portion  of  the  vitreous  body,  of  a homogeneous  te.xture,  extended  between  the 
of)tic  nerve  and  the  centre  of  the  posterior  surface  of  the  lens.  This  is  larger  in 
the  foetal  than  in  the  adult  eye  j and  through  it  passes  the  central  artery.  The 
fluid  inclosed  in  the  areolae  of  the  vitreous  body  becomes  slightly  gelatmous  after 
tills  maceration. 


10. 


THE  CRYSTALLINE  LENS. 


The  crystalline  lens,  fig.  382,  b,  is  a colourless,  transparent,  solid 
body,  having  the  form  of  a doubly  convex  lens,  situate  directly  in  the 
axis  of  vision,  and  interposed  between  the  aqueous  and  vitreous 
humours.  Its  anterior  surface  projects  within  a very  short  distance  of 
the  back  of  the  iris,  and  assists  in  bounding  the  posterior  chamber  of 
the  eye.  The  posterior  surface,  more  convex  than  the  anterior,  is 
received  into  a depression  on  the  fore  part  of  the  vitreous  body.  The 
circumference  is  circular,  rounded  at  the  margin,  and  corresponds 
with  the  circular  canal  (canal  of  Petit)  already  described  in  the  hya- 
loid membrane. 

The  crystalline  lens  is  inclosed  in  a transparent  capsule,  the  cha- 
racter of  which  diflers  much  on  its  fore  and  back  part.  That  portion 
of  the  capsule  which  covers  the  anterior  surface  of  the  lens  is  thick, 
and  of  a peculiar,  firm,  semi-cartilaginous  structure,  retaining  its 
transparency^  and  brilliancy  (like  the  layer  already  described  at  the 
back  of  the  cornea)  when  macerated  in  water,  or  even  after  being 
immersed  in  alcohol  or  dilute  nitric  acid.  The  posterior  division  of 
the  capsule,  on  the  contrary,  is  thin  and  membranous,  adheres  closely 
to  the  hyaloid  membrane,  and  is  whitened  by  the  action  of  spirit. 
The  circumference  of  the  capsule  is  connected  with  the  inner  folded 
ends  of  the  ciliary  processes. 

The  proper  substance  of  the  lens  adheres  but  slightly  to  the  inner 

surface  of  the  capsule;  a small  quantity 
of  fluid  occasionally  intervening,  which 
is  called  the  liquor  Morgagni.  In  a fresh 
lens  the  outer  portion  is  soft  and  gelati- 
nous. Beneath  this  is  a firmer  layer; 
and  in  the  centre  is  the  hardest  part  or 
nucleus.  After  immersion  in  alcohol, 
nitric  acid,  or  boiling  water,  these  seve- 
ral parts  assume  a uniform  density,  and 
are  then  seen  to  be  made  up  of  essen- 
tially the  same  structures.  When  so 
treated,  the  lens  may  be  separated  into 
Lens,  hardened  in  spirit  and  par-  concentric  lamellae,  all  of  which  split  in 
pK as  welUsmtoTam^^^^^^  the  Same  way  into  segments,  the  apices 

nified  3i  diameters.— After  Arnold.]  meeting  at  tvvm  Opposite  points  in  the 

circumference,  fig.  383,^.  These  layers 
are  further  composed  of  microscopic  fibres  arranged  side  by  side,  and 
adhering  together  by  regularly  dentated  margins.  The  crystalline 
lens  of  the  adult  seems  to  be  devoid  of  blood-vessels;  but  in  the  fcctus 
numerous  vessels  exist  in  the  capsule,  which  readily  admit  of  injection. 

The  capsular  artery  in  the  foetus  leaves  the  arteria  centralis  retinae 


[Fig.  383. 


THE  EAR. 


373 


at  the  centre  of  the  optic  papilla,  and  crossing  through  the  substance 
of  the  corpus  vilreum,  as  already  described,  enters  the  posterior  por- 
tion of  the  capsule  of  the  lens,  where  it  divides  into  radiating  branches. 
These  form  a fine  network,  turn  round  the  margin  of  the  lens,  and 
extend  forward  to  become  continuous  with  the  vessels  in  the  pupillary 
membrane  and  the  iris.  The  vessels  are  contained  in  the  capsulo- 
pupillary  membrane,  which  connects  in  the  foetus  the  pupillary  edge 
of  the  iris  with  the  margin  of  the  capsule  of  the  lens.*-  This  vessel  is 
found  only  in  the  foetal  eye. 

Changes  in  the  lens  by  age. — In  form,  colour,  degree  of  transparency,  and  density, 
the  lens  presents  marked  differences  at  different  periods  of  life. 

In  the  fatus,  the  lens  is  nearly  spherical : it  has  a slightly  reddish  colour,  not 
perfectly  transparent,  and  is  softer  and  more  readily  broken  down  than  at  a more 
advanced  age. 

In  the  adult,  the  anterior  surface  of  the  lens  becomes  less  convex  than  the  pos- 
terior ; and  the  substance  of  the  lens  is  firmer,  colourless,  and  transparent. 

In  old  age,  it  is  flattened  on  both  surfaces;  it  assumes  a yellowish  or  amber 
tinge,  and  is  apt  to  lose  its  transparency  as  it  gradually  increases  in  toughness 
and  specific  gravity. 


THE  EAR. 

The  organ  of  hearing  is  divisible  into  three  parts : the  external  ear, 
the  tympanum  or  middle  ear,  and  the  labyrinth  or  internal  ear;  and 
of  these  the  first  two  are  to  be  considered  as  accessories  or  appen- 
dages to  the  third,  which  is  the  sentient  portion  of  the  organ. 

A.  THE  EXTERNAL  EAR. 

Included  in  this  term  are  the  pinna, — the  part  of  the  outer  ear 
which  projects  from  the  side  of  the  head, — and  the  meatus  or  passage 
which  leads  thence  to  the  tympanum,  and  is  closed  at  its  inner  ex- 
tremity by  the  membrane  interposed  between  it  and  the  middle  ear 
(membrana  tympani). 

1.  THE  PINNA. 

The  pinna,  or  auricle,  fig.  384,^ituate  behind  the  articulation  of  the 
lower  jaw,  and  in  front  of  the  mastoid  process  of  the  temporal  bone, 
is  flattened  and  ovoid,  folded  at  the  margins,  and  irregularly  concave 
towards  the  opening  of  the  meatus  auditorius,  round  which  it  is  at- 
tached. The  fixed  portion  of  the  pinna  is  in  front  of,  and  a little 
below  its  centre ; and  the  free  and  expanded  part  extends  from  this 
point  backwards  and  outwards,  forming  an  angle  with  the  opposed 
surface  of  the  cranium. 

Though  the  general  form  of  the  auricle  is  concave,  (to  fit  it  for 
collecting  and  concentrating  the  undulations  of  sound,)  the  outer  sur- 
face is  marked  by  several  winding  ridges  and  hollows,  to  which  dis- 
tinct names  have  been  given.  The  largest  and  deepest  concavity,  a 

* Some  authors  (Albinus,  Zinn,  &c.)  state  that  they  have  traced  vessels  from  the  capsule 
entering  the  substance  of  the  lens  itself. 

VOL.  II.  32 


374 


THE  PINNA. 


Fig.  384. 


little  below  the  centre  of  the  organ,  is 
called  the  concha,  fig.  384,®;  it  surrounds 
the  entrance  to  the  external  auditory 
meatus,  and  is  unequally  divided  at  its 
upper  part  by  a ridge,  which  is  the  be- 
ginning of  the  helix.  In  front  of  the 
concha,  and  projecting  backwards  over 
the  meatus  auditorius,  is  a conical  promi- 
nence, the  trugws,*frequently  covered  with 
hairs.  Behind  this,  and  separated  from 
it  by  a deep  notch  (incisura  intertragicu), 
is  another  smaller  elevation,  the  anli- 
ti'agus,*  which  is  directed  upwards  and 
forwards,  and  also  assists  in  bounding 
the  concha.  Beneath  the  antitragus,  and 
forming  the  lower  end  of  the  auricle,  is 
a thick  rounded  piece  called  the  lobvh,^ 
. . ^ , r , which  is  devoid  of  the  firmness  and  elas- 

A view  of  the  left  ear  in  its  natural  ...  , . , ^ , 

state.  1,  2.  The  origin  and  termination  ticity  that  characterize  the  rest  01  the 
the;  helix.  3.  The  antihelix.  4.  pinna.  The  thinner  and  larger  portion 

The  lobus  of  the  external  ear.  7.  ot  the  pinna  IS  bounded  by  a prominent 
Points  to  the  scapha,  and  is  on  the  front  and  iiicurved  margin,  licUx,'' which, 
and  top  of  the  pinna.  8.  The  concha.  . . . ^ • i • i 

9.  The  meatus  auditorius  externus.  springing  above  and  rather  within  the 

tragus,  from  the  hollow  of  the  concha, 
surrounds  the  upper  and  posterior  margin  of  the  auricle,  and  gra- 
dually loses  itself  in  the  back  part  of  the  lobule.  Within  the  helix 
is  another  curved  ridge,  the  antihelix,^  which  may  be  said  to  begin 
below,  at  the  antitragus.  From  this  point  it  sweeps  round  the  hollow 
of  the  concha,  (forming  the  posterior  boundary  of  that  concavity,) 
and  divides  ultimately  into  two  secondary  ridges,  which  diverge  as 
they  ascend  to  the  helix. 

Fosscb  of  the  pinna. — Between  the  helix  and  the  single  portion  of  the 
antihelix  is  a narrow  curved  groove,  the  fossa  of  the  helix  (fossa  in- 
nominata,  scaphoidea) ; and  betwmen  the  bifurcations  of  the  upper 
part  of  the  antihelix  is  a somewhat  triangular  depression,  the  fossa  of 
the  antihelix  (fossa  triangularis  vel  ovalis)^. — The  largest  of  the  fossae, 
the  concha,  has  been  already  described. 

The  inner  or  posterior  surface  of  the  pinna  looks  towards  the  side 
of  the  head,  and  presents  several  irregularities,  the  reverse  of  those 
just  mentioned  as  on  the  outer  side.  The  largest  prominences  corre- 
spond to  the  concha  and  fossa  of  the  helix ; and  the  principal  depres- 
sion is  in  the  situation  of  the  antihelix. 

Structure  of  the  pinna. — The  pinna  is  composed  of  a thin  plate  of 
cartilage  covered  with  skin;  but  at  certain  parts  the  cartilage  is  defi- 
cient, and  its  place  is  supplied  by  fibrous  membrane,  cellular  tissue, 
and  fat.  The  pinna  has  also  several  ligaments  and  small  muscles, 
which  assist  in  preserving  its  position  and  form. 

a.  The  shin  of  the  pinna  is  thin,  closely  adherent  to  the  cartilage, 
and  supplied  with  sebaceous  follicles,  which  are  most  abundant  in  the 
hollow  of  the  concha. 


MUSCLES  OF  THE  PINNA. 


375 


b.  The  cartilage  presents  all  the  inequalities  of  surface  already  de- 
scribed as  apparent  in  the  upper  part  of  the  pinna  ; and  on  this  structure, 
in  fact,  the  irregularities  are  formed.  But  the  cartilage  does  not  ex- 
tend into  the  lobule,  which  is  made  up  of  fat  and  tough  cellular  mem- 
brane attached  to  the  edge  of  the  cartilage  and  inclosed  in  a fold  of 
the  skin.  Between  the  tragus  and  beginning  of  the  helix  the  cartilage 
is  again  deficient,  the  deep  notch  there  left  being  bridged  over  in  the 
natural  state  by  dense  fibrous  membrane.  Behind  the  antitragus,  and 
between  it  and  the  end  of  the  helix,  is  a srnaller  notch,  which  gives  to 
the  posterior  margin  of  the  auricle  a tail-like  end,  directed  towards 
the  lobule.  At  the  fore  part  of  the  pinna,  opposite  the  first  bend  of 
the  helix,  is  a small  conical  projection  of  the  cartilage,  called  the  pro- 
cess of  the  helix,  to  which  the  anterior  ligament  is  attached.  Behind 
this  process  is  a short  vertical  slit  in  the  helix  ; and  on  the  surface  of 
the  tragus  is  a similar  but  somewhat  longer  fissure.  The  substance 
of  the  cartilage  is  naturally  brittle,  but  is  much  strengthened  by  a firm 
fibrous  perichondrium. 

c.  Of  the  ligaments  of  the  pinna,  the  most  important  are  two  which 
assist  in  attaching  it  to  the  side  of  the  head.  The  anterior  ligament, 
broad  and  strong,  extends  from  the  process  of  the  helix  to  the  root  of 
the  zygoma.  The  posterior  ligament  fixes  the  back  of  the  auricle  (op- 
posite the  concha)  to  the  outer  surface  of  the  mastoid  process  of  the 
temporal  bone.  A few  fibres  attach  the  tragus  also  to  the  root  of  the 
zygoma. 

The  proper  ligaments  of  the  pinna  are  so  placed  as  to  cross  over  the 
fissures  and  intervals  left  in  the  cartilage  ; thus,  a strong  band  of  fibrous 
tissue  stretches  from  the  tragus  to  the  beginning  of  the  helix,  crossing 
over  the  meatus,  and  completing  the  boundaries  of  the  concha.  An- 
other layer  of  fibres  exists  on  the  inner  or  cranial  surface  of  the  pinna, 
which  assists  in  maintaining  the  regular  arched  form  of  the  auricle. 

d.  Of  the  muscles  of  the  pinna,  those  are  attached  by  one  end  to 

the  side  of  the  head  and  move  the  pinna  as  a whole,  have  been  already 
described  (vol.  i.  p.  334) ; there  remain  to, be  examined  several  smaller 
muscles,  composed  of  thin  layers  of  pale  fibres,  which  extend  from 
one  part  of  the  pinna  to  another.  These  are  the  proper  muscles  of  the 
organ;  and,  if  sufficiently  strong,  would  act  in  modifying  the  form  of 
that  part  of  the  external  ear.  Five  small  muscles  are  generally  enu- 
merated in  each  ear,  though  some  writers  have  increased  this  number. 

1.  The  smaller  muscle  of  the  helix  (m.  minor  helicis)  fig.  385/,''  is  a small  bundle 
of  oblique  fibres,  lying  over,  and  firmly  attached  to  that  portion  of  the  helix  which 
springs  from  the  bottom  of  the  concha. 

2.  The  greater  muscle  of  the  helix  (m.  major  helicis),',®  lies  vertically  along  the 
anterior  margin  of  the  pinna.  By  its  lower  end  it  is  attached  to  the  process  of 
the  helix ; and  above,  its  fibres  terminate  opposite  the  point  at  which  the  ridge 
of  the  helix  turns  backwards. 

3.  The  muscle  of  the  tragus  (m.  tragicus),®,®  is  a flat  bundle  of  short  fibres  cover- 
ing the  outer  surface  of  the  tragus : its  direction  is  nearly  vertical. 

4.  The  muscle  of  the  antitragis  (m.  antitragicus),^,®  is  placed  obliquely  over  the 
antitra^s  and  behind  the  lower  part  of  the  antihelix.  It  is  fixed  at  one  end  of 
the  antitragus,  from  which  point  its  fibres  converge  slightly  to  be  inserted  into  the 
tail-like  extremity  of  the  helix,  above  and  behind  the  lobule. 

5.  The  transverse  muscle  (m.  transversus  auriculae),  fig.  386,®  lies  on  the  inner  or 


376 


EXTERNAL  AUDITORY  CANAL. 


cranial  surface  of  the  pinna,  and  consists  of  radiating  fibres  which  extend  fropi 
the  back  of  the  concha  to  the  prominence  which  corresponds  with  the  groove  of 
the  helix.  The  name  obliqims  amis  (Tod),“  has  been  applied  to  a few  fibres  stretch- 
ing from  the  back  of  the  concha  to  the  convexity  directly  above  it  3 but  these 
appear  rather  to  forni  a part  of  the  transverse  muscle. 


[Fig.  385.  Fig.  386. 


Fig.  385  represents  the  cartilage  of  the  external  ear,  with  some  of  its  muscles.  1,  2.  The  he- 
licis  major  muscle  on  the  front  of  the  helix.  3,  4.  The  helicis  minor  muscle.  5,  6.  The  tragiciis 
muscle  on  the  front  surface  of  the  tragus.  7,  8.  The  antitragicus  muscle. — S.  & H.] 

Fig.  386  represents  a view  of  the  muscles  on  the  inner  surface  of  the  pinna. — 5.  The  transverse 
muscle  of  the  auricle.  6.  The  oblique  muscle. 

The  pinna  is  supplied  with  vessels  and  nerves  from  several  different 
sources,  and  these  (particularly  the  vessels)  communicate  freely  on  its 
surface. 

e.  Arteries  of  the  Pinna. — The  posterior  auricular  artery,  a branch  from  the  exter- 
nal carotid,  is  distributed  chiefly  on  the  posterior  or  inner  surface,  but  sends  small 
branches  round  and  through  the  cartilage  to  ramify  on  the  outer  surface  of  the 
pinna.  Besides  this  artery,  the  auricle  receives  others  {anterior  auricular)  from  the 
temporal  in  front,  and  a small  artery  from  the  occipital  behind. 

/.  The  veins  correspond  much  in  their  course  with  that  of  the  arteries.  They 
join  the  temporal  vein,  and  return  their  blood  therefore  through  the  external 
jugular. 

g.  Nerves  of  the  Pinna. — The  great  auricular  nerve,  a branch  from  the  cervicJ 
plexus,  supplies  the  greater  part  of  the  back  of  the  auricle,  and  sends  small  fila- 
ments with  the  posterior  auricular  artery  to  the  outer  surface  of  the  lobule  and  part 
of  the  ear  above  it.  The  posterior  auricular  nerve,  derived  from  the  facial,  after 
communicating  with  the  auricular  branch  of  the  pneumo gastric,  ramifies  on  the 
back  of  the  ear  and  supplies  the  retrahent  muscle.  The -upper  muscles  of  the 
auricle  receive  their  supply  from  the  temporal  branches  of  the  same  nerve.  The  auri- 
culo-temporal  nerve,  a branch  of  the  third  division  of  the  fifth  nerve,  gives  fila- 
ments chiefly  to  the  outer  and  anterior  surface  of  the  pinna. 

2.  THE  EXTERNAL  AUDITORY  CANAL. 

The  external  auditory  canal  (meatus  auditorius  externus),  fig.  387, 
extends  from  the  bottom  of  the  concha  to  the  membrane  of  the  tym- 
panum, and  serves  to  convey  to  the  middle  chamber  of  the  ear  the 
vibration  of  sound  collected  by  the  auricle.  The  canal  is  rather  more 


THE  MIDDLE  EAR  OR  TYMPANUM. 


377 


than  an  inch  in  length,  and  its' course  Fiff.  387. 

inwards  is  slightly  tortuous.  Beginning 
at  the  concha,  it  inclines  at  first  up- 
wards and  forwards,  then  makes  a 
little  turn  backwards,  and  finally  dips 
downwards  and  forwards  to  its  termi- 
nation. The  caliber  of  the  passage  is 
smallest  about  the  middle ; the  outer 
opening  is  larger  in  the  vertical  diame- 
ter, but  the  tympanic  end  of  the  tube 
is  slightly  oval  in  the  opposite  direc- 
tion. Owing  chiefly  to  the  oblique  di- 
rection of  the  membrana  tympani,  the 
floor  of  the  meatus  is  longer  than  its 

r Horizontal  section  of  the  external  meatus 

_ seen  from  above.  (After Soemmerring.) — 1. 

The  meatus  is  composed  of  a partly  skin  of  the  face  in  front  of  the  ear.  2,  Skin 

rartilao-inmn?  nartlvosspoiistlibo  lined  of  the  head  behind  the  ear.  3.  Mastoid  pro- 
CdrUiaginOUS,  pariiy  osseous  LUDe,linea  4.  Osseous  part  of  the  external  audi- 

by  a prolongation  of  the  skin  of  the  tory  meatus.  6.  Hinder  part  of  the  pinna, 

• cut  through.  6.  Lobule.  7.  Cartilage  of 

pinild.  auricle  seen  in  section.  8.  External  audi- 

-7  • r ^ tory  meatus.  9.  Membrana  tympani.  10. 

а.  The  cartilaginous  part  oi  the  meatus  Dura  mater, 
forms  somewhat  less  than  half  the  length 

of  the  passage.  It  is  continued  from  the  cartilage  of  the  pinna,  and  is  firmly  at- 
tached to  the  rough  and  prominent  margin  of  the  external  auditory  aperture  in 
the  temporal  bone.  The  substance  of  the  cartilaginous  tube  is  continuous  with 
that  of  the  auricle  only  by  a narrow  slip  ] the  two  parts  of  the  cartilage  being 
nearly  separated  by  two  or  three  deep  fissures  {fissures  of  Santorini),  which  are 
directed  across  the  axis  of  the  canal.  There  is  a large  deficiency  of  the  cartilage 
also  at  the  upper  part  of  the  meatus,  the  space  being  filled  up  by  dense  fibrous 
membrane. 

б.  The  osseous  portion  of  the  meatus,  which  is  a little  longer  and  rather  narrower 
than  the  cartilaginous  part,  extends  through  the  substance  of  the  temporal  bone, 
from  the  external  auditory  foramen  to  the  membrane  which  forms  the  outer  wall 
of  the  tympanum  (membrana  tympani).  At  the  inner  end  of  the  canal  is  a 
shallow  groove,  which  extends  round  the  sides  and  door  of  the  meatus,  but  is 
deficient  above ; into  this  the  margin  of  the  membrane  referred  to  is  inserted. 

c.  The  skin  of  the  meatus  is  continuous  with  that  covering  the  pinna,  but  is 
very  thin,  and  becomes  gradually  thinner  towards  the  bottom  of  the  passage.  It 
is  firmly  adherent  to  the  sides  of  both  the  cartilaginous  and  the  osseous  parts  of 
the  canal;  and,  at  the  bottom  of  this,  the  epidermis  is  stretched  over  the  surface 
of  the  membrana  tympani,  forming  the  outer  layer  of  that  structure.  After  mace- 
ration in  water,  or  when  decomposition  is  advanced,  the  cutaneous  lining  of  the 
passage  may- be  separated  and  drawn  out  entire,  and  then  it  appears  as  a small 
tube  closed  at  one  end  somewhat  like  the  finger  of  a glove.  The  skin  is  covered 
with  fine  hairs,  and  contains  many  little  oval  bodies  of  a brownish-yellow  colour, 
which  are  glands  for  secreting  the  cerumen  or  ear-wax  {glandulce  cemminosce) . 
These  glands  are  most  abundant  about  the  middle  of  the  canal,  where  their  nu- 
merous openings  may  be  seen  to  perforate  the  skin. 

d.  Vessels  and  nerv&s. — The  external  auditory  meatus  is  supplied 
with  arteries  from  the  posterior  auricular,  internal  maxillary,  and 
temporal  arteries;  and  with  nerves  chiefly  from  the  temporo-auricular 
branch  of  the  fifth  nerve. 


B.  THE  MIDDLE  EAR  OR  TYMPANUM. 

The  tympanum,  or  drum,  the  middle  chamber  of  the  ear,  is  a nar- 

32* 


378 


CAVITY  OF  THE  TYMPANUM. 


row,  irregular  cavity  in  the  substance  of  the  temporal  bone,  placed 
between  the  inner  end  of  the  external  auditory  canal  and  the  labyrinth. 
It  receives  the  atmospheric  air  from  the  pharynx  through  the  Eusta- 
chian tube,  and  contains  a chain  of  small  bones,  by  means  of  which 
the  vibrations,  communicated  at  the  bottom  of  the  external  meatus  to 
the  membrana  tympani,are  conveyed  across  the  cavity  to  the  internal 
ear, — the  sentient  part  of  the  organ.  The  tympanum  contains  like- 
wise minute  muscles  and  ligaments  which  belong  to  the  bones  referred 
to,  as  well  as  some  nerves  which  end  within  this  cavity,  or  Only  pass 
through  it  to  other  parts.  The  cavity  opens,  or  is  continued,  into  cells 
(mastoid)  of  the  temporal  bone,  and  through  it  the  atmospheric  air 
reaches  those  cells. — The  boundaries,  foramina,  and  canals  of  the 
tympanum  will  be  first  described,  and  then  the  parts  contained  in  the 
cavity  will  come  under  examination. 


1.  THE  CAVITY  OF  THE  TYMPANUM. 

This  space  is  very  narrow  from  without  inwards,  but  measures 
from  before  backwards  and  from  above  downwards  nearly  half  an 
inch.  For  the  sake  of  greater  precision  in  describing  the  several  parts 
seen  on  the  surfaces  of  bone  which  bound  the  tympanum,  it  is  usual  to 
consider  the  cavity  as  presenting  a roof  and  a floor,  an  outer  and  an 
inner  wall,  an  anterior  and  a posterior  boundary. 

The  roof  of  the  tympanum  is  formed  by  a thin  plate  of  bone,  which 
may  be  easily  broken  through,  so  as  to  obtain  a view  of  the  tympanic 
cavity  from  above;  and  is  situate  in  the  upper  part  of  the  petrous  por- 
tion of  the  temporal  bone  near  the  angle  of  union  with  the  squamous 
portion.  The  floor  is  very  narrow,  the  outer  and  inner  boundaries 
meeting  at  an  acute  angle. 

The  outer  wall  is  formed  by  a thin  semi-transparent  membrane 
(membrana  tympani),  which  closes  the  inner  end  of  the  external  audi- 
tory meatus,  and,  to  a small  extent,  by  bone. 

The  membrana  tympani,  fig.  388,  a,  b,  is  nearly  circular,  and  is 

slightly  concave  on  the  outer  sur- 
Fig.  388.  face.  It  is  inserted  into  the  groove 

already  noticed  at  the  end  of  the 
meatus  externus,  and  so  obliquely 
that  the  membrane  inclines  towards 
the  anterior  and  lower  part  of  the 
canal  at  an  angle  of  about  45°. 
The  handle  of  one  of  the  small 
bones  of  the  tympanum,  the  mal- 

Membrana  tympani  from  the  outer  (A)  and  leuS,  descends  between  the  middle 
pan™. ‘2'  mXu^  t®st7pes.^r^™cL‘^™'  inner  layers  of  the  membrana 

tympani  to  a little  below  its  cen- 
tre, and  is  firmly  fixed  to  it ; and,  as  the  direction  of  the  process  of  the 
bone  is  slightly  inwards,  the  outer  surface  of  the  membrane  is  thereby 
rendered  concave. 

Structure  of  the  Membrane. — Though  very  thin^  the  membrana  tympani  is  co>n- 
posed  of  three  distinct  structures ; a prolongation  of  the  cuticle  of  the  externa) 
meatus  forms  the  outer  layer ; the  mucous  membrane  lining  the  cavity  of  the 


INNER  WALL  OF  THE  TYMPANUM. 


379 


tympanum  furnishes  an  inner  layer  j and  between  those  two  is  the  proper  sub- 
stance of  the  membrane,  made  up  of  fine,  closely  arranged  fibres.  The  greater 
number  of  the  fibres  radiate  from  near  the  centre  to  the  circumference  ; but  within 
these  are  circular  fibres,  which  are  more  scattered  and  indistinct,  except  close  to 
the  margin  of  the  membrane,  where  they  form  a dense,  almost  ligamentous  ring. 
Concerning  the  precise  nature  of  the  fibres  of  the  membrana  tympani,  anatomists 
are  not  agreed.* 

Immediately  in  front  of  the  ring  of  bone  into  which  the  membrana 
tympani  is  inserted,  a small  fissure  {fissura  Glasseri)  opens  into  the 
glenoid  cavity  of  the  temporal  bone.  It  lodges  a little  muscle  or  liga- 
ment, which  is  inserted  into  the  long  process  of  the  malleus.  To  the 
inner  side  of  this  fissure  is  the  opening  of  a small  canal,f  through 
which  the  chorda  tympani  nerve  escapes  from  the  cavjly  of  the  tympa- 
num and  the  skull. 


Fig-.  389. 


A view  of  the  inner  wall  of  the  tympanum,  from  Gordon  (Engravings  of  the  Skeleton,  1818). — 
1.  Openings  of  mastoid  cells.  2.  Fenestra  ovalis.  3 Fenestra  rotunda.  4.  Promontory.  5. 
Aqueduct  of  Fallopius.  6.  Junction  of  the  canal  for  the  chorda  tympani  w'iih  the  aqueduct.  7. 
Processus  cochleariformis.  8.  Canal  of  the  tensor  tympani.  9.  Eustachian  tube.  10.  Orifice 
of  the  carotid  canal. 

The  inner  wall  of  the  tympanum,  fig.  389,  which  is  formed  by  the 
outer  surface  of  the  internal  ear,  is  very  uneven,  presenting  several  ele- 
vations and  foramina.  Near  its  upper  part  is  an  ovoid,  or  nearly  kidney- 
shaped opening  {fenestra  ovalis),  fig.  389,^  and  fig.  397,  which  leads 
into  the  cavity  of  the  vestibule.  This  opening,  the  long  diameter  of 
which  is  transverse,  with  a slight  inclination  downwards  in  front,  is 
occupied  in  the  recent  state  by  the  base  of  the  stapes,  and  the  annular 
ligament  connected  with  that  process  of  bone.  Above  the  fenestra 
ovalis,  and  between  it  and  the  roof  of  the  tympanum,  is  a transverse 
ridge,  which  corresponds  to  part  of  a bony  canal  {aqueduct  of  Fallo- 
pius), containing  the  portio  dura  of  the  seventh  nerve  : below  it  is  a 
larger  and  more  rounded  elevation,  which  is  caused  by  the  projection 
outwards  of  the  first  turn  of  the  cochlea.  This  projection  is  called  the 
promontory,  or  tuber  cochleae  f it  is  marked  by  several  grooves,  in 
which  lie  the  nerves  of  the  tympanic  plexus  (see  note,  p.  284). 

* Sir  E.  Home  (Philosoph.  Trans,  vol.  xc.  p.  1,  and  cxiii.  p.  23)  and  Meckel  have 
attempted  to  establish  the  fact  of  its  muscularity  ; but  this  conclusion  has  not  met  with  the 
coucurrence  of  other  observers. 

+ It  is  named,  by  Cruveilhier,  the  canal  of  Huguier,  See  his  Anat.  Descript.,  Paris, 
1834,  tom.  iii.  p.  506. 


380 


THE  EUSTACHIAN  TUBE. 


Tlie  grooves  on  the  promontory  extend  between  two  very  small  foramina, 
situate,  the  one  at  the  upper,  and  the  other  at  the  lower  part  of  the  promontory; 
and  these  foramina  open  into  two  small  canals.  The  upper  canal  {canalis  tympa- 
nicus,  Arnold)  extends  through  the  petrous  portion  of  the  temporal  bone,  to  its 
upper  surface,  and  ends  close  to  the  hiatus  Fallopii.  The  lower  canal  leads 
downwards  and  inwards,  also  through  the  substance  of  the  bone,  to  the  base  of 
the  skull,  and  opens  between  the  outer  orifice  of  the  carotid  canal  and  the  fora- 
men lacerum  jugulare. 

Below  and  behind  the  promontory,  and  somewhat  hidden  by  it,  is  a 
roundish,  or,  more  correctly,  a triangular  aperture*  (named  fenestra 
rotunda)^  which  lies  within  a funnel-shaped  depression.  In  the  dried 
bone,  the  fenestra  rotunda  opens  into  the  scala  tympani  of  the  cochlea; 
but,  in  the  recent  state,  it  is  closed  by  a thin  mem.brane, — the  secondary 
membrane  of  the  tympanum  (Scarpa). 

The  posterior  ivall  of  the  tympanum  presents  at  its  upper  part  a 
larger,  and  several  smaller  openings,  fig.  389,^  which  lead  into  irregular 
cavities  {mastoid  cells)  in  the  substance  of  the  mastoid  process  of  the 
temporal  bone.  These  cells  communicate  freely  with  one  another,  and 
are  lined  by  mucous  membrane  continuous  with  that  which  lines  the 
tympanum.  Behind  the  fenestra  ovalis,  and  directed  forwards,  is  a 
small  conical  eminence,  called  the  pyramid,  or  eminentia  papillaris, 
fig.  390,'^.  Its  ,apex  is  pierced  by  a foramen,  from  which  emerges  the 
tendon  of  the  stapedius  muscle.  From  this  foramen  may  be  traced  a 
minute  canal,  which  turns  downwards  in  the  posterior  wall  of  the 
tympanum,  and  joins  obliquely  the  descending  part  of  the  aqueduct  of 
Fallopius.f 

The  anterior  end  of  the  tympanum  gradually  narrows  at  its  lower 
part  towards  the  apertures  of  two  parallel  canals,  which  are  partially 
separated  from  each  other  by  a lamina  of  bone  {processus  cochlearifor- 
mis),  fig.  389,’'.  The  upper  and  smaller  canal,  about  half  an  inch 
long,  lodges  the  tensor  tympani  muscle,  fig.  396,’' ; its  tympanic  orifice 
is  situate  directly  in  front  of  the  fenestra  ovalis,  and  is  surrounded  by 
the  expanded  and  everted  end  of  the  cochleariform  process.  The 
lower  and  larger  of  the  two  canals  forms  the  osseous  portion  of  the 
Eustachian  tube. 

The  Eustachian  tube  (tuba  vel  ductus  Eustachii)  is  a canal,  formed 
partly  of  bone,  partly  of  cartilage  and  membrane,  which  leads  from 
the  cavity  of  the  tympanum  to  the  upper  part  of  the  pharynx.  From 
the  tympanum  it  is  directed  forwards  and  inwards,  with  a little  incli- 
nation downwards  ; and  its  entire  length  is  from  an  inch  and  a half  to 
two  inches.  The  osseous  division  of  the  Eustachian  tube,  fig.  389," 
begins  in  the  lower  and  fore  part  of  the  tympanum,  below  the  cochlea- 
riform process,  and  gradually  contracting  in  diameter  as  it  extends 
forwards,  ends  in  a jagged  opening  at  the  anterior  margin  of  the 
petrous  portion  of  the  temporal  bone,  close  to  the  angle  of  junction 
with  the  squamous  portion.  The  anterior  part  of  the  tube,  fig.  390,’ 
is  formed  of  a triangular  piece  of  cartilage,  the  edges  of  which  are 

* Haller  described  it  as  a canal  having  two  openings,  rather  than  a mere  foramen. 
(“  Elementa  Physiologi®,”  lib.  xv.  § 26.  See  also  Scarpa,  “De  structura  fenestr®  rotunds, 
et  de  tympano  secundario  anatomic®  observationes.”  Mutin®,  1772.) 

t Described  by  Huguier  in  Cruveilhier,  (Anat.  Descript,  tom.  iii.  p.  501.) 


BONES  OF  THE  EAR— MALLEUS. 


381 


slightly  curled  round  towards  each  other,  leaving  an  interval  at  the 
outer  side,  in  which  the  canal  is  completed  by  dense  fibrous  mem- 
brane. Narrow  behind,  the  tube  gradually  expands  till  it  becomes 
wide  and  trumpet-shaped  in  front;  and  the  anterior  part  is  compressed 
from  side  to  side,  and  is  fixed  to  the  inner  plate  of  the  pterygoid  pro- 
cess of  the  sphenoid  bone.  The  anterior  opening  is  oval  in  form,  and 
is  placed  obliquely  at  the  side  and  upper  part  of  the  pharynx,  into 
which  its  prominent  margin  projects  behind  the  lower  meatus  of  the 
nose,  and  above  the  level  of  the  hard  palate.  Through  this  aperture 
the  mucous  membrane  of  the  pharynx  enters,  and  is  continuous  with 
that  which  lines  the  cavity  of  tbe  tympanum. 

2.  SMALL  BONES  OF  THE  EAR. 

Three  small  bones  (ossicula  auditus)  are  contained  in  the  upper  part 
of  the  tympanum,  fig.  390  : of  these,  the  outermost  (malleus)  is  attached 

Fig-.  390. 


\ 


A view  of  the  inner  wait  of  the  tympandm  and  Eustachian  lube  in  the  recent  state,  with  the 
small  hones  in  their  natural  position.  (Arnold.) — 1.  Styloid  process  of  the  temporal  bone.  2. 
Mastoid  process.  3.  Fore  part  of  the  pars  petrosa.  4.  Pharyngeal  portion  of  the  Eustachian  tube. 
6.  Its  cartilaginous  part.  6.  Its  mucous  surface.  7.  Carotid  canal.  8.  Fenestra  rotunda.  9. 
Malleus.  10.  locus.  11.  Stapes.  12.  Pyramid  and  stapedius.  The  suspensory  ligament  of  the 
malleus,  and  the  upper  and  posterior  ligaments  of  the  incus  are  also  seen. 

to  the  membrana  tympani,.fig.  388  ; the  innermost  (stapes)  is  fixed  in 
the  fenestra  ovalis ; and  the  third  (incus),  placed  between  the  other 
two,  is  connected  to  both  by  minute  joints,  fig,  395.  The  first  two 
are  placed  in  nearly  a vertical  direction,  the  last  is  horizontal.  The 
result  is  a species  of  angular  and  jointed  connecting  rod  between  the 
outer  and  inner  walls  of  the  tympanic  cavity,  which  serves  to  com- 
municate vibrations  from  the  membrana  tympani  to  the  fluid  contained 
in  the  vestibule  of  the  internal  ear. 

MALLEUS, 

a.  The  malleus  has  been  named  from  a fancied  resemblance  in  form  to  a 
hammer.  It,  consists  of  a central  thicker  portion,  with  processes  of  different 
lengths.  At  the  upper  end  of  the  bone  is  a rounded  head  (capitulum),  fig.  391,® 


382 


BONES  OF  THE  EAR. 


which  is  lodged  in  the  upper  part  of  the  tympanum,  above  the  membrana 
tympani,  fig.  388,  b;  and  presents  internally  and  posteriorly  an  irregularly  oval 
plane  surface,  fig.  391,  covered  with  cartilage,  for  articulation  with  the  incus. 

[Fig.  391.  Fig.  392.  Fig.  393. 


Fig.  391.  A full  view  of  the  malleus.  1.  Processus  longus  (too  thick).  2.  Processus  brevis. 
3.  The  manubrium.  4.  The  neck.  5.  The  head  of  tlte  malleus ; near  the  figure  is  seen  a small  arti- 
culating face  for  the  incus. 

Fig.  392.  A view  of  the  incus.  1.  Its  body,  with  the  articular  face  for  the  convex  head  of 
the  malleus.  2.  Its  short  or  horizontal  process.  3.  Its  long  or  perpendicular  process.  4,  4.  The 
head  of  this  process  for  articulating  with  the  head  of  the  stapes.  It  is  also  called  the  orbiculare. 

Fig.  393,  A front  view  of  the  stapes.  1,  2.  The  head  of  the  stapes  with  its  articulating  lace 
placed  obliquely.  3.  Its  neck.  4.  Its  anterior  crus.  5.  Its  posterior  crus  more  curved  than  the 
other.  6.  Its  base,  the  part  which  covers  the  fenestra  ovalis. 

Fig.  394.  A magnified  view  of  the  stapes  from  above,  showing  the  fenestrum  in  its  base.  1. 
Cartilaginous  articular  face,  with  the  orbiculare  attached  to  it.  2.  Its  anterior  crus.  3.  Its  poste- 
rior crus.  4,  4.  Its  base  slightly  open; — S.  & H.] 


Below  the  head  is  a constricted  part  or  neck  (cervix),^;  and  beneath  this  another 

slight  enlargemefit  of  the  bone,  to  which  the 
processes  are  attached.  The  handle  (manu- 
brium) of  the  malleus,^  is  a tapering  and 
slightly  twisted  process,  which  is  compressed 
from  before  backwards  to  near  its  point, 
where  it  is  flattened  in  the  opposite  direction. 
The  handle  of  the  malleus  is  directed  nearly 
vertically,  with  a slight  inclination  forwards 
and  inwards,  and  is  received  between  the 
middle  and  inner  layers  of  the  membrana 
tympani,  to  which  it  is  closely  attached.  At 
the  fore  part  and  near  the  base  of  this  pro- 
cess is  a small  elevation,  to  which  the  tensor 
tympani  muscle  is  attached,  fig.  396.  The 
long  process  (processus  gracilis,  fig.  391,') 
is  a very  slender  spine  of  bone,  often  broken 
Ossicles  of  the  left  ear  articulated,  and  off  in  removal  from  the  tympanum,  which 
seen  from  the  outside  and  below,  m.  Head  pjoiects  at  nearly  a right  angle  from  the  neck 
of  the  malleus,  below  which  is  the  con-  of  the  malleus,  and  extends  thence  obliquely 
stnction,  or  neck.  g.  Processus  gracilis,  or  , , ’ „ j ..i,  /-n  ^ ■ 

long  process,  at  the  root  of  which  is  the  downwards  and  forwards  to  the  Glassenan 
short  process,  h.  Manubrium,  or  handle,  fissure.  Its  end  is  flattened  and  expanded, 
sc.  Short  crus;  and  Ic,  long  crus  of  the  and  is  connected  generally  by  ligamentous 
incus.  The  body  of  this  bone  is  seen  ar-  fPjfes  and  sometimes  by  bony  matter  to  the 
t.culatmg  with  the  malleus,  and  its  ^ ^ ^ ^ ^ ^ 

cni8,  through  the  medium  of  the  orbicular  , . i ,,  v „ . '‘V 

process,  here  partly  concealed,  a,  with  the  C6SSUS  bfGVlS  vel  obtUSUS)^  ng.  391^3,  is  alow 
stapes,  s.  Base  of  the  stapes.  Magnified  conical  eminence  springing  from  beneath  i 
three  diameters.  From  Arnold.]  the  cervix,  and  projecting  outwards  towards  I 

the.  upper  part  of  the  membrana  tympani. 
It  is  in  contact  with  the  middle  layer  of  that  membrane,  and  is  not,  therefore,  so 
completely  invested,  as  the  greater  part  of  the  malleus,  by  the  mucous  lining  of 
the  tympanum. 


LIGAMENTS  AND  MUSCLES  OF  TYMPANUM. 


383 


INCUS. 

6.  The  irtcits,  fig.  392,  has  been  compared  to  an  anvil  in  form  (hence  its 
name) ; but  it  perhaps  resembles  more  a bicuspid  tooth  with  the  fangs  widely 
separated.  It  presents  a body  and  two  processes.  The  body  of  the  incus,  ‘,  is 
somewhat  square,  and  is  situate  in  the  upper  and  back  part  of  the  tympanum, 
above  the  margin  of  the  membrana  tympani.  It  presents  a deeply  concave 
articular  surface,  which  is  directed  upwards,  forwards,  and  a little  outwards, 
and  receives  the  head  of  the  malleus.  The  surfaces  of  the  little  ball-and-socket 
joint  thus  formed  are  tipped  with  articular  cartilage  and  covered  by  a synovial 
membrane.  The  shorter  of  the  two  processes  (crus  breve)  of  the  incus,  projects 
nearly  horizontally  backwards  from  the  upper  part  of  the  body  of  the  bone.  The 
end  is  rough,  and  is  often  connected  by  ligamentous  fibres  with  the  posterior 
wall  of  the  tympanum  near  the  entrance  of  the  mastoid  cells.  The  long  process 
(crus  longum),  tapers  rather  more  gradually,  and  is  slightly  bent  as  it  descends 
nearly  vertically  behind  the  handle  of  the  malleus.  On  the  inner  surface  of  its 
point  is  a rounded  tubercle,  tipped  with  cartilage  (processus  lenticularis)  : this 
tubercle,  which  articulates  with  the  head  of  the  stapes,  has  been  described  as  a 
separate  bone,  under  the  name  of  os  orbiculare  seu  lenticulare. 

STAPES. 

The  stapes,  the  third  and  innermost  bone  of  the  ear,  fig.  393,  is  in  shape 
remarkably  like  a stirrup  (whence  its  name),  and  is  composed  of  a head,  a base, 
and  two  crura.  The  head,  is  directed  outwards  towards  the  membrana  tympani, 
and  has  on  its  end  a slight  depression,  covered  with  cartilage,  which  articulates 
with  the  lenticular  process  of  the  incus.  The  base,°,  is  placed  horizontally  in  the 
fenestra  ovalis,  to  the  margin  of  which  it  is  fixed  by  ligamentous  fibres.  The 
form  of  the  base  (fig.  394)  is  irregularly  oval,  the  upper  margin  being  curved,  while 
the  lower  one  is  nearly  straight.  The  crura  of  the  stapes  diverge  from  a constricted 
part  (necAj)  of  the  bone,  immediately  behind  the  head,  and  are  attached  to  the 
outer  suriace  of  the  base  near  its  extremities.-  The  anterior  crus  is  the  shorter 
and  straighter  of  the  two.  The  crura,  with  the  base  of  the  stapes,  inclose  a small 
triangular  space,  which  in  the  recent  state  is  occupied  by  a thin  membrane, 
stretched  across.  A shallow  groove  runs  round  the  opposed  surfaces  of  the  bone, 
and  into  this  the  membrane  is  received. 

3.  LIGAMENTS  AND  MUSCLES  OF  THE  TYMPANUM. 

The  small  bones  above  described  are  connected  with  each  other, 
and  attached  to  the  walls  of  the  tympanum,  by  ligamentous  fibres,  in 
such  a manner  as  to  admit  of  a certain  degree  of  movement  at  each 
of  the  points  at  which  two  bones  come  into  contact.  By  this  means 
apparently  the  vibrations  of  the  membrana  tympani  are  transmitted  to 
the  internal  ear  without  that  sudden  shock  which  would  be  inevitable 
were  the  bony  communication  rigid  and  unyielding. 

With  regard  to  the  connexion  between  the  several  bones  of  the 
tympanum,  it  has  already  been  said  that  the  head  of  the  malleus  is 
received  into  a cup-shaped  depression  in  the  body  of  the  incus,  and 
that  the  lenticular  process  of  the  incus  articulates  with  the  head  of  the 
stapes.  The  surfaces  of  bone  entering  into  the  formation  of  these 
small  joints  are  tipped  with  cartilage,  covered  by  synovial  membrane, 
and  surrounded  by  short  ligamentous  fibres  in  the  form  of  capsular 
ligaments. 

The  attachment  of  the  bones  of  the  ear  to  the  walls  of  the  tympanum 
is  effected  partly  by  the  reflections  of  the  mucous  membrane  lining  that 
cavity,  but  chiefly  by  ligaments  and  muscles.  Owing  to  the  minute- 
ness of  these  structures,  and  their  being  covered  by  vascular  mucous 


384 


MUSCLES  OF  THE  TYMPANUM. 


membrane,  it  is  difficult  to  recognise  with  certainty  their  exact  nature; 
and  hence  much  difference  of  opinion  existsa  mongst  authors  as  to  the 
number  of  the  muscles  of  the  tympanum.  Soemmerring  * describes 
four;  Toddf  increases  the  number  to  nine  ; but  the  general  tendency 
of  modern  anatomical  investigations  is  to  throw  doubts  on  the  muscu- 
lar nature  of  two  or  three  of  those  even  mentioned  by  Soemmerring. 

The  greater  number  of  these  structures  (muscular  and  ligamentous) 
are  attached  to  the  malleus. 


Tmsor  tympani,  fig.  396,’  (musculus  intemus  mallei). — This  is  the  only  muscle 
of  the  tympanum  concerning  the  nature  of  which  there  is  no  dispute.  It  consists 

- of  a long,  tapering,  fleshy  part,  and 


Fig.  396. 


a slender  tendon.  The  muscula" 
fibres  arise  from  the  cartilaginous 
end  of  the  Eustachian  tube  and  the 
adjoining  surface  of  the  sphenoid 
bone,  and  from  the  sides  of  a small 
canal,  already  described,  above  and 
parallel  to  the  osseous  portion  of  the 
Eustachian  tube.  In  this  canal  the 
muscle  is  conducted  nearly  horizon- 
tally backwards  to  the  fore  part  of 
the  cavity  of  the  tympanum.  Imme- 
diately in  front  of  the  fenestra  ovalis 
the  tendon  of  the  muscle  bends  at 
nearly  a' right  angle  over  the  pro- 
cessus cochleariformis,  and  passes 
thence  outwards  to  be  inserted  into 
the  fore  part  of  the  handle  of  the 
malleus,  near,  its  root  and  below  the 
processus  gracilis. 

The  laxator  tympani  major  of  Soem-^ 
merring  is  by  many  anatomists  be- 
lieved to  be  fibrous  tissue  covered 
by  mucous  membrane,  and  supplied 
. with  vessels  which  give  it  somewhat 
the  appearance  of  muscular  structure 
Under  the  idea  that  it  is  sim.ply 
fibrous,  this  has  been  named  the 
anterior  ligament  of  the  malleus.  Arising 
from  the  spinous  process  of  the  sphe- 
A view  of  the  contents  of  the  tympanum  seen  noid  bone,  and  slightly  from  the  car- 
from  above,  after  cutting  away  the  root  of  the  cavity  tilaginous  part  of  the  Eustachian 
arrd  part  of  the  pars  petrosa  of  the  temp^^^^  directed  backwards  and 

1.  Inner  semicircular  canal  opened.  Z.  Cochlea  . t i ..i.  m 

exposed.  3.  Eustachian  tube.  4.  Caput  mallei.  5.  mwards,  passes  through  the  Glas- 
Incus.  6.  Stapes.  7.  Tensor  tympani.  8.  Stape-  serian  fissure,  and  is  inserted  into 
dius.  the  neck  of  the  malleus,  just  abme 

the  root  of  the  processus  gracilis. 

The  laxator  tympani  minor  of  Scemmerring  {posterior  ligament  of  the  malleus— - 
Lincke)  is  made  up  of  reddish  fibres;  which  are  fixed  at  one  end  to  the  upper  and 
back  part  of  the  external  auditory  meatus,  pass  forwards  and  inwards  between  the 
middle  and  inner  layers  of  the  membrana  tympani,  and  are  inserted  into  the  outer 
border  of  the  handle  of  the  malleus,  and  the  short  process  near  it- 

The  suspensory  ligament  of  the  malleusX  (ligamentum  teres  vel  superius)  consists 
of  a little  round  bundle  of  fibres,  which  descend  perpendicularly  from  the  rooi  ol 
the  tympanum  to  the  head  of  the  malleus.  It  is  about  two  lines  in  length. 


* Soemmerring,  S.  T.  leones  Organi  Audiths  Humani.  ■ o r j iquo 

+ Todd,  D.  The  Anatomy  and  Physiology  of  the  Organ  of  Hearing,  &.c.  Lond.  lWd-<. 
t Seen  in  fig.  390,  over  number  9. 


VESSELS  AND  NERVES  OF  THE  TYMPANUM. 


385 


The  incus  has  no  muscles  attached  to  it.  This  bone  is  kept  in 
position  chiefly  by  its  attachments,  already  noticed,  with  the  malleus 
and  stapes. 

It  is  likewise  suspended  by  a small  ligament  (the  posterior  ligament  of  the  incus, 
fig.  390),  which  extends  from  near  the  point  of  the  short  crus  directly  backwards 
towards  the  posterior  wall  of  the  tympanum,  where  it  is  attached  to  the  side  of 
the  pyramid,  near  the  entrance  to  the  mastoid  cells.  Arnold  moreover  describes 
an  upper  ligament  of  the  incus,  fig.  390,  which  attaches  the  upper  part  of  the 
incus  (near  its  articulation  with  the  malleus)  to  the  roof  of  the  tympanum.  Its 
direction  is  parallel  with,  and  close  behuid  the  suspensory  ligament  of  the 
malleus. 

The  stapes  is  provided  with  a little  muscle  which  acts  on  the  outer 
end  or  head,  and  a ligament  which  fixes  the  base  in  such  a manner  as 
to  permit  a limited  degree  of  motion  of  the  whole  bone. 

The  stapedius  muscle,  fig.  396,®  is  lodged  in  the  hoUow  of  the  pyramid,  from  the 
sides  of  which  its  fibres  arise.  The  tendon  pierces  the  aperture  at  the  apex  of 
that  little  elevation,  and  passing  forwards,  is  inserted  into  the  neck  of  the  stapes, 
close  behind  the  articulation  of  that  bone  with  the  lenticular  process  of  the  incus. 
The  muscularity  of  the  stapedius  has  been  questioned  by  some  anatomists. 
Soemmerring  figures  a branch  of  the  portio  dura  supplying  it.  A very  slender 
spine  of  bone  has  been  found  occasionally  in  the  tendon  of  the  stapedius  in  m^an ; 
and  a similar  piece  of  bone,  though  of  a rounder  shape,  exists  constantly  in  the 
horse,  the  ox,  and  other  animals. 

The  annidar  ligament  of  the  stapes  (ligamentum  orbiculare  vel  annulare  baseos 
stapedis)  connects  the  base  of  the  bone  to  the  margins  of  the  foramen  (fenestra 
ovalis),  in  which  it  is  lodged.  The  fibres,  of  the  ligament  are  covered  on  the 
outer  side  by  the  mucous  lining  of  the  tympanum-,  and  on  the  inner  side  by  the 
membrane  of  the  vestibule. 

4.  THE  LINING  MEMBRANE  OF  THE  TYMPANUM. 

The  tympanum  is  lined  throughout  by  a thin,  vascular,  fibro-mucous 
membrane,  which  is  continuous  with  the  mucous  membrane  of  the 
pharynx  through  the  Eustachian  tube,  and  is  further  prolonged  from 
the  tympanum  backwards  into  the  mastoid  cells.  It  adheres  closely 
to  the  walls  of  the  cavity,  forms  the  inner  layer  of  the  membrana 
tympani,  assists  in  covering  over  the  fenestra  rotunda,  and  gives  a 
more  or  less  complete  investment  to  the  bones  and  muscles  of  the 
tympanum,  and  to  the  nerves  which  cross  that  cavity.  The  mucous 
membrane  which  lines  the  cartilaginous  part  of  the  Eustachian  tube 
resembles  much  the  membrane  of  the  pharynx,  with  which  it  is  imme- 
diately continuous.  It  is  thick,  villous,  and  highly  vascular,  covered 
with  vibratile  cilia,  and  provided  with  many  simple  mucous  glands 
w'hich  pour  out  a thick  secretion.  In  the  osseous  part  of  the  Eustachian 
tube,  however,  this  membrane  gradually  changes  its  character;  and  in 
the  tympanum  and  mastoid  cells  it  is  paler,  thinner,  and  less  vascular, 
presents  no  traces  of  mucous  follicles  or  cilia,  and  secretes  a less 
viscid,  yellowish  fluid. 

5.  VESSELS  AND  NERVES  OF  THE  TYMPANUM. 

The  arteries  of  the  tympanum,  though  very  small,  are  numerous, 
and  are  derived  from  several  branches  of  the  external  and  internal 
carotid. 


VOL.  II. 


33 


386 


THE  INTERNAL  EAR. 


The  fore  part  of  the  cavity  is  supplied  chiefly  by  the  tympanic  branch  of  the  internal 
maxillary,  wliich  enters  by  the  fissure  of  Glasser.  The  back  part  of  the  cavity, 
including  the  mastoid  cells,  receives  its  arteries  from  the  stylo-mastoid  branch  of 
the  posterior  auricular  artery,  which  is  conducted  to  the  tympanum  by  the  aque- 
duct of  Fallopius.  These  two  arteries  also  form  a vascular  circle  round  the 
margin  of  the  membrana  tympani.  The  smaller  anastomosing  arteries  of  the 
tympanum  are,  the  petrosal  branch  of  the  middle  meningeal,  which  enters  through 
the  hiatus  Fallopii;  the  Vidian  branch  of  the  descending  palatine,  through  the 
Vidian  canal;  branches  through  the  bone  from  the  internal  carotid  artery,  fur- 
nished from  that  vessel  whilst  in  the  carotid  canal;  and  occasionally  a twig 
along  the  Eustachian  tube  from  the  ascending  pharyngeal  artery. 

The  veins  of  the  tympanum  pour  their  contents  through  the  middle 
meningeal  and  pharyngeal  veins,  and  through  a plexus  near  the  articu- 
lation of  the  lower  jaw,  into  the  internal  jugular  vein. 

Nerves. — The  tympanum  contains  several  nerves;  for,  besides  those 
which  supply  the  parts  of  the  middle  ear,  there  are  several  which 
merely  serve  to  connect  nerves  of  different  origin. 

The  lining  membrane  of  the  tympanum  is  supplied  by  filaments 
from  the  plexus  (tympanic  plexus),  which  occupy  several  small  and 
shallow  grooves  described  as  being  on  the  inner  wall  of  the  cavity, 
and  particularly  on  the  surface  of  the  promontory,  (see  page  284.) 

The  tympanic  plexus  is  formed  by  the  communications  between,  1st,  the  tympanic 
branch  (jierve  of  Jacobson)  from  the  petrous  ganglion  of  the  glosso-pharyngeal;  2d, 
a filament  from  the  carotid  plexus  of  the  sympathetic;  3d,  a branch  which  joins  the 
great  superficial  petrosal  nerve,  from  the  Vidian;  4th  and  lastly,  the  small  superficial 
petrosal  nerve,  from  the  otic  ganglion. 

These  nerves  having  been  already  described  with  the  trunks  from  which  they 
are  severally  derived,  it  is  only  necessary  to  indicate  them  here  as  they  are  seen 
in  the  tympanum.  The  nerve  of  Jacobson,  fig.  359,^  enters  the  tympanum  by  a 
small  foramen  near  its  floor,  which  forms  the  upper  end  of  a short  canal  in  the 
petrous  portion  of  the  temporal  bone,  beginning  at  the  base  of  the  skull  between 
the  carotid  foramen  and  the  jugular  fossa.  The  nerve  from  the  carotid  plexus,® 
is  above  and  in  front  of  this,  and  passes  through  the  bone  directly  from  the 
carotid  canal.  The  branch  to  the  great  superficial  petrosal  nerve,®  is  lodged  in  a 
canal  which  opens  on  the  inner  wall  of  the  tympanum  in  front  of  the  fenestra 
ovalis.  The  small  superficial  petrosal  nerve,®  also  enters  at  the  fore  part  of  the 
cavity  beneath  the  canal  for  the  tensor  tympani. 

The  tensor  tympani  muscle  receives  its  nerve  from  the  otic  ganglion, 
fig.  359,®“;  and  the  stapedius  is  figured  by  Smmmerring  as  supplied  by 
a filament  from  the  facial  nerve.  The  chorda  tympani  is  not  destined 
for  the  supply  of  any  part  of  the  middle  ear;  it  is  invested  in  a tubu'ar 
reflection  of  the  lining  membrane  of  the  tympanum,  and  its  course 
across  the  cavity  has  been  described,  (see  page  280.) 

C.  THE  INTERNAL  EAR,  OR  LABYRINTH. 

This,  which  is  the  essential  or  sensory  part  of  the  organ  of  hearing, 
is  contained  in  the  petrous  portion  of  the  temporal  bone.  It  is  made 
up  of  two  very  different  structures,  known  respectively  as  the  osseous 
and  the  membranous  labyrinth. 

I.  The  osseous  labyrinth  is  lodged  in  the  cancellated  structure  of  the 
temporal  bone,  and  presents,  when  separated  from  this,  the  appear- 
ance shown  in  the  enlarged  figure  (397).  It  is  incompletely  divided 
into  three  parts,  named  respectively  the  vestibule,  the  semicircular 


THE  OSSEOUS  LABYRINTH. 


387 


canals,  and  the  cochlea.  They  are  lined  throughout  by  a thin  serous 
membrane,  which  secretes  a clear  fluid  (perilymph). 

2.  The  membranous  labyrinth  is  contained  within  the  bony  laby- 
rinth, and,  being  smaller  than  it,  a space  intervenes  between  the  two, 
which  is  occupied  with  the  perilymph  just  referred  to.  This  structure 
supports  numerous  minute  ramifications  of  theteuditory  nerve,  and 
incloses  a liquid  secretion  (endolymph).  The  parts  thus  briefly  noticed 
will  now  be  described  in  detail. 


1.  THE  OSSEOUS  LABYRINTH. 

a.  The  vestibule,  fig.  397,’'  forms  a sort  of  central  chamber  of  the 
labyrinth,  which  communicates  in  front  with  the  cochlea,  behind  with 
the  semicircular  canals,  on  the  outer  side  with  the  cavity  of  the  tym- 
panum, and  on  the  inner  side  with  the  meatus  auditonus  internus. 
The  vestibule  is  irregularly  ovoidal  in  shape,  and  is  slightly  flattened 
or  compressed  from  without  inwards.  The  outer  wall,  which  sepa- 
397.  Fig.  398. 


Fig.  397.  A view  of  the  laby- 
rinlh  of  the  left  ear  of  a foetua  of 
8 months,  as  seen  from  above. — 
Magnified  4 diameters.  ],  2,  3, 
The  cochlea.  1,  1.  Its  first  turn. 
2,  2.  Its  second  turn.  3,  3,  Its 
third  or  half  turn,  and  apex  or 
cupola.  4.  The  fenestra  rotun- 
da. 5.  The  fenestra  ovalis.  6. 
The  groove  around  it.  7,  7.  The 
vestibule.  8,  9,  10.  The  posterior 
semicircular  canal,  with  its  am- 
pulla at  8.  11,  11.  The  superior 
semicircular  canal.  12.  The  exter- 
nal semicircular  canal. — S.  & H.] 
Fig.  398.  An  outline,  of  the 
natural  size,  of  figure  397. 


rates  it  from  the  cavity  of  the  tympanum,  presents  the  fenestra  ovalis," 
already  noticed,  which  is  closed,  in  the  recent  state,  by  the  base  of  the 
stapes  and  its  annular  ligament.  Near  the  upper  part  of  the  inner 
wall  is  an  ovoid  depression,  called  the  fovea  hemielliptica,  fig.  399,  o, 
(sinus  ovatus — Soemmerring) ; and  beneath  this  is  another  rounder  [>it, 
the  fouea  hemispherica,  r,  (sinus  rotundus — Soemmerring).  Between 
the  two  hollows  extends  a transverse  ridge,  which  is  named  the  crista 
vestibuli,  or  eminentia  pyramidalis.  Both  the  ridge  and  the  hemi- 
spherical fossa  are  pierced  with  many  srnall  holes,  which  serve  to 
transmit  branches  of  the  auditory  nerve  from  the  internal  auditory 
meatus.  Behind  the  fovea  hemispherica  is  the  small  oblique  opening 
of  a canal,  a,v  (the  aqueduct  of  the  vestibule,)  which  extends  to  the  poste- 
rior surface  of  the  petrous  portion  of  the  temporal  bone;  it  transmits  a 
small  vein  in  a tubular  prolongation  of  membrane.  At  the  back  part 
of  the  vestibule  are  five  round  apertures,  leading  into  the  semicircular 


388 


THE  COCHLEA. 


canals ; and  at  the  lower  and  fore  part  of  the  cavity  is  a larger  open- 
ing, that  communicates  with  the  scala  vestibuli  of  the  cochlea  {aper- 
tura  scales  vestibuli). 

b.  The  semicircular  canals,  fig.  397, ^ ^ are  three  bony  tubes,  situ- 

ate above  and  behind  the  vestibule,  into  which  they  open  by  five 
apertures,  already  m^ticed.  Each  tube  is  bent  so  as  to  form  the 
greater  part  of  a circle ; and  each  presents,  at  one  end,  a slightly 
dilated  part,  called  the  ampulla.  In  other  respects,  namely,  in  posi- 
tion with  regard  to  the  vestibule,  in  direction,  and  in  length,  the  canals 
differ  from  one  another.  The  superior  semicircular  canal,  fig.  397,“ 
is  vertical  in  direction  ; and,  rising  above  any  other  part  of  the  laby- 

Fig.  400. 


Fig.  399.  Interior  of  the 
osseous  labyrinth.  V.  Vesti- 
bule. a,  V.  Aqueduct  of  th'r> 
vestibule,  o.  Fovea  hetniel- 
liptica.  T.  Fovea  hemisphe- 
rica.  S.  Semicircular  canals, 
s.  Superior,  p.  Posterior,  t. 
Inferior,  a,  a,  a.  The  am- 
pullar extremity  of  each.  C. 
Cochlea,  ac.  Aqueduct  of  the 
cochlea,  sit.  Osseous  zone  of 
the  lamina  spiralis,  above  which  is  the  scala  vestibuli,  communicating  with  the  vestibule,  st. 
Scala  tympani  below  the  spiral  lamina.  From  Soemmerring. 

Fig.  400.  Osseous  labyrinth  of  the  barn  owl  (Strix  flamrnea.)  (From  Breschet.) — 1.  Semicir- 
cular canals.  2.  Vestibule.  3.  Cochlea. 

rinth,  forms  a smooth  round  projection  on  the  upper  surface  of  the 
petrous  portion  of  the  temporal  bone.  The  anterior  or  dilated  end  of 
the  canal  opens  by  a distinct  orifice  into  the  upper  part  of  the  vesti- 
bule; whilst  the  opposite  extremity  joins  the  corresponding  non-dilated 
end  of  the  posterior  vertical  semicircular  canal,  and  enters  by  a com- 
mon aperture  with  it  into  the  back  part  of  the  vestibule.  The  poste- 
rior semicircular  canal,  fig.  397,®  also  vertical  in  direction,  is  the 
longest  of  the  three  tubes.  The  ampulla  of  this  canal  is  attached  to 
the  lower  and  back  part  of  the  vestibule ; and  the  cylindrical  crus 
joins  the  common  trunk  above  described.  The  external  semicircular' 
canal,  fig.  397, is  placed  horizontally,  and  opens  by  two  distinct  ori- 
fices into  the  upper  and  back  part  of  the  vestibule.  This  canal  is 
shorter  than  either  of  the  other  two. 

c.  The  cochlea,  tig.  397,^“®  is  the  third  and  most  anterior  division 
of  the  internal  ear.  When  the  dense  bony  substance,  in  which  it  lies; 
embedded,  is  picked  away,  the  cochlea  presents  the  form  of  a blunt 


Fig.  399. 


THE  COCHLEA. 


389 


cone,  the  base  of  which  is  turned  towards  the  internal  auditory  mea- 
tus, whilst  the  apex  is  directed  outwards,  with  an  inclination  forwards 
and  downwards.  The  surface  of  the  cone  is  marked  by  a spiral 
groove,  which  gives  to  this  part  of  the  labyrinth  somewhat  the  ap- 
pearance of  a spiral  shell — whence  its  name. 

A general  idea  of  the  plan  on  which  this  more  complex  portion  of  the  laby- 
rinth is  constracted,  may  be  obtained  by  first  supposing  it  to  be  a gradually 
tapering  bony  tube  of  a certain  length,  which  is  divided  into  two  compartments 
by  a partition  (partly  bone  and  partly  membrane),  the  two  compartments  being 
distinct,  except  at  tne  end,  where  they  communicate  one  with  the  other  in  con- 
sequence of  the  deficiency  of  the  partition.  Such  is  the  simplest  idea  of  this 
division  of  the  internal  ear,  and  it  actually  exists  in  this  form  in  the  ear  of  birds. 
See  fig.  400,®. 

The  names  given  to  certain  parts  may  be  indicated  here.  The  partition  is 
called  the  lamina  spiralis,  and  the  reason  for  the  term  “ spiral”  will  presently 
appear ; the  two  half-tubes,  which  are  termed  scalse,  are  distinguished  by  the 
addition  of  the  names  of  the  cavities  (tympanum  and  vestibule)  into  or  towards 
which  they  open  respectively;  the  place  at  which  the  half-tubes  join  is  the  heli- 
cotrema,  and  the  end  of  the  tube  covering  this  over  is  the  cupola. 

In  order  to  convert  the  straight  tube  no\y  noticed  into  the  spiral  one  named 
cochlea,  it  must  be  supposed  to  be  coiled  on  itself  so  as  to  intercept  a conical 
space — the  first  turn  making  much  the  widest  sweep,  fig.  397 ; and  this  space  is 
occupied  by  the  spongy  substance  of  the  temporal  bone.  The  added  bony  mat- 
ter, which  supports  the  coils  of  the  tube,  together  with  the  inner  surface  of  the 
tube  itself,  constitutes  what  is  called  the  modiolus. 

The  spiral  canal  of  the  cochlea  (canalis  spiralis  cochleae),  fig.  401,®^ 
is  about  an  inch  and  a half  long,  and  about  the  tenth  of  an  inch  in 
diameter  at  the  broadest  part,  which  is  turned  towards  the  cavity  of 
the  vestibule.  From  this  point  the  canal  makes  two  turns  and  a half 
round  the  central  pillar,  (from  left  to  right  in  the  right  ear,  and  in  the 

Fig.  401.  Fig.  402. 


Fig.  401.  Diagram  showing  the  form  and  structure  of  the  dry  cochlea  (laid  open.) — 1.  Medio- 
Ills.  2.  Lamina  spiralis.  3.  Scala  tympani.  4.  Scala  vestibuli. 

Fig.  402.  Seclion  of  the  cochlea.  (From  Arnold.) — 1.  Foramen  cenirale  modioli.  2.  Lamina 
spiralis  ossea.  3.  Scala  tympani.  4.  Scala  vestibuli.  5.  Cellular  substance  of  ihe  modiolus. 

opposite  direction  in  the  left  ear,)  and  ends  by  an  arched  and  closed 
extremity  called  the  cupola,  which  forms  the  apex  of  the  whole 
cochlea.  The  first  coil,  being  composed  of  the  largest  poriion  of  the 
tube,  nearly  hides  the  second  turn  from  view  : and,  bulging  somewhat 
into  the  tympanum,  forms  the  round  elevation  on  the  inner  wall  of 
that  cavity,  called  the  promontory. 

The  modiolus  (columella  cochleas),  fig.  401,^  forms  the  central  pillar 
or  axis  round  which  turn  the  spiral  canal  and  the  spiral  lamina.  It  is 
much  thicker  within  the  first  turn  of  the  cochlea  than  at  any  other 
part ; rapidly  diminishes  in  size  through  the  second  coil ; and  again 

33* 


390 


LINING  MEMBRANE  OF  THE  OSSEOUS  LABYRINTH. 


sliglitly  expands  within  the  last  half-turn  or  cupola,  fig.  401.  The 
outer  surface  of  the  modiolus  is  dense,  being,  in  fact,  composed  of  the 
walls  of  the  spiral  canal ; but  the  centre  is  soft  and  spongy,  and  is 
pierced  by  many  small  canals  for  the  passage  of  ihe  auditory  nerve 
from  the  inner  meatus  to  the  lamina  spiralis,  fig.  402.  One  of  these 
canals,  larger  than  the  rest  {canalis  centralis  modioli),  runs  from  the 
base  through  the  centre  of  the  modiolus  to  the  apex,  where  it  expands 
slightly,  and  forms  what  has  been  named  the  infundibulum. 

The  spiral  lamina  (lamina  spiralis),  fig.  402,  is,  in  the  dried  state, 
a thin,  flat,  osseous  plate,  growing  from  and  winding  round  the  modi- 
olus, and  projecting  into  the  spiral  canal,  so  as  partially  to  divide  it 
into  two  seal®.  In  this  state  the  separation  of  the  seal®  is  incom- 
plete ; firstly,  because  the  osseous  lamina  is  deficient  at  the  apex  of 
the  cochlea,  where  it  forms  a sort  of  open  hook-like  termination 
{hamulus) ; and,  secondly,  because  its  free  margin  does  not,  at  any 
part,  reach  much  further  than  about  two-thirds  of  the  distance  be- 
tween the  modiolus  and  the  outer  wall  of  the  spiral  canal.  This  free 
edge  of  the  osseous  lamina  gives  attachment  in  the  recent  state  to  a 
membranous  septum  (membranous  zone),  which  is  continued  out- 
wards to  be  inserted  into  the  circumference  of  the  spiral  canal. 
Within  the  attached  portion  of  the  osseous  lamina,  and  therefore 
winding  close  round  the  m.odiolus,  is  a small  canal,  named  by  Rosen- 
thal the  canalis  spiralis  modioli. 

The  osseous  lamina  is  thin  and  dense  near  its  free  margin;  but 
near  the  modiolus  it  is  composed  of  two  denser  outer  plates,  inclosing 
a more  open  and  spongy  structure,  in  which  run  numerous  small 
canals,  continuous,  but  running  at  right  angles  with  the  Canals  in  the 
centre  of  the  modiolus.  In  these  are  lodged  filaments  of  the  auditory 
nerve. 

The  scales  are  the  two  passages  into  which  Ihe  general  canal  of  the 
cochlea  is  divided  by  the  lamina  just  described.  One  of  these,  the 
scala  tympani,  fig.  402,®,  communicates  with  the  cavity  of  the  tym- 
panum by  the  fenestra  rotunda,  which,  in  the  recent  state,  is  closed 
by  the  secondary  membrana  tympani,  and  with  the  scala  vestibuli  by 
an  opening  {helicotrema)  left  at  the  apex  of  the  cochlea,  in  conse- 
quence of  the  deficiency  of  the  lamina  spiralis  in  the  last  half-turn  of 
the  canal.  In  the  wider  part  of  the  tympanic  scala,  and  close  to  the 
fenestra  rotunda,  is  the  orifice  of  a small  canal,  fig.  399,  a,  c {aqiteducius 
cochlea;),  which  extends  downwards  and  inwards  through  the  sub- 
stance of  the  petrous  part  of  the  temporal  bone  to  near  the  jugular 
fossa,  and  transmits  a small  vein.  The  surface  of  the  spiral  lamina 
which  looks  towards  this  scala  is  marked  with  numerous  transverse 
striae. 

The  scala  vestibuli,  fig.  402,*,  (rather  narrower  than  the  scala  tym- 
pani in  the  first  turn  of  the  cochlea,)  opens  freely  into  the  cavity  of 
the  vestibule,  and  communicates,  as  already  described,  with  the  scala 
tympani  at  the  apex  of  the  modiolus.  The  transverse  grooves  on  the 
surface  of  the  lamina  which  is  directed  towards  the  scala  are  less 
marked  than  those  in  the  scala  tympani. 

d.  The  lining  Membrane  of  the  osseous  Labyrinth. — This  is  a thin 


THE  MEMBRANOUS  LABYRINTH. 


391 


fibro-serous  membrane,  which  closely  adheres  to  the  whole  inner  sur- 
face of  the  several  parts  of  the  labyrinthic  cavity  just  described. 
From  the  vestibule  it  is  prolonged  directly  into  the  semicircular  canals, 
the  scala  vestibuli  of  the  cochlea,  and  the  aqueductus  vestibuli ; and 
through  the  opening  of  the  helicotrema  it  is  further  continued  into  the 
scala  tympani  and  aqueductus  cochlem.  It  has,  however,  no  com- 
munication with  the  lining  membrane  of  the  tympanum,  being,  like 
that  membrane,  stretched  across  the  openings  of  the  round  and  oval 
fenestrse.  The  outer  surface  of  the  lining  membrane  of  the  labyrinth 
is  rough,  and  adheres  closely,  like  periosteum,  to  the  bone;  the  inner 
surface  is  pale  and  smooth,  is  covered  with  epithelium  like  that  of  the 
arachnoid,  and  secretes  a thin,  slightly  albuminous  or  serous  fluid. 
This  secretion,  first  described  hy  Cotunnius,  and  hence  known  to 
anatomists  as  the  liquor  Cotunnii,  has  been  called  by  Blainville  the 
perilymph.  It  separates  the  membranous  from  the  osseous  labyrinth 
in  the  vestibule  and  semicircular  canals,  occupies  alone  the  cavities 
of  the  seal®  in  the  cochlea,  and  is  continued  into  the  aqueducts  as  far 
as  the  membrane  lining  these  passages  remains  pervious.* 

2.  THE  MEMBRANOUS  LABYRINTH. 

Within  the  osseous  labyrinth,  and  separated  from  its  lining  mem- 
brane by  the  perilymph,  is  a membranous  structure,  which  serves  to 
support  the  ultimate  ramifications  of  the  auditory  nerve.  In  the 
vestibule  and  semicircular  canals  this  membrane  has  the  form  of  a 
rather  complex  sac,  and  incloses  a fluid  called  the  endolymph:  in  the 
cochlea  the  analogous  structure  merely  completes  the  lamina  spiralis, 
and  is  covered  by  the  membrane  which  lines  the  general  cavity  of  the 
osseous  labyrinth. 

a.  The  part  of  the  membranous  labyrinth  contained  in  the  vestibule 
{membranous  vestibule)  consists  of  two  rounded  portions,  which, 
though  closely  connected  together,  appear  to  be  distinct  sacs.  The 
larger  of  the  two,  the  common  sinus  (sinus  communis  vel  utriculus), 
fig.  403,%  is  of  an  oblong  form,  and  slightly  flattened  from  without 
inwards.  It  is  lodged  in  the  upper  and  back  part  of  the  osseous  ves- 
tibule, and  fills  the  depression  called  the  fovea  hemielliptica.  Oppo- 
site the  crista  vestibuli  several  small  branches  of  the  auditory  nerve 
enter  from  the  foramina  in  the  bone;  and  here  the  walls  of  the 
common  sinus  are  thicker  and  more  opaque  than  elsewhere.  The 
cavity  of  the  common  sinus  communicates  with  that  of  the  mem- 
branous semicircular  canals  by  five  orifices,  and  contains,  besides 
endolymph,  a small  mass  of  calcareous  matter.  The  smaller  ves- 
tibular bag,  named  the  saccule,  fig.  403,’®,  is  more  nearly  spherical 
than  the  common  sinus,  but,  like  it,  is  somewhat  flattened.  The 
saccule  is  situated  in  the  lowmr  and  fore  part  of  the  cavity  of  the 
osseous  vestibule,  close  to  the  opening  from  the  scala  vestibuli  of  the 

* According  to  Breschet  and  Huschke,  the  lining  membrane  of  the  labyrinth  is,  in  foetal 
life,  continuous  with  the  dura  mater  and  arachnoid  of  the  skull ; and  the  aqueducts  in  the 
adult  mark  the  points  of  communication,  nearly  obliterated  by  the  development  of  the  bone 
and  the  gradual  closing  in  of  the  osseous  labyrinth. 


392 


MEMBRANOUS  STRUCTURE  OF  COCHLEA. 


cochlea,  and  is  received  into  the  hollow  of  the  fovea  hemispherica, 
from  the  bottom  of  which  many  branches  of  nerve  enter.  The  sac- 
culus  appears  to  have  a cavity  distinct  from  that  of  the  utricle,  but  is 
filled  with  the  same  thin  and  clear  fluid  (endolymph),  and  contains  a 
similar  cretaceous  body. 

b.  The  membranous  semicircular  canals,  fig.  403,  are  about  one- 
third  the  diameter  of  the  osseous  tubes  in  which  they  are  lodged ; but 
in  number,  direction,  and  general  form  they  so  closely  resemble  the 
bony  canals,  that  a separate  description  is  thus  far  unnecessary.  The 
membranous  canals,  which  are  hollow,  open  into  the  sinus  communis 
by  four  single  orifices,  and  one  which  is  common  to  two  canals. 
They  are  filled  with  the  same  fluid  (endolymph).  The  ampullae  are 
thicker  and  less  translucent  than  the  rest  of  these  tubes,  and  nearly 
fill  their  bony  cases.  That  part  of  each  ampulla  which  faces  the 
concavity  of  the  corresponding  osseous  semicircular  canal  is  free, 
rounded  and  prominent  externally,  and  smooth  on  the  inner  surface; 
whilst  the  opposite  portion  is  flattened,  receives  branches  of  nerves 
and  blood-vessels,  and,  when  opened,  presents  on  its  inner  surface  a 
transverse  projection  {septum  transversum),  which  partially  divides 
the  cavity  into  two. 

The  structure  of  the  walls  of  the  common  sinus,  sacculus,  and  membranous 
semicircular  canals  presents  many  points  of  resemblance.  The  membrane  of 
which  they  are  formed  is  generally  thin  and  semitransparent;  but  it  is  thicker 
and  more  opaque  where  nerves  and  vessels  enter.  On  the  outer  surface  is  a 
layer  of  minutely  ramified  blood-vessels  and  loose  cellular  tissue,  which  some- 
times contains  irregular  deposits  of  pigment-cells.  Next  to  this  vascidar  net- 
work, branches  of  the-  auditory  nerve  are  distributed  in  the  form  of  a distinct 
layer,  within  which  is  fine  cellular  tissue,  with,  according  to  Huschke,  a film  of 
closely  set  nucleated  epithelium-cells.  It  is  doubtful  how  far  the  nervous  layer 
e.xtends  into  the  undilated  portion  of  the  semicircular  canals. 

The  endolymph  (aqua  labyrinth!  membranacei,  vel  humor  vitreus  auris)  is  a 
thin,  limpid  fluid,  contained  in  the  sacculus,  common  sinus,  and  semicircular 
canals,  and  is  immediately  in  contact  with  the  layer  of  epithelium-cells  lining 
these  cavities.  The  endolymph  contains  little  but  water,  and  resembles  closely 
the  perilymph  already  described. 

The  otolithes  (otoconies — Breschet)  are  two  small  rounded  bodies,  contairied, 
the  one  in  the  common  sinus,  and  the  other  in  the  sacculus,  and  composed  of 
particles  of  carbonate  and  phosphate  of  lime  agglutinated  together  by  mucus  and 
animal  matter.  Huschke  describes  the  calcareous  particles  as  distinctly  crystal- 
line, whilst  Mr.  Wharton  Jones  distinguishes  them  as  oval  and  somewhat  pointed 
granules.  These  bodies  are  slightly  attached  to  the  walls  of  the  membranous 
labyrinth  opposite  the  points  of  entrance  of  the  nerves  into  the  common  sinus  and 
sacculus,  but  otherwise  they  float  freely  in  the  endolymph. 

c.  The  membranous  structure  of  the  cochlea  is  very  different  in  its 
constitution  from  the  rest  of  the  membranous  labyrinth,  to  which  it  is 
analogous  only  in  affording  a surface  on  which  the  auditory  nerve 
divides,  in  order  to  be  exposed  to  undulations  of  the  fluid  of  the  in- 
ternal ear.  The  cochlea  is  entirely  filled  with  perilymph;  and  the  nervo- 
membranous  structure  which  constitutes  its  sentient  portion  is  flat, 
and  arranged  in  a spiral  form,  so  as  to  assist,  with  the  osseous  lamina, 
in  separating  the  two  scalae.  The  lamina  spiralis  membranacea 
stretches  across  from  the  free  margin  of  the  osseous  lamina  to  the 
outer  circumference  of  the  spiral  canal.  In  the  first  turn  of  the 
cochlea  it  forms  about  one-third  of  the  breadth  of  the  septum  between 


THE  AUDITORY  NERVE. 


393 


the  scalse;  but  towards  the  apex  of  the  cochlea  the  proportion  betw^een 
the  two  parts  of  the  lamina  is  gradually  reversed,  until,  near  the  heli- 
cotrema,  the  membranous  parts  of  the  lamina  are  left  unsupported  by 
any  plate  of  bone. 

In  the  first  and  second  turn  of  the  cochlea  the  membranous  spiral  lamina  con- 
tains, close  around  the  margin  of  the  osseous  plate,  some  cartilaginous  tissue, 
together  with  particles  of  bone.  This  has  given  occasion  to  Breschet  to  distinguish 
the  zonula  cartilaginea  and  the  zonula  membranacea ; the  former  ending,  like  the 
osseous  lamina,  in  a hook-like  turn  (hamulus  cartilagineus')-,  and  the  latter  expand- 
ing at  its  termination,  as  just  described,  and  forming  the  most  transparent  and 
delicate  part  of  the  septum.  Within  the  membranous  lamina  spiralis  is  a flat- 
tened expansion  of  the  cochlear  branch  of  the  auditory  nerve,  covered  on  the 
upper  surface  by  the  membrane  lining  the  scala  vestibuli,  and  on  the  lower  sur- 
face by  the  membrane  of  the  scala  tympani,  fig.  405.  Between  the  nervous  fila- 
ments, which  wiU  be  presently  described,  are  numerous  scattered  opaque  and 
osseous  granules. 

3.  VESSELS  OF  T&E  LABYRINTH. 

a.  Arteries.  — The  internal  auditory  artery,  a branch  from  the 
basilar,  enters,  together  with  the  auditory  and  facial  nerves,  the  inter- 
nal meatus  of  the  ear,  and  at  the  bottom  of  that  shallow  canal  divides 
into  vestibular  and  cochlear  branches.  The  vestibular  branches  are 
distributed  to  the  common  sinus,  sacculus,  and  semicircular  canals, 
w'ith  the  branches  of  nerve  which  they  accompany  through  the  bony 
foramina.  The  cochlear  branches,  fig.  405,  twelve  or  fourteen  in 
number,  traverse  the  many  small  canals  in  the  modiolus  and  bony 
lamina  spiralis,  and  are  distributed  in  the  form  of  a fine  network  on 
the  membrane  lining  the  two  scalce.  Of  the  two,  the  membrane  of  the 
scala  vestibuli  is  said  to  be  the  more  vascular.  Besides  the  foregoing, 
which  is  the  chief  artery  of  the  internal  ear,  the  stylo-mastoid  branch 
of  the  posterior  auricular,  and  occasionally  the  occipital  artery  (Jones), 
send  twigs  to  the  vestibule  and  the  posterior  semicircular  canal. 

h.  Veins. — The  veins  of  the  cochlea  principally  converge  towards  a 
small  spiral  sinus  which  is  contained  between  the  layers  of  the  mem- 
branous lamina  spiralis,  close  to  its  peripheral  attachment.  The  veins 
of  the  vestibule  and  semicircular  canals  accompany  the  arterial 
branches,  and,  joining  the  circular  sinus  of  the  cochlea  at  the  base  of 
the  modiolus,  pour  their  contents  into  the  superior  petrosal  sinus. 

4.  THE  AUDITORY  NERVE. 

The  special  nerve  of  the  sense  of  hearing  {portio  mollis  paris 
septimi,  nervus  auditorius)  is  the  only  nerve  distributed  to  the  laby- 
rinth, or  internal  ear.  Its  course  from  the  brain  to  the  end  of  the 
internal  auditory  meatus,  and  its  connexion  with  the  facial  nerve  whilst 
in  that  canal,  have  been  described.  At  the  bottom  of  the  meatus  the 
auditory  nerve  comes  in  contact  with  a perforated  plate  of  hone, 
which  assists  in  bounding  the'  cavities  of  the  vestibule  and  cochlea  ; 
and  through  the  perforations  in  this  bone  the  filaments  of  the  nerve, 


394 


THE  AUDITORY  NERVE. 


minutely  divided,  pass  to  their  destination  in  the  internal  ear.  Before 
entering  the  foramina,  the  auditory  nerve  divides  into  an  anterior  and 
a posterior  branch  {cochlear  and  vestibular  nerves)-,  but  there  is  some 
difference  of  opinion  amongst  anatomists  as  to  the  usual  precise  distri- 
bution of  these  two  primary  branches.  Having  traversed  the  shell  of 
bone,  and  entered  the  cavity  of  the  osseous  labyrinth,  the  filaments  are 
grouped  into  fasciculi,  which  correspond  in  number  with  the  several 
parts  of  the  membranous  labyrinth  to  which  they  are  given.  There 
are  six  of  these  fasciculi, — the  common  sinus,  the  sacculus,  the  three 
ampullae  of  the  semicircular  canals,  and  the  cochlea,  receiving  one 
each. 


Fig.  403.  The  labyrinth  of  the  left  ear,  laid  open,  in  order  to  show  its  cavities  and  the  mem- 
branous labyrinth.  After  Breschet.  1.  The  cavity  of  the  vestibule,  opened  from  its  anterior  as- 
pect in  order  to  show  the  three-cornered  form  of  its  interior,  and  the  membranous  labyrinth  which 
it  contains.  The  figure  rests  upon  the  common  saccule  of  the  membranous  labyrinth, — the  sinus 
communis.  2.  The  ampulla  of  the  superior  or  perpendicular  semicircular  canal  (4),  receiving  a 
branch  of  the  vestibular  nerve,  3.  5.  The  ampulla  of  the  inferior  or  horizontal  semicircular 
canal,  receiving  a nervous  fasciculus  from  the  superior  branch  of  the  vestibular  nerve.  6.  The 
termination  of  the  membranous  canal  of  the  horizontal  semicircular  canal  in  the  sinus  communis. 
7.  The  ampulla  of  the  posterior  semicircular  canal  (8).  receiving  a branch  of  the  vestibular  nerve. 
9.  The  common  canal,  resulting  from  the  union  of  the  perpendicular  with  the  posterior  semicir- 
cular canal.  10.  The  membranous  common  canal  terminating  in  the  sinus  communis.  11.  The 
oloconite  of  the  sinus  communis  seen  through  the  membranous  parietes  of  that  sac.  12.  The 
sacculus;  its  otoconite  is  seen  through  its  membranous  parietes.  13.  The  scala  tympani.  14. 
The  eitremity  of  the  scala  tympani  corresponding  with  the  fenestra  rotunda.  15.  The  lamina 
spiralis;  the  figure  is  situated  in  the  scala  vestibuli.  16.  The  opening  of  the  scala  vestibuli  into 
the  vestibule.  17.  The  second  turn  of  the  cochlea.  18.  The  remaining  half  turn  of  the  cochlea; 
19.  The  lamina  spiralis  terminating  in  its  falciform  extremity.  The  dark  space  included  within 
the  falciform  curve  of  the  extremity  of  the  lamina  spiralis  is  the  helicotrema.  20.  The  infundi- 
bulum.— W. 

Fig.  404.  Membranous  labyrinth  of  the  left  side,  with  its  nerves  and  otoliths ; su.  Superior 
semicircular  canal,  with  the  ampulla  and  its  nerve  at  one  end,  and  the  other  end  joined  by  p, 
the  posterior  canal,  to  form  the  common  canal,  i.  Inferior,  or  horizontal  canal,  with  the 
ampulla  and  its  nerve  at  one  end,  and  the  other  entering  the  utriculus  separately,  c.  Powdery 
otolith  seen  through  the  translucent  \vall  of  the  common  sinus,  or  utriculus,  with  the  nerves  dis- 
tributed to  it.  s.  Powdery  otolith  of  the  sacculus  seen  with  its  nerve,  in  a similar  way.  n. 
Cochlear  division  of  the  auditory  nerve  cut  off  where  it  enters  the  cochlea,  d.  Portio  dura  of 
the  seventh  pair  leaving  the  auditory  nerve,  oi  portio  mollis,  to  enter  the  aqueduct  of  Fallopius. 
Magnified.  From  Breschet. — T.  & B.] 


[Fig.  403. 


Fig.  404. 


PRIMARY  DIVISION  OF  THE  NERVE. 


395 


Fig.  405.  Section  of  the  cochlea  (from  Arnold),  showing  the  mode  of  distribution  of  some  of 
the  nerves  and  the  artery  of  the  internal  ear — 1.  Auditory  nerve.  2.  Nerves  in  the  lamina  spi- 
ralis. 3.  Central  nerve  of  the  cochlea.  4.  Nerve  of  the  vestibule.  5.  Internal  auditory  artery. 

Fig.  406.  The  ampullae  of  the  superior  and  external  semicircular  canals  and  part  of  the  com- 
mon sinus,  showing  the  arrangement  of  the  nerves.  {From  Steifensand.) — 1.  Ampulla  of  superior, 
and,  2,  ampulla  of  external  semicircular  canals.  3.  Common  sinus.  4 and  5.  Fork-like  swellings 
ofthe  nerves  to  the  ampullae.  6.  Radiating  end  of  the  nerve  to  the  common  sinus. 

The  nerve  of  the  cochlea,  404,  n,  and  fig.  405,  is  shorter,  flatter,  and  broader 
than  any  of  the  other  nerves  of  the  internal  ear,  and  perforates  the  bone  by  a 
number  of  foramina  at  the  bottom  of  the  internal  meatus,  below  the  opening  of 
the  Fallopian  aqueduct.  These  foramina  are  arranged  in  a shallow  spiral  groove 
{tractus  spiralis  faraminulentus),  which  corresponds  with  the  coils  of  the  canal  of 
the  cochlea ; and  they  lead  into  little  bony  canals,  which  follow  first  the  direction 
of  the  axis  of  the  cochlea,  through  the  modiolus,  and  then  pass  at  right  angles  to 
the  axis,  between  the  plates  of  the  bony  lamina  spiralis.  In  the  centre  of  the 
spiral  groove  above  noticed  is  a larger  foramen,  which  leads  to  the  canalis  cen- 
tralis modioli.  Through  the  central  foramen  and  straight  canal  the  filaments  for 
the  last  half-turn  of  the  lamina  spiralis  and  canal  of  the  cochlea  are  conducted, 
fig.  405,®  whilst  the  first  two  turns  are  supplied  by  filaments,®  which  occupy  the 
smaller  foramina  and  bent  canals. 

—The  greater  number  of  anatomists  (including  Scemmerring,  Arnold,  Craveil- 
hier)  describe  the  cochlear  nerve  as  the  anterior  division  of  the  portio  mollis. 
According  to  Breschet,*  however,  the  auditory  nerve  is  divided  into  two  branches, 
one  of  which  (nerf  auditif  anterieur)  supplies  the  common  sinus  and  ampullae  of 


Primary  Division  of  the  Nerve. — The  nerves  for  the  supply  of  the  common  sinus, 
and  of  the  superior  and  the  external  semicircular  canals,  pass  through  a cluster  of 
foramina  in  the  upper  and  back  part  of  the  perforated  plate  of  bone  at  the  bottom 
ofthe  meatus,  close  behind  the  aperture  of  the  aqueductus  Fallopii,  and  enter  the 
cavity  of  the  vestibule  along  the  ridge  (crista  vestibuli),  between  the  hemiellipti- 
cal  and  hemispherical  depressions.  The  filaments  then  unite  into  a common 
trunk,  fig.  404,  which  afterwards  sends  one  branch  to  the  common  sinus,  a 
second  to  the  ampulla  of  the  external,  and  a third  to  the  ampulla  of  the  superior 
semicircular  canal.  The  fibrils  for  the  sacculus  enter  the  vestibule  by  a smaller 
group  of  foramina,  which  are  situate  below  those  just  described,  and  open  at  the 
bottom  of  the  fovea  hemispherica.  The  nerve  of  the  posterior  semicircular  canal  is 
a long  slender  branch  which  traverses  a small  passage  in  the  bone  behind  the 
foramina  for  the  nerve  of  the  sacculus.  It  enters  the  flattened  side  of  the 
ampuUa. 


Fig.  405. 


396 


THE  JMOSE. 


the  anterior  and  the  external  semicircular  canals,  whilst  the  other  (nerf  auditif 
posterieur)  sends  off'  the  cochlear  nerve,  and  the  nerves  of  the  sacculus  and  pos- 
terior semicircular  canal. 

Ultimate  Distribution  of  the  Branches  of  the  Auditory  Nerve. — In  the  membranous 
vestibule  and  semicircular  canals,  the  nervous  filaments,  deprived  of  the  thicker 
sheath  which  covered  them  whilst  in  the  auditory  meatus,  are  invested  in  a thin 
prolongation  of  the  membranous  labyrinth  itself  (Breschet),  this  being  always 
thicker  at  the  points  at  which  the  nerves  enter.  The  nerves  of  the  common  sinus 
and  saccule  terminate  nearly  in  the  same  manner.  They  perforate  the  membrane 
somewhat  obliquely,  and  forming  a slight  projection  on  the  inner  surface  of  the 
sacs,  divide  at  once  into  a fine  pulpy  network  analogous  to  the  retina  of  the  eye. 
The  network  is  composed  of  radiating  lines  of  nervous  globules  deprived  of  their 
neurilemma  and  supported  on  a fine  vascular  membrane ; it  is  in  close  contact 
with  the  otolithes,  and  is  separated  from  the  endolymph  only  by  a layer  of  epithe- 
lium-cells. 

The  nerves  of  the  semicircular  canals  enter  the  flattened  or  least  prominent  side 
of  the  ampullae,  where  they  each  form  a forked  swelling,  fig.  406,  which  corre- 
sponds with  the  transverse  septum  already  described  in  the  interior  of  the  dilata- 
tion. From  the  forked  swelling  a pulpy  nervous  layer,  deprived  of  neurilemma, 
extends  into  the  transverse  septum  and  over  the  inner  surface  of  the  walls  of  the 
ampulla ; but  it  is  yet  undetermined  how  far  the  nerve  extends  into  the  undilated 
portion  of  the  semicircular  canals. 

The  nerve  of  the  cochlea,  as  it  passes  through  the  modiolus  and  osseous  lamina 
spiralis,  divides  into  minute  cylindrical  branches,  which,  on  entering  the  middle 
or  cartilaginous  zone  becorhe  very  indistinct,  and  are  mixed  up  with  granules 
and  particles  of  osseous  matter.  The  precise  mode  of  their  ultimate  distribution 
is  still  uncertain.  By  Scarpa  they  were  said  to  form  brushes,  and  by  Soemmerring 
a feather-like  arrangement,  of  filaments.  By  Treviranus  they  were  thought  to 
end  in  papillse;  and  according  to  Breschet  they  become  flattened,  anastomose 
together,  and  terminate  in  loops  which  are  surrounded  by  irregularly  scattered 
granules. 


THE  NOSE. 

The  nose  is  the  special  organ  of  the  sense  of  smell;  but  it  has  other 
functions  to  fulfil, — for,  communicating  freely  with  the  cavities  of  the 
mouth  and  lungs,  it  is  concerned  in  respiration,  voice,  and  taste ; and, 
by  means  of  muscles  on  its  exterior,  which  are  closely  connected  with 
the  muscles  of  the  face,  it  assists  in  the  expression  of  the  different 
passions  and  feelings  of  the  mind. 

This  organ  consists  of,  first,  the  anterior  prominent  part,  composed 
of  bone  and  cartilage,  with  muscles  which  slightly  move  the  latter, 
and  two  orifices  {anterior  nares)  opening  downwards;  and,  secondly, 
of  the  two  nasal  fossae,  in  which  the  olfactory  nerves  are  expanded. 
The  narrow  cavities  last  mentioned  are  separated  one  from  the  other 
by  a partition  {septum  narium)  formed  of  bone  and  cartilage:  they 
communicate  at  the  outer  side  with  hollows  in  the  neighbouring  bones 
(ethmoid,  sphenoid,  frontal,  and  superior  maxillary);  and  they  open  | 
backwards  into  the  pharynx  through  the  posterior  nares.  The  parts 
here  indicated  in  connexion  will  now  be  noticed  in  detail. 

* Recherches  anatoniiques  et  physiologiques  sur  I’Organe  de  I’Ouie,  &c.  Paris,  1836.  | 


BONES  AND  CARTILAGES  OF  THE  NOSE. 


397 


1.  BONES  OF  THE  NOSE. 

The  outer  projecting  part  of  the  nose  is  supported  in  part  by  the 
nasal  bones,  and  the  nasal  processes  of  the  superior  maxillary  bones, 
forming  the  bridge  of  the  nose.  The  large  triangular  opening  left  be- 
tween those  bones  has  been  described  (at  vol.  i.  p.  157),  and  the  bones 
which  inclose  the  cavity  of  the  nose  have  also  been  described  (ante, 
vol.  i.  p.  161). 

2.  CARTILAGES  OF  THE  NOSE. 

These  are  the  chief  support  of  the. outer  part  of  the  organ.  They 
occupy  the  triangular  opening  seen  in  front  of  the  nasal  cavity  in  the 
dried  skull,  and  assist  in  forming  the  septum  between  the  nasal  fossm. 
There  are  two  larger,  and  three  smaller  cartilages  on  each  side,  and 
one  central  piece  or  cartilage  of  the  septum. 

The  upper  lateral  cartilages  (cartilagines  laterales  nasi),  fig.  407,' 
and  408,  b,  are  situate  in  the  upper  part  of  the  projecting  portion  of  the 

Fig-  407.  Fig'.  408. 


Fig.  407.  View  of  the  bones  and  cartilages  of  the  outer  nose,  from  the  right  side.  (Arnold.) 
—a.  Nasal  bone.  b.  Nasal  process  of  upper  maxillary  bone.  1.  Right  upper  lateral  cartilage. 
2.  Lower  lateral  cartilage,  its  outer  part.  2*.  Inner  part  of  the  same.  3.  Sesamoid  cartilages. 

Fig.  408.  Front  vie  w of  the  cartilages  of  the  nose.  Above  is  seen  the  outline  of  the  nasal 
bones.— a.  Front  edge  of  the  septal  cartilage,  b,  b.  Lateral  cartilages,  c,  c.  Alar  cartilages,  with 
their  appendages. — After  S(jemmerring. 

nose,  immediately  below  the  free  margin  of  the  nasal  bones.  Each 
cartilage  is  flattened  and  triangular  in  shape,  and  presents  one  surface 
outwards,  and  the  other  inwards  towards  the  nasal  cavity.  The  an- 
terior margin,  thicker  than  the  posterior  one,  does  not  quite  meet  the 
lateral  cartilage  of  the  opposite  side,  but  is  closely  united  with  the 
edge  of  the  cartilage  of  the  septum  ; the  lower  margin  is  connected  by 
fibrous  membrane  with  the  lower  lateral  cartilage;  and  the  posterior 
edge  is  inserted  into  the  ascending  process  of  the  upper  maxilla,  and 
the  free  margin  of  the  nasal  bone. 

The  lower  lateral  cartilages  (cartilagines  alarum  nasi),  fig.  407,  and 
409,®  are  thinner  than  the  preceding,  below  which  they  are  placed,  and 
voL.  II.  34 


398 


CARTILAGES  OF  THE  NOSE. 


are  chiefly  characterized  by  the  curve  which  they  form.  Each  carti- 
lage consists  of  an  elongated  plate,  so  bent  upon  itself  as  to  pass  at 


Fig.  409.  Fig.  410. 


Fig.  409.  View  of  the  cartilages  of  the  nose,  looking  into  the  nostrils  from  below.  (From 
Arnold.) — 2.  Outer  part  of  the  lower  lateral  cartilages.  2*.  Inner  part  of  the  same.  4.  Lower 
edge  of  the  cartilages  of  the  septum. 

Fig.  410.  Osseous  and  cartilaginous  septum  of  the  nose,  seen  from  the  left  side.  (After  Ar- 
nold.)— a.  Nasal  bone.  b.  Superior  maxillary  bone.  c.  Sphenoidal  sinus,  d.  Central  or  perpen- 
dicular plate  of  the  ethmoid  bone.  e.  Vomer.  2*.  Inner  part  of  the  (right)  lower  lateral  cartilage 
of  the  nose.  4.  Cartilage  of  the  septum. 

• 

each  side  of  the  orifice  of  the  nose,  and,  by  this  arrangement,  serving 
to  keep  it  open.  One  portion  supports  and  gives  form  to  the  upper 
part  of  the  ala;  and  the' other  projects  backwards,  and  bounds  the 
nostril  on  the  inner  side.  The  outer  portion  is  somewhat  oval  and 
flattened,  or  irregularly  convex  externally.  Behind,  it  is  attached  to 
the  margin  of  the  ascending  process  of  the  upper  maxilla,  by  tough 
fibrous  membrane,  in  which  are  two  or  three  cartilaginous  nodules 
{cartilag.  minores  vel  sesamoidece) ; above,  it  is  fixed,  also,  by  fibrous 
membrane,  to  the  upper  lateral  cartilage,  and  to  the  lower  and  fore 
part  of  the  cartilage  of  the  septum ; towards  the  middle  line  it  leaves 
a deep  groove,  at  the  bottom  of  which  it  adheres  to  the  opposite  car- 
tilage. The  inner  portion  of  the  low^er  lateral  cartilage, forms  a 
small  part  of  the  columna  nasi,  where  it  projects  below  the  anterior 
angle  of  the  cartilage  of  the  septum.  This  part  of  the  cartilage  of  the 
ala  is  thicker  than  the  rest  of  the  structure,  curls  outwards,  and  ends 
in  a free  rounded  margin,  which  projects  outwards  towards  the  nos- 
trils, fig.  409,*^*.  The  lower  and  most  prominent  portion  of  the  ala  of 
the  nose,  like  the  lobule  of  the  ear,  is  formed  of  cellular  tissue,  unsup- 
ported by  cartilage,  and  covered  by  skin. 

The  cartilage  of  the  septum  (cartilago  septi  narium),  fig.  409,“  and 
410,“  has  a somewhat  triangular  outline,  and  is  thicker  at  the  edges 
than  near  the  centre.  It  is  placed  nearly  vertically  in  the  middle  line 
of  the  nose,  and  completes,  at  the  fore  part,  the  separation  between 
the  nasal  fossm.  The  anterior  margin  of  the  cartilage,  thickest  above, 
is  firmly  attached  to  the  back  of  the  nasal  bones  near  their  line  of 
junction,' ; and  below  this  it  lies  between,  and  is  united  with,  the  fore 


NASAL  FOSS^. 


399 


part  of  the  upper  lateral,  and  the  inner  portions  of  the  lower  lateral 
cartilages.  The  posterior  margin  is  fixed  to  the  lower  and  fore  part 
of  the  central  plate  of  the  ethmoid  bone,*** ; and  the  lower  margin  is 
received  into  a groove  in  the  upper  or  anterior  edge  of  the  vomer.* 

3.  THE  MUSCLES  OF  THE  NOSE. 

These  are  described  with  the  muscles  of  the  face,  with  which  they 
are  associated  in  position,  attachments,  and  function.  They  are  the 
pyramidalis  nasi,  the  levator  labii  superioris  alaeque  nasi,  the  com- 
pressor naris,  the  depressor  alae  nasi,  and  the  levatores  proprii  alae 
nasi  (anterior  et  posterior).  (See  vol.  i.  p.  337.) 

4.  T H E S K I N. 

Over  the  upper  part  and  sides  of  the  nose,  the  skin  is  thin  and 
loosely  connected  with  the  bones  and  cartilages  on  which  it  lies.  Over 
the  lower  lateral  cartilages,  it  gradually  becomes  firmer  and  more 
adherent;  and  in  the  free  part  of  the  alae,  where  it  has  no  extra  sup- 
port, it  is  thick  and  solid.  It  is  here  closely  adherent  to  the  muscles, 
and  incloses  small,  separate,  hard  granules  of  fat.  At  the  free  margin 
of  the  ala  the  skin  is  folded  on  itself,  and  incloses,  with  the  inner  part 
of  the  lower  lateral  cartilage,  and  lower  part  of  the  septum  nasi,  an 
oval  aperture  on  each  side  {naris,  apertura  nasi  externa),  which  leads 
into  the  corresponding  nasal  fossge.  The  skin  of  the  nose  is  studded, 
particularly  in  the  grooves  of  the  aim,  with  numerous  small  openings, 
which  lead  to  sebaceous  follicles.  Within  the  margin  of  the  nostrils, 
there  are  several  short,  stiff,  and  slightly  curved  hairs  (^vibrissce),  which 
grow  from  the  inner  surface  of  the  aim  and  septum  nasi,  up  to  the 
point  at  which  the  skin  is  continuous  with  the  mucous  membrane  lining 
the  cavity  of  the  nose. 

NASALFOSS^. 

The  nasal  fossm,  and  the  various  openings  into  them,  with  the  pos- 
terior nares,  have  been  described  as  they  exist  in  the  skeleton  (see 
ante,  vol.  i.  p.  161),  and  that  description  is  also  generally  applicable  to 
the  nose  in  a recent  state;  but  there  are  certain  difi’erences  i*h  the  form 
and  dimension  of  parts,  which,  as  they  depend  on  the  arrangement  of 
the  lining  membrane,  will  be  noticed  after  the  general  account  to  be 
given  of  that  membrane. 

5.  PITUITARY  OR  SCHNEIDERIAN  MEMBRANE. 

The  cavities  of  the  nose  are  lined  by  a mucous  membrane  of  pecu- 
liar structure,  which  like  the  membrane  that  lines  the  cavity  of  the 
tympanum,  is  almost  inseparably  united  with  the  periosteum  and  peri- 
chondrium, over  which  it  lies;  it  belongs,  therefore,  to  the  class  of 
fibro-mucous  membranes,  and  it  is  highly  vascular.  Named  the 
pituitary  membrane,  it  is  continuous  wuth  the  skin,  through  the  ante- 
rior openings  of  the  nose  ; with  the  mucous  membrane  of  the  pharynx, 

* M.  Cruveilhier  describes  a thin  band  of  this  cartilage,  (“prolongeinent  caudal”)  which 
extends  backwards  and  upwards  in  the  groove  of  the  vomer,  to  be  attached  to  the  rostrum 
of  the  sphenoid  bone.  (Anatomie  Descriptive,  1834,  vol.  iii.  p.  429.) 


400 


PITUITARY  MEMBRANE. 


through  the  posterior  apertures  of  the  nasal  fossae ; with  the  conjunc- 
tiva, through  the  nasal  duct  and  lachrymal  canaliculi;  and  with  the 
lining  membrane  of  the  several  sinuses  which  communicate  with  the 
nasal  fossae.  The  pituitary  membrane,  however,  varies  much  in  thick- 
ness, vascularity,  and  general  appearance  in  these  different  parts,  li 
is  thickest  and  most  vascular  over  the  turbinate  bones  (particularly 
the  inferior),  from  the  most  dependent  parts  of  which  it  forms,  in  front 
and  behind,  projections,  which  increase  the  surface,  and  make  the 
turbinate  bones  appear,  in  the  recent  state,  longer  and  more  prominent 
than  they  are  in  the  skeleton.  On  the  septum  narium,  the  pituitary 
membrane  is  still  very  thick  and  spongy;  but  in  the  intervals  between 
the  turbinate  bones,  and  over  the  floor  of  the  nasal  fossae,  it  is  conside- 
rably thinner. 

The  mucous  lining  membrane  of  the  antrum  of  Highmore,  of  the 
frontal  sinuses,  and  of  the  ethmoidal  and  sphenoidal  cells,  contrasts 
strongly  with  that  which  occupies  the  nasal  fossae,  being  very  thin 
and  pale,  and  wearing  the  appearance  more  of  a serous  than  of  a 
mucous  membrane. 


[Fig.  411. 


The  lining  menibrane  of  the  nose  is  defended  by  a layer  of  epithelium,  which, 
in  the  fore  part  of  the  cavity  is  laminated;  but  which  in  the  rest  of  the  nasal 
fossae,  and  in  the  cavities  which  communicate  with  them,  is  covered  with  vibratile 
cilia.  This  membrane  likewise  contains  a nearly  continuous  layer  of  mucous 
glands,  the  orifices  of  which  are  apparent  on  the  surface,  fig.  412.  The  glands  are 

most  numerous  about  the  middle  and  fore 
part  of  the  nasal  fossse,  and  are  largest  at 
the  back  of  the  septum,  near  the  floor  of 
the  nasal  cavity.  They  are  much  smaller 
and  less  numerous  in  the  membrane  lining 
the  several  cavities,  already  mentioned, 
which  communicate  with  the  nasal  fossae, 
The  vessels  and  nerves  which  ramify  in 
the  pituitary  membrane  will  be  presently 
described. 

The  effect  of  the  pituitary  mem- 
brane on  the  form  and  dimensions  of 
the  nasal  fossae,  before  mentioned,  as 
causing  the  difference  which  exists 
between  those  cavities  in  the  skele- 
ton and  in  the  recent  state,  will  now 


A vertical  section  of  the  middle  part  of 
the  nasal  foss®,  giving  a posterior  view  of 
the  arrangement  of  the  ethmoidal  cells,  &c. 
1.  Anterior  fossae  of  the  cranium.  2.  The 
same  covered  by  the  dura  mater.  3.  The 
dura  mater  turned  up.  4.  The  crista  galli  of 
the  ethmoid  bone.  5.  Its  cribriform  plate. 
6.  Its  nasal  lamella.  7.  The  middle  spongy 
bones.  8.  The  ethmoidal  cells.  9.  The  os 
planum.  10.  Inferior  spongy  bone.  11.  The 
vomer.  12.  Superior  maxillary  bone.  13. 
Its  union  with  the  ethmoid.  14.  Anterior 
parietes  of  the  antrum  highmorianum,  cover- 
ed by  its  membrane.  15.  Its  fibrous  layer. 
16.  Its  mucous  membrane.  17.  Palatine 
process  of  the  superior  maxillary  bone.  18. 
Roof  of  the  mouth  covered  by  the  mucous 
membrane.  19.  Section  of  this  membrane. 
A bristle  is  seen  in  the  orifice  of  the  antrum 
highmorianum. — S.  & H.] 


be  further  adverted  to. 

First : owing  to  the  thickness  of  the 
membrane  in  question,  (which  not  only 
lines  the  walls  of  the  fossse,  but  covers  the 
spongy  bones  on  both  sides,)  the  nasal 
cavity  is  much  narrower  in  the  recent 
state.  (See  flg.  411.)  Secondly,  in  con- 
sequence of  the  prolongations  of  mem- 
brane already  alluded  to,  on  the  free 
margins  of  the  turbinate  bones,  these 
bones,  and  more  particularly  the  lower 
pair,  appear  in  the  recent  state  to  be 
more  prominent  and  longer  in  the  direction 
from  before  backwards,  than  in  the  dried 
skull.  Thirdly,  by  the  arrangement  of  the 
mucous  membrane  round  the  orifices 


BLOOD-VESSELS  OF  THE  NOSE. 


401 


which  open  into  the  nasal  fossEe,  some  of  the  foramina  in  the  bones  are  narrowed 
or  completely  closed. 

In  the  upper  meatus,  the  small  orifices  which  lead  into  the  posterior  ethmoidal 
cells,  and  through  them  into 

the  sphenoidal  sinuses,  are  Fig.  412. 

merely  lined  by  a prolonga- 
tion of  the  thin  mucous 
membrane  which  continues 
into  these  cavities  j but  the 
spheno-palatine  foramen  (of 
the  dried  bones)  is  covered 
over  by  the  Schneiderian 
membrane,  so  that  no  such 
opening  exists  in  the  recent 
nasal  fossae. 

In  the  middle  meatus,  the 
aperture  of  the  infundibulum, 
nearly  hidden  by  an  over- 
hanging fold  of  membrane, 
leads  directly  into  the  ante-  3 
rior  ethmoidal  cells,  and 
through  them  into  the  frontal 
sinus.  Below  and  behind 
this,  the  passage  into  the 
antram  of  Highmore  is  sur- 
rounded by  a circular  fold 
of  the  pituitary  membrane, 

(sometimes  prominent  and  outer  wall  of  the  left  nasal  fossa  covered  with  the 

even  slightly  valvular,)  1-  Frontal  bone.  2.  Nasal  bone. 

1 . , , ° d.  auperior  maxillary.  4.  Sphenoid.  5.  The  upper  spongy 

which  leaves  a nearly  Cir-  hone.  6.  Middle  spongy  bone.  7.  Lower  spongy  bone.  The 
cular  aperture  much  smaller  three  meatuses  of  the  nose  are  seen  below  the  three  last- 
than  the  foramen  in  the  bony  named  bones.  8.  The  opening  of  the  Eustachian  tube, 
meatus. 

In  the  lower  meatus,  the  inferior  orifice  of  the  nasal  duct  is  defended  by  two 
nearly  vertical  folds  of  membrane,  between  which  is  a narrow  slit;  and  the  folds 
are  often  adapted  so  accurately  together  as  to  prevent  even  air  from  passing  back 
from  the  cavity  of  the  nose  to  the  nasal  sac.  The  anterior  palatine  foramina 
(described  at  p.  140,  vol.  i.),  are  in  the  recent  state  generally  closed  by  the  Schneide- 
rian membrane.  Sometimes,  however,  a narrow  funnel-shaped  tube  of  mucous 
membrane  descends  for  a little  distance  into  the  canals,  but  is  closed  before  it 
reaches  the  roof  of  the  palate.*  Lastly,  the  apertures  in  the  cribriform  plate  of 
the  ethmoid  bone  are  likewise  covered  over  by  membrane. 


6.  THE  BLOOD-VESSELS  OF  THE  NOSE. 


The  nose  receives  numerous  branches  from  the  facial,  internal 
maxillary,  and  ophthalmic  arteries,  which  anastomose  very  freely  with 
each  other.  Its  veins  join  the  facial  and  ophthalmic  trunks. 

Arteries. — On  the  outer  surface  of  the  nose,  the  alee  and  columna  nasi  are  sup- 
plied by  the  coronary  artery  of  the  upper  lip  and  the  lateral  nasal, — both  branches  of 
the  facial  artery  (see  vol.  i.  p.  544).  The  sides  and  upper  part  of  the  nose  receive 
branches  from  the  lateral  nasal  ( just  mentioned),  the  nasal  branch  of  the  ophthal- 
mic artery,  which  emerges  above  the  tendo  tarsi  (p.  554),  and  from  the  infraorbital 
artery.  The  ethrhoidal  cells,  frontal  sinuses,  and  roof  of  the  nasal  cavity  receive 
their  blood  from  the  anterior  and  posterior  ethmoidal  branches  of  the  ophthalmic 

* Vesalius,  Stenson,  and  Santorini  believed  that  the  tube  of  membrane,  above  alluded  to, 
opens  generally  into  the  roof  of  the  mouth  by  a little  aperture  close  behind  the  interval 
between  ihe  central  incisor  teeth.  Haller,  Scarpa,  and  more  recently,  Jacobson,  find  that 
in  man  it  is  usually  closed,  and  often  difficult  of  detection.  (See  Cuvier’s  Report  on  a 
paper  by  Jacobson.  “ Annales  du  Museum  d’Hist.  Naturelle  Paris,  1811  ; vol.  xviii., 
p.  412.; 


34* 


402 


OLFACTORY  NERVE. 


arter3'.  The  vascular  membrane  over  the  spongy  bones  and  meatus  of  the  nose 
derives  its  chief  supply  from  the  spheno-palatine  branches  of  the  internal  max- 
illary artery ; and  the  alveolar  artery,  from  the  same  trunk,  sends  twigs  into  the 
antrum  of  Highmore.  The  chief  artery  of  the  septum  springs  also  from  the 
spheno-palatine,  and  anastomoses  in  the  anterior  palatine  canal  with  the  terminal 
branch  of  the  descending  palatine  artery,  which  runs  from  the  soft  palate  into 
the  nose. 

Veins. — From  the  outer  surface  of  the  nose  the  blood  is  returned  principally  by 
radicles  of  the  facial  vein.  Within  the  cavity  of  the  organ,  the  veins,  which  are 
very  much  larger  than  the  arteries,  form  a plexus  between  the  mucous  and 
fibrous  layers  of  the  pituitary  membrane,  particularly  over  the  spongy  bones  and 
the  septum.  Some  of  the  largest  of  these  vessels  make  their  exit  through  the 
spheno-palatine  foramen,  and,  by  means  of  the  alveolar  branch,  join  the  facial 
vein.  Others,  from  the  roof  of  the  nasal  fossae,  ethmoidal  cells  and  frontal  sinuses 
(ethmoidal  veins),  enter  the  orbit,  and  join  the  ophthalmic  vein.  The  veins  of 
die  nose  communicate  freely  with  the  veins  within  the  cavity  of  the  skull  through 
the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone. 

7.  THE  NERVES  OF  THE  NOSE. 

The  nerves  of  the  nose,  like  the  vessels,  are  numerous;  the  largest 
and  most  important  being  that  which  endows  it  with  the  power  of 
receiving  the  impressions  of  smell. 

OLFACTORY  NERVE. 

The  origin  of  this  nerve,  the  passage  of  its  branches  through  the 
cribriform  plate  of  the  ethmoid  bone,  and  the . arrangement  of  these 


[Fig.  413. 


The  olfactory  nerve,  with  its  distribution  on  the  septum  nasi.  The  nares  have  been  divided 
by  a longitudinal  section  made  immediately  to  the  left  of  the  septum,  the  right  nares  being  pre- 
served entire.  1.  The  frontal  sinus.  2.  The  nasal  bone.  3.  The  crista  galli  process  of  the 
ethmoid  bone.  4.  The  sphenoidal  sinus  of  the  left  side.  5.  The  sella  turcica.  6.  The  basilar 
process  of  the  sphenoid  and  occipital  bones.  7.  The  posterior  opening  of  the  right  nares.  8.  The 
opening  of  the  Eustachian  tube  in  the  upper  part  of  the  pharynx.  9.  The  soft  palate,  divided 
through  its  middle.  10.  Cut  surface  of  the  hard  palate,  a.  The  olfactory  peduncle,  b.  Its  three 
roots  of  origin,  c.  Olfactory  ganglion,  from  which  the  fdaments  proceed  that  spread  out  in  the 
substance  of  the  pituitary  membrane,  d.  The  nasal  nerve,  a branch  of  the  ophthalmic  nerve, 
descending  into  the  left  nares  from  the  anterior  foramen  of  the  cribriform  plate,  and  dividing 
into  its  external  and  internal  branch,  e.  The  naso-palaline  nerve,  a branch  of  the  spheno-pala- 
tine ganglion  distributing  twigs  to  the  mucous  membrane  of  the  septum  nasi  in  its  course  to  (/) 
the  anterior  palatine  foramen,  where  it  forms  a small  gangliform  swelling  (Cloquet’s  ganglion)  by 
its  union  with  its  fellow  of  the  opposite  side  g.  Branches  of  the  naso-palatine  nerve  to  the 
palate,  h.  Posterior  palatine  nerves,  t,  i.  The  septum  nasi. — C.] 


NERVES  OF  THE  NOSE. 


403 


branches  after  they  enter,  and  begin  to  divide  in  the  cavity  of  the  nose, 
have  been  already  described  (ante,  pp.  243  and  200).  The  general 
distribution  of  the  outer  and  inner  set  of  branches  is  nearly  similar. 
At  first,  lodged  in  grooves  on  the  surface  of  the  bone,  the  nerves  enter 
obliquely  the  substance  of  the  Schneiderian  membrane,  so  as  to  get 
between  the  mucous  and  fibrous  layers.  Here  they  soon  divide  into 
brush-like  and  flattened  tufts  of  filaments,  which,  spreading  out  laterally, 
and  communicating  freely  with  similar  branches  on  either  side,  form 
a fine  and  close  network,  with  long  and  narrow  intervals  between  the 
points  of  junction.  Whilst  thus  dividing,  the  nerves  are  enveloped  in 
sheaths  of  dura  mater,  prolonged  from  the  foramina  in  the  ethmoid 
bone,  which  makes  them  much  firmer  than  where  they  are  connected 
with  the  olfactory  bulb.  The  nerves  of  the  septum,  fig.  413,  are 
rather  larger  than  those  of  the  outer  wall  of  the  nasal  fossae ; as  they 
descend,  they  become  very  indistinct,  and  are  not  visible  on  the  lower 
fourth  of  the  septum.  The  nerves  of  the  outer  wall,  fig.  355,  are 
divided  into  two  groups; — the  posterior  branches  are  distributed  over 
the  surface  of  the  upper  spongy  bone,  and  the  anterior  branches  descend 
over  the  middle  spongy  bone,  but  are  then  too  small  to  be  traced  even 
round  the  free  margin  of  this  bone.  No  branch  of  the  olfactory  nerve 
has  been  found  in  the  mucous  membrane  over  the  lower  spongy  bones, 
or  the  middle  and  lower  meatus. 

The  smaller  nerves  of  the  nose  have  been  already  fully  described,  and  ^vill, 
therefore,  here  be  merely  enumerated  and  referred  to.  On  the  outer  surface  of 
the  nose  are  distributed  branches  of  the  facial  and  infra-orbital  nerves  (p.  269), 
the  infratrochlear  nerve,  and  a twig  of  the  nasal  branch  of  the  ophthalmic  (p.  266). 
To  the  upper  and  anterior  part  of  the  septum  and  outer  wall  of  the  nasal  fossae 
are  given  other  branches  of  the  nasal  division  of  the  ophthalmic  nerve.  To  the 
upper  and  back  part  of  the  septum,  and  to  the  upper  spongy  bones,  are  distributed 
nerves  derived  from  the  Vidian  nerve  (p.  272),  and  from  the  spheno-palatine 
ganglion  (p.  272).  The  middle  of  the  septum  receives  the  naso-palatine  nerve 
(fig.  413),  as  it  courses  to  the  anterior  palatine  foramen.  The  middle  and  lower 
spongy  bones  are  supplied  by  offsets  from  the  larger  palatine  branch  of  the 
spheno-palatine  ganglion  (fig.  355);  and  lastly,  the  lower  meatus  and  the  lower 
spongy  bone  are  further  furnished  with  little  twigs  from  the  anterior  dental  nerve, 
a branch  of  the  upper  maxillary  (p.  269). 


ORGANS  OF  DIGESTION. 


The  digestive  apparatus  includes  that  portion  of  the  organs  of 
assimilation  within  which  the  food  is  received  and  partially  converted 
into  chyle,  and  from  which,  after  the  chyle  has  been  absorbed,  the 
residue  or  excrement  is  expelled.  It  consists  of  a main  or  primary 
part  named  the  alimentary  canal,  and  of  certain  accessory  organs. 

The  alimentary  canal  is  a long  membranous  tube,  commencing  at 
the  mouth  and  terminating  at  the  anus,  composed  of  certain  tunics  or 
coats,  and  lined  by  a continuous  mucous  membrane  from  one  end  to 
the  other.  Its  average  length  is  about  thirty  feet,  being  about  five  or 
six  times  the  length  of  the  body.  The  upper  part  of  it  is  placed 
beneath  the  base  of  the  skull,  the  succeeding  portion  is  situated  within 
the  thorax,  and  the  remainder  is  contained  within  the  cavity  of  the 
abdomen.  In  these  several  situations,  its  form,  dimensions,  and  con* 
nexions,  its  structure  and  its  functions,  are  so  modified,  that  certain 
natural  subdivisions  of  it,  bearing  different  names,  have  been  recog- 
nised by  all  anatomists. 

It  may  be  considered  as  composed  of  two  parts:  one  situated 
above  the  diaphragm,  and  the  other  below  that  muscular  partition, 
and  therefore  within  the  abdomen.  The  first  division  consists  of  the 
organs  of  mastication,  insalivation,  and  deglutition;  and  comprises  the 
mouth,  the  pharynx,  and  the  oesophagus  or  gullet.  The  second  divi- 
sion consists  of  the  organs  of  digestion  properly  so  called,  and  of  those 
of  defaecation : viz.,  the  stomach,  the  small  intestine,  and  the  great 
intestine. 

The  accessory  parts  are  chiefly  glandular  organs,  which  pour  their 
secretions  into  it  at  different  points.  They  consist  of  the  salivary 
glands  (named  the  parotid,  submaxillary,  and  sublingual),  the  liver, 
and  pancreas.  Besides  these  large  glandular  organs,  a multitude  of 
small  glands,  compound,  follicular  or  tubular,  are  collected  together  at 
certain  points,  or  scattered  over  large  portions  of  the  inner  surface  of 
the  alimentary  canal:  these  will  be  described  with  the  mucous  mem-  , 
brane  of  each  part.  The  remaining  accessory  organs  are  the  teeth, 
theyaujs,  the  tongue,  and  the  spleen. 

THEMOUTH.  , 

The  mouth  (fig.  444)  is  the  space  included  between  the  lips  and  the  ii 
throat  or  fauces.  It  is  bounded  in  front  by  the  lips,  d d,  at  each  side  j| 
by  the  cheeks,  below  by  the  tongue,  b,  and  above  by  the  hard  and  soft  | 
palate,  a and  c;  whilst  behind  it  communicates  with  the  pharynx  at 
3,  through  an  opening  called  the  fauces  (isthmus  faucium).  The 
cavity  of  the  mouth,  with  its  contained  parts  (excepting,  of  course, 
the  teeth),  is  lined  throughout  by  a mucous  membrane,  which  is  of  a 


THE  TEETH. 


405 


pink  rosy  hue  during  life,  but  pale  gray  after  death,  and  which  presents 
peculiarities  of  surface  and  structure  to  be  noticed  hereafter. 

The  lips,  which  bound  the  anterior  aperture  or  rima  of  the  mouth, 
are  composed  of  an  external  layer  of  skin,  and  of  an  internal  layer  of 
mucous  membrane;  between  which  are  found,  besides  muscles,  vessels 
and  nerves,  already  fully  described  in  other  parts  of  this  work,  some 
cellular  tissue,  fat,  and  numerous  small  glands.  The  principal  muscle 
is  the  orbicularis  oris ; but  several  others  are  inserted  into  this  one  at 
various  points,  and  enter  more  or  less  into  the  formation  of  the  lips. 
The  free  border  of  the  lips  is  protected  by  a dry  mucous  membrane, 
which  becomes  continuous  with  the  skin,  is  covered  with  numerous 
minute  papillae,  and  is  highly  sensitive.  On  the  inner  surface  of  each 
lip,  the  mucous  membrane  forms  a fold  in  the  middle  line,  connecting 
the  lip  with  the  gums  of  the  corresponding  jaw.  These  are  the  frcena 
or  frcenula  of  the  lips:  that  of  the  upper  lip  is  much  the  larger  of 
the  two. 

Numerous  small  glands,  called  labial  glands,  are  found  beneath  the 
mucous  membrane  of  the  lips,,  around  the  opening  of  the  mouth. 
They  are  situated  between  the  mucous  membrane  and  the  orbicularis 
oris  muscle.  They  are  compound  glands  of  a rounded  form,  the 
largest  of  them  not  exceeding  the  size  of  a split  pea ; and  they  open 
into  the  mouth  by  distinct  orifices. 

The  cheeks,  like  the  lips,  consist  of  a cutaneous,  a muscular,  and  a 
mucous  layer,  besides  fat,  cellular  tissue,  glands,  vessels,  and  nerves. 
The  principal  muscle  of  the  cheek  is  the  buccinator,  but  the  two  zygo- 
matici,  the  masseter,  the  orbicularis  palpebrarum,  and  the  platysma  in 
part  enter  into  its  formation.  There  is  a remarkable  accumulation  of 
fat  between  the  masseter  and  buccinator  muscles.  Between  the  last- 
named  muscle  and  the  mucous  membrane  are  the  buccal  glands, 
similar  to  the  labial  glands,  but  smaller.  Two  or  three  glands,  larger 
than  the  rest,  found  between  the  masseter  and  buccinator  muscles,  and 
opening  by  separate  ducts  near  the  last  molar  tooth,  are  called  the 
molar  glands. 

The  duct  of  the  parotid  gland  also  opens  upon  the  inner  surface  of 
the  cheek,  opposite  to  the  second  upper  molar  tooth. 

Immediately  behind  the  lips  and  cheek,  are  the  dental  arches,  con- 
sisting of  the  teeth,  gums,  and  maxillae.  The  jaw-bones,  the  articula- 
tion and  movements  of  the  lower  maxilla,  and  the  muscles  used  in 
mastication,  are  elsewhere  described.  The  gums  (gingivae),  which 
scarcely  require  a notice,  are  composed  of  a dense  fibrous  tissue,  con- 
nected very  closely  with  the  periosteum  of  the  alveolar  processes,  and 
covered  by  a red  and  not  very  sensitive  mucous  membrane,  which  is 
smooth  in  its  general  surface,  but  immediately  around  the  teeth  is 
beset  with  fine  papillse. 

THE  TEETH. 

In  the  human  subject,  as  in  mammalia  generally,  two  sets  of  teeth 
make  their  appearance  in  the  course  of  life,  of  which  the  first  consti- 
tutes the  temporary,  deciduous,  or  milk  teeth,  whilst  the  second  is 
named  the  permanent  set.  The  temporary  teeth  are  twenty  in  num- 


406 


GENERAL  CHARACTERS  OF  THE  TEETH. 


ber,  ten  in  each  jaw,  and  the  permanent  set  consists  of  thirty-two,  six- 
teen above  and  sixteen  below.  Deficiencies  in  the  number  of  the  teeth 
sometimes  occur,  but  much  more  frequently  the  number  is  increased  by 
one  or  more  supernumerary  teeth.  These  are  usually  small,  and  pro- 
vided with  only  a single  fang ; and,  though  generally  distinct,  they 
are  sometimes  attached  to  other  teeth : they  occur  more  frequently 
near  the  front  than  the  hinder  teeth,  and  are  more  often  met  with  in 
the  upper  than  in  the  lower  jaw. 

General  Characters  of  the  Teeth. — Though  the  teeth  are  distin- 
guished by  peculiarities  of  external  configuration  into  several  classes, 
they  have  all  certain  characters  in  common.  Thus,  each  tooth  is 
described  as  consisting  of  three  portions,  viz.,  one  which  projects 
above  the  gums  and  is  named  the  body  or  crown, — another  which  is 
lodged  in  the  alveolus  or  socket,  and  constitutes  the  root  or  fang, — 
and  a third,  intermediate  between  the  other  two,  and  from  being  more 
or  less  constricted,  named  the  cervix  or  neck.  The  size  and  form  of 
each  of  these  parts  vary  in  the  different  kinds  of  teeth. 

The  roots  of  all  the  teeth  are  implanted  into  the  alveoli  of  the  jaws, 
and  are  accurately  fitted  to  them,  by  a peculiar  mode  of  union,  called 
gomphosis  (yoixtpos,  a nail).  Each  alveolus  is  lined  by  the  periosteum, 
which  is  also  reflected  on  to  the  contained  fang,  and  invests  it  as  high 
as  the  cervix.  This  dental  periosteum,  sometimes  named  the  perio- 
dontal membrane,  is  blended  with  the  dense  and  slightly  sensitive 
tissue  of  the  gums,  which  closely  surrounds  the  neck  of  the  tooth. 
The  roots  of  all  the  teeth  taper  from  the  cervix  to  the  point,  and  this 
form,  together  with  the  accurate  adjustment  to  the  alveolus,  has  the 
effect  of  distributing  the  pressure  during  use,  over  the  whole  socket, 
and  of  preventing  its  undue  action  on  the  apex  of  the  fang,  through 
which  the  blood-vessels  and  nerves  enter. 

The  thirty-two  permanent  teeth  consist  of  four  incisors,  two  canines, 
four  bicuspids,  and  six  molars,  in  each  jaw.  The  twenty  temporary 
teeth  are  four  incisors,  two  canines,  and  four  molars,  above  and  below. 
There  are  no  bicuspids  among  the  temporary  teeth,  but  the  eight  de- 
ciduous molars  are  succeeded  by  the  eight  bicuspids  of  the  permanent 
set.  The  relative  position  and  arrangement  of  the  different  kinds  of 
teeth  in  the  jaws  may  be  shown  by  the  following  scheme,  which  also 
exhibits  the  relation  between  the  two  sets  in  these  respects : 

MO.  OA.  IN.  OA.  MO. 

( Upper  2 14  12  =10 

Temporary  teeth  . . . . < - 20 

( Lower  2 14  12  =10 

MO.  BI.  CA.  IN.  CA.  BI.  MO. 

( Upper  3 2 1 4 1 2 3 = 16 

Permanent  teeth  . . . . < = 32 

( Lower  3214123  = 16 

Special  Characters  of  the  Permanent  Teeth. — The  incisors,  (fig. 
414,  a,,  b,)  eight  in  number,  are  the  four  front  teeth  in  each  jaw,  and 
are  so  named  from  being. adapted  for  cutting  or  dividing  the  soft  sub- 
stances used  as  food.  Their  croions  are  chisel-shaped,  and  have  a 
sharp  horizontal  cutting  edge,  which,  by  continued  use,  is  bevelled  off 


SPECIAL  CHARACTERS  OF  THE  TEETH. 


407 


behind  in  the  upper  teeth,  but,  in  the  lower  teeth,  is  worn  down  in 
front.  Before  being  subjected  to  wear,  the  horizontal  edge  of  the  in- 
cisor teeth  is  serrated  or  marked  by  three  small  prominent  points  (d). 
The  anterior  surface  of  the  crown  is  slightly  convex,  and  the  poste- 
rior concave  (c).  The  favg  is  long,  single,  conical,  and  compressed 
at  the  sides,  where  it  sometimes  though  rarely  presents  a slight  longi- 
tudinal furrow. 

The  lower  incisor  teeth  are  placed  vertically  in  the  jaw,  but  the 
upper  teeth  are  directed  obliquely  forwards.  The  upper  incisors  are, 
on  the  whole,  larger  than  the  lower  ones.  In  the  upper  jaw  the 
central  incisors  are  larger  than  the  lateral,  whilst  the  reverse  is  the 
case  in  the  lower  jaw,  the  central  incisors  being  there  the  smaller, 
and  being,  moreover,  the  smallest  of  all  the  incisor  teeth. 

The  canine  teeth  (canini,  cuspidati),  four  in  number  (fig.  415),  are 
placed  one  on  each  side,  above  and  below,  immediately  next  to  the 
lateral  incisors.  They  are  larger  and  stronger  than  the  incisor  teeth. 
The  crown  is  thick  and  conical,  convex  in  front  and  hollowed  behind 
{b),  and  may  be  compared  to  that  of  a large  incisor  tooth  the  angles 
of  which  have  been  filed  away,  so  as  to  leave  a single  central  point 
or  cusp  (a),  whence  the  name  cuspidate  applied  to  these  teeth.  The 
point  always  becomes  worn  down  by  use.  The  fang  of  the  canine 
teeth  is  single,  conical,  and  compressed  at  the  sides ; it  is  longer  than 
the  fangs  of  any  of  the  other  teeth,  and  is  so  large  as  to  cause  a cor- 


Fig.  414,  Incisor  teeth  of  the  right  side  of  the  upper  and  lower  jaws. — a.  The  middle  incisors, 
upper  and  lower,  seen  in  front,  b.  The  lateral  incisors,  ditto,  c.  The  middle  incisors,  seen  on 
the  side,  to  show  the  chisel-shape  of  the  crown.  The  fang  of  the  lower  tooth  is  marked  by  a 
slight  groove,  d.  Shows  the  indented  edge  of  the  incisors  before  they  are  subjected  to  wear. 

Fig.  41.5.  Canine  tooth  of  the  upper  jaw,  or  eye-tooth. — a.  Seen  in  front,  b.  Lateral  view  ; 
showing  the  long  fang  grooved  on  the  side. 

Fig.  416.  Bicuspid  tooth  of  the  upper  and  lower  jaw. — a.  Front  view.  b.  Lateral  view,  show- 
ing the  two  cusps  of  the  crown  and  the  groove  on  the  side  of  the  fang,  which  has  become  cleft 
in  the  up^er  tooth. 


Fig.  414. 


Fig.  416. 


408 


SPECIAL  CHARACTERS  OF  THE  TEETH. 


responding  prominence  of  the  alveolar  arch  : on  the  sides  {b)  it  is 
marked  by  a groove,  an  indication,  as  it  were,  of  the  cleft  or  division 
which  appears  in  the  teeth  next  following. 

The  upper  canines,  popularly  called  the  eye-teeth,  are  larger  than 
the  lower,  and  in  consequence  of  this,  as  well  as  of  the  greater  width  of 
the  upper  range  of  incisors,  they  are  thrown  a little  further  outwards 
than  the  lower  canine  teeth.  In  the  dog  tribe,  and  in  the  carnivora 
generally,  these  teeth  acquire  a great  size,  and  are  fitted  for  seizing 
and  killing  prey,  and  for  gnawing  and  tearing  it  when  used  as  food. 

The  bicuspids  (bicuspidati),  (fig.  416,)  also  called  the  small,  false,  or 
premolars,  are  four  in  each  jaw;  they  are  shorter  and  smaller  than 
the  canines,  next  to  which  they  come,  two  on  each  side.  The  crown 
is  compressed  before  and  behind,  its  long  diameter  being  across  the 
jaw;  it  is  convex,  not  only  on  its  outer  or  labial  surface  (a),  like  the 
preceding  teeth,  but  on  its  inner  surface  also,  which  rises  vertically 
from  the  gum  [b) ; its  free  surface,  which  is  therefore  broader  than 
that  of  an  incisor  or  canine  tooth,  is  surmounted  by  two  pointed  tuber- 
cles or  cusps,  of  which  the  external  one  is  larger  and  higher  than  the 
other.  The  fang  is  also  flattened  and  is  deeply  grooved  in  all  cases, 
showing  a tendency  to  become  double.  The  apex  of  the  fang  is  gene- 
rally bifid,  and  in  the  second  upper  bicuspid,  the  root  is  often  cleft  for 
a considerable  distance  {b).  The  upper  bicuspids  are  larger  and 
more  characteristic  in  form  than  the  lower  ones.  Sometimes  the  first 
lower  bicuspid  has  only  one  tubercle  distinctly  marked,  i.  e.,  the  ex- 
ternal, and  in  that  case  approaches  in  figure  to  a canine  tooth. 

The  molar  teeth  (fig.  417),  true  or  large  molars,  or  multicuspid 

Fig.  417. 


j'irst  molar  tooth  of  by  a crucial  depression.  I'he  upper  molars  nave 
lo we rjrw^*^The  crown  cusps  situated  at  the  angles  of  the  masticating 

of  the  upper  molar  has  surface  (see  figure);  of  these  the  internal  and  ante- 
[h^e^'^Tangs'^  The  largest,  and  is  frequently  connected 

crown  of  the  lower  with  the  posterior  external  cusp  by  a low  oblique 

has  five  cusps,  and  its  Ip  the  Upper  wisdom  teeth,  the  two  internal 

toot  two  fangs.  o , , ■ i mi  r .u 

tubercles  are  blended  together.  1 he  crowns  ot  me 


teeth,  are  twelve  in  number,  and  are  arranged  be- 
hind the  bicuspid  teeth,  three  on  each  side,  above 
and  below.  They  are  distinguished  by  the  large 
size  of  the  crown,  and  by  the  great  width  of  its 
grinding  surface.  The  first  molar  is  the  largest, 
whilst  the  third  is  the  smallest,  in  each  range,  so  that 
in  point  of  size  a gradation  is  observed  in  these  1 
teeth.  The  last  molar  in  each  range,  owing  to  its 
late  appearance  through  the  gums,  is  called  the  wis- 
dom tooth,  dens  sapientiae.  The  crowns  of  the  molar 
teeth  are  low  and  cuboid  in  their  general  form. 
Their  outer  and  inner  surfaces  are  convex,  whilst 
they  are  raiher  flattened  before  and  behind.  The 
grinding  surface  is  nearly  square  in  the  lower  teeth, 
and  rhomboidal  in  the  upper,  the  corners  being 
rounded  off : it  is  not  smooth,  but  is  provided  with 
four  or  five  trihedral  tubercles  or  cusps  (whence  the 
name  of  multicuspidati),  separated  from  each  other 


SPECIAL  CHARACTERS  OF  THE  TEETH. 


409 


lower  molars,  which  are  larger  than  those  above,  have  five  cusps,  (see 
figure,)  the  additional  one  being  placed  between  the  two  posterior 
cusps,  and  rather  to -the  outer  side:  this  is  especially  evident  in  the 
lower  wisdom  teeth,  in  which  the  crown  is  smaller  and  rounder  than 
in  the  others.  Hh.e fangs  of  all  the  molar  teeth  are  multiple.  In  the  two 
anterior  molars  of  the  upper  jaw,  they  are  three  in  number,  viz.,  two 
placed  externally,  which  are  short,  divergent,  and  turned  towards  the 
antrum  of  the  superior  maxilla;  and  a third  or  internal  fang,  which  is 
larger  and  longer,  and  is  directed  towards  the  palate.  This  third  fang 
is  often  slightly  grooved,  especially  when  the  two  internal  cusps  are 
very  distinct,  and  sometimes  it  is  divided  into  two.  The  two  anterior 
molars  of  the  lower  jaw  have  each  two  fangs,  one  anterior,  the  other 
posterior,  which  are  broad,  compressed  and  grooved  on  the  faces  that 
are  turned  towards  each  other:  they  have  an  inclination  or  curve 
backwards  in  the  jaw,  and  are  either  slightly  divergent  or  are  nearly 
in  contact  with  each  other ; sometimes  one  or  both  of  them  is  divided 
into  two  smaller  fangs.  In  the  wisdom  teeth  Of  both  jaws  the  fangs 
are  generally  connate  or  collected  into  a single  irregular  conical  mass, 
which  sometimes  shows  traces  of  a subdivision  into  two  fangs  in  the 
lower  teeth,  and  into  three  in  the  upper  teeth : these  connate  fangs  are 
either  directed  backvrards  in  the  substance  of  the  jaw,  or  are  curved 
or  bent  irregularly. 

The  bicuspid  and  the  molar  teeth,  from  the  breadth  of  their  crowns, 
are  fitted  for  bruising,  crushing,  and  grinding  the  food  in  mastication. 

The  entire  set  of  teeth  in  each  jaw  forms  an  even  curve  or  arch, 
which  is  not  broken  by  any  intervals,  as  is  the  case  in  the  dental  appa- 
ratus of  many  animals,  even  in  the  Quadrumana.  The  upper  dental 
arch  is  rather  larger  than  the  lower  one,  so  that  the  teeth  of  the  upper 
jaw  slightly  overhang  the  lower  set.  This  is  owing  principally  to  the 
fact  that  the  lower  teeth  are  placed  either  vertically,  as  in  front,  or 
are  set  so  as  to  look  somewhat  inwards,  as  is  seen  behind  and  at  the 
sides,  whilst  the  corresponding  teeth  of  the  upper  jaw  have  an  inclina- 
tion forw’ards  in  front  and  outwards  behind.  The  crowns  of  the  whole 
series  of  teeth  in  man  are  remarkably  even  in  height,  in  which,  how- 
ever, they  diminish  very  slightly  from  the  incisors  backwards  to  the 
wisdom  teeth.  In  consequence  of  the  large  proportionate  size  of  the 
upper  central  incisors,  the  other  teeth  of  the  upper  jaw  are  thrown 
somewhat  backwards,  so  that  in  closure  of  the  jaws  they  come  into 
contact  partly  with  their  corresponding  lower  teeth  and  partly  with 
the  lower  teeth  next  following.  Since,  however,  the  upper  dental  arch 
is  rather  larger,  and  the  crowns  of  the  molars,  especially  the  wisdom 
teeth,  above,  are  smaller  than  those  below,  the  dental  ranges  terminate 
behind  at  the  same  point  in  both  jaws. 

The  Milk  Teeth  (fig.  418). — The  forms  of  the  different  kinds  of  the 
temporary  teeth  resemble  those  of  the  permanent  set ; but  they  are  all 
smaller.  The  temporary  molar  teeth  {d,  c)  present  some  peculiarities. 
The  hinder  one  of  the  two  is  always  the  larger;  it  is  the  largest  of  all 
the  milk  teeth,  and  is  larger  even  than  the  second  permanent  bicuspid, 
by  which  it  is  afterwards  succeeded.  The  crown  of  the  first  upper 
milk  molar  has  only  three  cusps,  two  external  and  one  internal ; that 

VOL.  II.  35 


410 


SPECIAL  CHARACTERS  OF  THE  TEETH. 


of  tlie  second  has  four  distinct  cusps.  The  first  lower  temporary- 
molar  has  four  cusps,  and  the  second  five,  of  which  in  the  latter  case 
three  are  external.  The  fangs  of  the  temporary  molars  resemble 
those  of  the  permanent  set,  but  they  are  smaller,  and  are  more  diver- 
gent from  the  neck  of  the  tooth. 


[Fig.  418. 


Temporary  teeth,  a.  Central  incisor,  b.  Lateral  incisor,  c.  Canine,  d.  First  molar,  e.  Second 

molar. — W.] 


Structure- 


-On  making  a 


[Fig.  419. 


section  of  a tooth,  the  hard  substance  of 
which  it  is  composed  is  found  to  be  hollow 
in  the  centre  (fig.  419).  The  form  of  t.he 
cavity  bears  a general  resemblance  to 
that  of  the  tooth  itself ; it  occupies  the  in- 
terior of  the  crown,  is  widest  opposite  to 
the  neck,  and  extends  like  a fine  canal 
down  each  fang,  at  the  point  of  which  it 
opens  by  a small  orifice.  In  the  crown 
of  the  incisor  teeth  the  cavity  is  prolonged 
into  two  fine  linear  canals,  which  proceed 
one  to  each  corner  of  the  crown  ; in  the 
bicuspid  and  molar  teeth  it  advances  a 
short  distance  into  each  cusp.  In  the  case 
of  a root  formed  by  the  blending  of  twa 
or  more  fangs,  as  occurs  occasionally  in 
the  wisdom  teeth,  each  division  has  a se- 
parate canal  prolonged  down  to  its  apex. 
The  central  cavity  of  a tooth  is  called  the  pulp-cavity,  because  it 
is  occupied  and  accurately  filled  by  a soft,  highly  vascular,  and  sen- 
sitive substance,  called  the  denial  pulp.  This  pulp  consists  of  cellular 
filaments,  amongst  which  numerous  nuclei  are  rendered  visible  by  the 
action  of  acetic  acid.  It  is  well  supplied  with  vessels  and  nerves, 
which  are  derived  from  the  internal  maxillary  artery  and  the  filth 
pair,  and  which  enter  the  cavity  through  the  small  aperture  at  the 
point  of  each  fang:  according  to  Valentin  and  Hannover,  the  termina- 
tions of  the  nervous  fibres  are  looped. 

The  solid  portion  of  the  tooth  is  composed  of  three  distinct  sub- 
stances, viz.,  the  proper  dental  substance,  ivory  or  dentine,  (fig.  420,’) 


A view  of  an  incisor  and  of  a molar 
tooth,  in  longitudinal  section.  1.  The 
enamel.  2.  The  dentine.  3.  The  pulp- 
cavity. — S.  & H.] 


STRUCTURE  OF  THE  DENTINE. 


411 


the  enamel  (*),  and  the  cement  or  crusla  petrosa  (®).  The  dentine  con- 
stitutes by  far  the  larger  part  of  the  hard  substance  of  a tooth ; the 
enamel  is  found  only  upon  the  exposed  part  or  crown  ; and  the  cement 
covers  with  a thin  layer  the  surface  of  the  implanted  portion  or  fang. 

A.  The  ivory,  tooth  substance,  or  dentine,'^  (Owen,)  forming  the 
principal  mass  or  foundation  of  the  body  and  root  of  a tooth,  gives  to 
both  of  these  parts  their  general  form,  and  immediately  encloses  the 
central  cavity  (f).  It  resembles  very  compact  bone  in  its  general 
aspect  and  chemical  relations,  but  is  not  identical  with  it  in  structure, 
or  in  exact  proportions  of  its  earthy  and  animal  constituents. 

According  to  the  analyses  of  Berzelius  and  Bibra,  the  dentine  of 
human  teeth  consists  of  28  parts  of  animal,  and  72  of  earthy  matter. 
The  former  we  have  found  to  be  resolvable  into  gelatin  by  boiling,  as 
is  generally  believed,  although  Bibra  describes  it  as  similar  to  chon- 
drin,  mixed  with  a little  fat.  The  latter  is  composed  of  phosphate  of 
lime  with  traces  of  fluoride  of  calcium,  the  proportion  being,  accord- 
ing to  Bibra,  66-7  pr.  ct.,  carbonate  of  lime,  3’3,  phosphate  of  magne- 
sia and  other  salts,  T8.  Berzelius  found  5-3  parts  of  carbonate  of  lime. 

Though  appearing  to  the  naked  eye  to  have  a compact  structure, 
the  dentine,  when  examined  under  the  microscope,  is  seen  to  consist 

Fig.  421. 


Fig.  420.  After  Relzius.  — Magnified  re- 
presentation, or  rather  diagram,  of  a bicus- 
pid tooth  divided  longitudinally.  1.  The 
ivory  or  dentine,  showing  the  direction  and 
primary  curves  of  the  dental  lubuli.  2.  The 
pulp-cavity,  showing  the  orifices  of  the 
tubuli.  3.  The  crusta  petrosa  or  cement 
covering  the  fang  as  high  as  the  border  of 
the  enamel  at  the  neck.  The  stars  indicate 
that  it  contains  lacunte  like  those  of  bone. 
4.  The  enamel  resting  on  the  dentine. 

Fig.  421.  Section  of  the  dentine  made 
across  the  tubuli,  highly  magnified.  After 
Retzius.  1,  2,  3.  Dentinal  tubes  in  transverse 
section,  exhibiting  their  cavity  and  walls. 
4,  5,  6.  The  tubuli  obliquely  cut. 

of  an  immense  number  of  very  fine  tubes,  having  distinct  parietes, 
and  passing  very  close  to  each  other,  through  a hai'd  intermediate 
substance,  named  the  intertubular  tissue.  These  tubes,  called  dental 
tubuli,  were  long  since  discovered  and  described  by  Leeuwenhoek, 


Fig.  420. 


412 


STRUCTURE  OF  THE  DENTINE. 


but  his  observations  were  disregarded  until  the  tubular  structure  was 
again  brought  to  light  through  the  modern  researches  of  Purkinje  and 
Reizius,  by  whom,  and  by  others,  it  has  now  been  very  minutely  ex- 
amined and  described.  The  tubules  of  the  dentine  open  at  their  inner 
end  into  the  pulp-cavity,  appearing  as  minute  orifices  on  its  sides  (“). 
From  thence  they  pass  in  a radiated  manner  through  every  part  of  the 
ivory  towards  its  periphery.  In  the  upper  portion  of  the  crown  they 
have  a vertical  direction;  but  towards  the  sides,  and  in  the  neck  and 
root,  they  become  gradually  obli(]ue,  then  horizontal,  and  are  finally 
even  inclined  downwards  towards  the  point  of  the  fang.  The  course 
of  the  tubules  is  not  straight,  but  each  describes,  in  passing  from  the 
central  to  the  peripheral  part  of  the  dentine,  two  or  three  gentle 
curves  {‘primary  curvatures,  Owen),  and  is  besides  bent  throughout 
its  whole  length  into  numerous  fine  undulations,  which  follow  closely 
upon  one  another;  these  are  the  secowr/ary  curvatures.  In  adjacent 
tubules  both  kinds  of  curvatures  so  far  correspond  that  the  tubes 
themselves  are  nearly  parallel,  being  only  slightly  divergent  from  each 
other;  and  as  they  divide  several  times  dichotomously,  and  at  first 
without  being  much  diminished  in  size,  they  continue  to  occupy  t.he 
substance  of  the  dentine  with  nearly  equidistant  tubes,  and  thus  pro- 
duce,-when  seen  in  fine  seotions  of  the  tooth  made  parallel  to  their 
course,  a striated  appearance,  as  if  the  dentine  were  made  up  of  fine 
parallel  fibres.  The  concurrence  of  many  of  these  parallel  curvatures 
of  the  dental  tubuli  produces,  by  the  manner  in  which  they  reflect 
the  light,  an  appearance  of  concentric  lines  in  the  dentine,  see  fig. 
420,  which  may  be  well  seen  with  a low  magnifying  power.  The 
average  diameter  of  each  tubule  near  its  inner  and  larger  end  is 
of  an  inch,  and  the  distance  between  adjacent  tubules  is  about  two  or 
three  times  their  width.  (Retzius.)  From  their  sides  numerous  im- 
measurably fine  branches  are  given  off,  which  penetrate  the  hard  in- 
tertubular substance,  where  they  either  anastomose  or  terminate 
abruptly,  or,  according  to  some,  end  in  very  minute  cells.  These 
lateral  ramuscles  are  said  to  be  more  abundant  in  the  fang.  Near  ihe 
periphery  of  the  ivory  they  are  very  numerous,  and,  together  with  the 
main  tubules  themselves,  which  there,  by  rapid  division  and  subdivi- 
sion also  become  very  fine,  terminate  by  joining  together  in  loops,  or 
end  in  little  dilatations,  from  which  other  ramuli  are  given  oflT,  or  m 
minute  cells.  They  are  also  occasionally  seen  to  pass  on  into  the 
cement  which  covers  the  fang,  and  to  communicate  with  the  small 
ramified  canals  of  the  characteristic  lacunae  found  in  that  osseous 
layer.  The  minute  cells  belonging  to  the  intertubular  substance  of 
the  human  tooth  are  very  few  in  number  and  small,  and  hence  not. 
conspicuous,  but  they  are  larger  and  more  numerous  in  the  tooth  of 
the  horse.  They  are  most  distinct  in  the  outer  layer  of  the  dentine, 
which  is  immediately  beneath  the  enamel  or  cement,  and  is  named  the 
granular  layer  by  Purkinje.  The  surface  of  the  dentine  where  it  is  in 
contact  with  the  enamel  is  marked  by  undulating  grooves  and  ridges, 
and  also  by  numerous  minute  hexagonal  depressions,  to  which  the 
microscopic  fibres  of  the  enamel  are  accurately  adapted. 

The  dental  tubules,  when  highly  magnified,  appear  like  dark  lines 


STRUCTURE  OF  THE  ENAMEL. 


413 


against  transmitted  light,  but  are  white  when  seen  upon  a black 
ground.  This  is  owing  either  to  their  containing  an  opaque  granular 
calcareous  deposit,  as  some  suppose,  or  merely  to  a certain  degree  of 
opacity  of  their  parietes.  Their  tubular  character  is  proved  by  the 
fact  that  ink,  and  other  fluids,  together  with  minute  bubbles  of  air, 
have  been  seen  to  pass  along  them.  Their  walls  are  comparatively 
thick,  and  are  readily  distinguishable  from  the  intertubular  substance, 
as  may  be  seen  in  a transverse  section,  similar  to  that  figured  by 
Retzius,  fig.  421.  In  the  temporary,  and  sometimes  even  in  the 
permanent  teeth,  the  tubules  are  constricted  at  short  intervals,  so  as 
to  present  a moniliform  character.  (Nasmyth,  Owen,  Tomes.) 

The  intertubular  substance  is  translucent,  and  finely  granular 
(Tomes) ; it  contains  the  greater  part  of  the  earthy  substance  of  the 
dentine.  The  animal  basis  which  remains  after  this  has  been  removed 
by  an  acid,  is  described  by  Henle  as  separable  into  bundles  of  pale 
flattened  granular  fibres  running  in  a direction  parallel  with  the  tubes, 
and  by  Nasmyth  as  consisting  of  brick-shaped  cells,  built  up,  as  it 
were,  around  the  tubules,  which,  w'e  may  remark,  are  by  this  observer 
regarded  as  solid  fibres.  Neither  of  these  statements,  however,  is 
easily  reconcilable  with  what  we  have  observed  in  tbe  softened  teeth 
of  the  cachalot  or  sperm  whale ; for  in  these  the  animal  substance  can 
be  readily  torn  into  fine  lamella,  disposed  parallelly  with  the  internal 
surface  of  the  pulp-cavity,  and  therefore  across  the  direction  of  the 
tubules.  In  these  lamellae  the  sections  of  the  tubules  appear  as  round 
or  oval  apertures,  the  lamellae  having  the  same  relation  to  the  tubules 
as  those  of  true  bone  to  the  canaliculi. 

B.  The  enamel  (fig.  420,^)  is  that  hard  white  covering  which  en- 
crusts and  protects  the  exposed  portion  or  crown  of  a tooth.  It  is  the 
hardest  of  all  the  dental  tissues,  but.  it  becomes  worn  down  by  pro- 
tracted use.  It  is  thickest  on  the  grinding  surface  and  cutting  edges 
of  the  teeth,  and  becomes  gradually  thinner  towards  the  neck,  where 
it  ceases.  Its  extent  and  thickness  are  readily  seen  on  charring  the 
tooth,  by  which  the  dentine  becomes  blackened,  whilst  the  enamel, 
owing  to  the  very  small  quantity  of  animal  matter  in  its  composition, 
remains  white.  According  to  Bibra,  it  contains  of  earthy  constituents 
96-5  per  cent.,  viz.,  phosphate  of  lime  with  traces  of  fluoride  of  cal- 
cium 89‘8,  carbonate  of  lime  4*4,  phosphate  of  magnesia  and  other 
salts  T3;  and  has  only  3*5  per  cent,  of  animal -matter.  Berzelius, 
however,  gives  the  proportion  of  carbonate  of  lime  as  8,  and  of  ani- 
mal matter  as  only  2 per  cent. 

The  enamel  (fig.  42l,‘‘)  is  made  up  entirely  of  very  hard  and  dense 
microscopic  fibres  of  prisms,  composed  almost  wholly  of  earthy  matter, 
arranged  closely  together,  side  by  side,  and  set  by  one  extremity  upon 
the  subjacent  surface  (^)  of  the  dentine  {^).  On  the  summit  of  the 
coronal  portion  of  the  tooth,  these  enamel  fibres  are  directed  verti- 
cally, but  on  the  sides  they  are  nearly  horizontal.  As  seen  on  a sec- 
tion they  are  disposed  in  gently  waving  lines,  parallel  with  each  other, 
but  not  so  regular  as  the  curvatures  of  the  tubuli  of  the  dentine,  with 
which  they  have  no  agreement.  The  concurrence  of  these  parallel 
curvatures  produces,  as  in  the  case  of  the  dentine,  an  appearance  of 

35* 


414 


STRUCTURE  OF  THE  ENAMEL. 


concentric  lines  ('*)  in  the  enamel,  which  may  be  seen  with  a lens  of 
low  [)0\yer.  Minute  fissures  not  unfrequently  exist  in  the  deep  part  of 
the  enamel,  which  run  between  clusters  of  the  fibres  down  to  the  sur- 
face of  tlie  dentine ; and  other  much  larger  and  evident  fissures  are 
often  observed  leading  down  from  the  depressions  or  crevices  between 
the  cusps  of  the  molar  and  premolar  teeth.  The  surface  of  the  enamel, 
especially  in  the  milk  teeth,  is  marked  by  concentric  ridges,  which 
may  be  distinguished  with  a common  magnifying  glass,  and  which 
are  probably  occasioned  by  the  ridges  and  furrow's  already  described 
upon  the  coronal  portion  of  the  dentine. 

The  enamel  fibres  are  described  by  Retzius  as  being  solid  hexagonal 
prisms,  but  by  others  they  are  said  rather  to  be  four-sided.  Their 
diameter  varies  slightly,  and  is  ordinarily  about  of  an  inch.  They 
are  marked  at  small'  intervals  by  dark  transverse  lines,  (fig.  424.) 


Fig.  422.  Fig.  423. 


Fig.  422.  A vertical  section  of  an  imperfectly  developed  incisor,  taken  from  the  follicle  in 
which  it  was  enclosed ; this  section  is  meant  to  show  the  position  of  the  enamel  fibres,  and  also 
that  a part  of  the  appearances  which  are  seen  in  tliis  substance  under  a less  magnifying  power, 
originate  in  parallel  curvatures  of  the  fibres;  1.  1,  the  enamel;  2,  2,  the  dentine,  or  ivory; 
3,  3,  the  minute  indentations  and  points  on  the  surface  of  the  ivory,  on  which  the  enamel  fibres 
rest ; 4,  4,  parallel  erlamel  fibres;  5,  parallel  flexions  of  the  fibres  of  the  dentine  in  these  stripes. 

Fig.  423.  A portion  of  the  surface  of  the  enamel  on  which  the  hexagonal  terminations  of  the 
fibres  are  shown — highly  magnified  ; 1,  2,  3,  are  more  strongly  marked  dark  crooked  crevices, 
running  between  the  rows  of  the  hexagonal  fibres. 

Fig.  424.  The  fibres  of  the  enamel  viewed  sideways  under  a magnifying  power  of  350  times; 
1,  1,  the  enamel  fibres;  2,  2,  the  transverse  stripes  upon  them. — C.] 

According  to  Mr.  Tomes,  the  fibre  is  not  in  all  cases  solid,  but  has  an 
extremely  minute  cavity  in  part  or  whole  of  its  length,  which  is  be.st 
seen  in  newly  developed  enamel,  but  is  also  visible  in  adult  teeth. 
Their  inner  ends  are  implanted,  as  it  were,  into  the  minute  hexagonal 
depressions  found  on  the  surface  of  the  dentine,  whilst  the  outer  ends, 
somewhat  larger  in  diameter,  are  free,  and  present,  when  examined 
with  a high  magnifying  power,  a tessellated  appearance. 

On  submitting  the  enamel  to  the  action  of  dilute  acids,  it  is  almost 


STRUCTURE  OF  THE  ENAMEL. 


415 


entirely  dissolved,  and  leaves  scarcely  any  discernible  traces  of  animal 
matter.  Near  the  deep  surface  this  is  rather  more  abundant, Record- 
ing to  the  observations  of  Retzius,  who  conceived  that  it  there  aided 


Fig.  425  represents  a portion  oUenamel  from  a human  incisor  tooth  before  its  eruption.  The 
mass  to  the  left,  was  taken  from  the  exterior  part  of  the  enamel,  and  exhibits  the  transverse 
truncation  of  the  fibres  upon  the  free  surface  of  the  enamel,  and  the  oblique  truncation  at  the 
other  extremities. 

Fig.  426.  Hexagonal  prisms  of  enamel,  highly  magnified,  from  the  exterior  part  of  the  enamel 
of  an  embryo  incisor  tooth.  Circular  outlines  were  seen  upon  the  free,  transversely  truncated 
extremities,  which  I presumed  to  be  the  outline  of  the  nucleus. — From  nature,  by  J.  L.] 

in  fixing  the  enamel  fibres.  By  the  aid  of  an  acid,  the  enamel  of  newly 
formed  or  still  growing  teeth,  may  be  broken  up,  and  its  structural  ele- 
ments more  easily  distinguished.  The  prisms  are  then  found  to  have 
interposed  between  them  a delicate  membranous  structure  representing, 
in  fact,  the  walls  of  cells  which  have  coalesced  and  formed  moulds  for 
the  deposition  of  the  calcareous  matter.  As  this  latter  accumulates 
the  membranous  structure  becomes  almost  or  entirely  obliterated,  and 
the  now  earthy  prisms  are  inseparably  consolidated.  'Fhe  transverse 
strias  are  considered  by  Retzius  and  others  as  the  indication  of  the 
pre-existing  walls  of  coalesced  cells. 

[The  structure  of  the  enamel  may  be  best  studied  on  the  tooth  before  its  erup- 
tion ; at  this  period  the  enamel  fibres  or  prisms  are  readily  separated  from  one 
another  (fig.  425). 

The  fibres  present  the  appearance  of  transparent  and  pretty  regular  hexagonal 
prisms,  but  instead  of  being  terminated  at  the  extremities  by  a surface  at  right 
angles  to  the  length  of  the  fibres,  it  has  always  appeared  to  me  to  be  oblique, 
and  the  striae,  which  are  usually  represented  as  being  transverse,  appear  to  have 
the  same  course  as  the  obliquely  truncated  extremities  of  the  fibres.  These 
prisms  readily  break  up  into  very  minute  hexagonal  facets,  along  the  course  of 
the  oblique  strias. 

The  membrane  (fig.  429)  which  surrounds  the  enamel  fibres,  is.  also  marked 
with  oblique  striae  corresponding  to  those  of  the  fibres. 

The  fibres  originate  in  nucleolo-nucleated  cells  (fig.  430),  w'hich,  at  first  spheri- 
cal, become  elongated  and  take  upon  themselves  the  form  of  the  future  enamel 
fibres  (fig.  427). 

After  the  calcification  of  the  interior  of  the  enamel  cells,  which  appears  to  have 
a regular  disposition  of  thin  laminas,  giving  rise  to  the  oblique  striae  of  the  enamel 
fibres,  the  ceU-wall  for  a time  is  readily  separable,  but  finally  becomes  obliterated. 

The  enamel  fibres,  forming  the  exterior  part  of  the  enamel,  upon  the  free  sur- 
face of  the  latter,  are  transversely  terminated  (fig.  426). — J.  L.] 

The  third  substance  which  enters  into  the  formation  of  the  teeth  is 
the  crusta  petrosa  or  cement  (fig.  420,®).  This  is  a layer  of  true  bone. 


[Fig.  425, 


Fig.  426. 


416 


STRUCTURE  OF  THE  CEMENT. 


slightly  modified  in  structure,  which  invests  that  part  of  the  dentine 
which  is  not  protected  by  the  enamel.  It  covers  the  whole  fang, 


[Fig.  427.  Fig.  428.  Fig.  429. 


Fig.  427.  Enamel  cells  from  an  embryo  canine  tooth,  highly  magnified,  the  contents  calcified 
but  still  in  a very  friable  condition.  The  nucleoli  were  visible. 

Fig.  428.  Several  enamel  fibres,  from  an  embryo  molar,  highly  magnified  and  exhibiting  the 
obliquely  truncated  extremities.  In  one  the  oblique  strise  are  represented,  in  the  course  of  which 
the  fibres  have  a great  disposition  to  fracture. 

Fig.  429.  A portion  of  membrane  which  surrounds  the  enamel  fibres,  highly  magnified,  from 
an  embryo  incisor.  It  exhibits  the  oblique  striae,  corresponding  to  those  of  the  enamel  fibres. 

Fig.  430.  Transverse  section  of  enamel  cells,  calcified,  highly  magnified,  from  an  embryo  in- 
cisor, exhibiting  the  cell-wall  (1),  the  nuclei  (2),  and  the  niieleoli  (3). — From  nature,  by  J.  L.] 

towards  the  lower  end  of  which  it  becomes  gradually  thicker,  and  is 
especially  developed  at  the  apex,  and  along-the  grooves  of  the  com- 
pound fangs.  Besides  this  it  has  been  traced  by  Purkinje,  Nasmyth, 
and  Owen,  as  a very  thin  layer,  which,  however,  soon  gets  worn  off’, 
over  the  enamel  upon  the  crown  ; and  in  the  compound  teeth  of  many 
herbivorous  animals,  the  existence  of  this  coronal  cement  is  evident 
enough.  As  life  advances  the  cement  is  generally  found  to  become 
thicker,  especially  near  the  apex  of  the  fang,  where  it  sometimes 
blocks  up  the  orifice  leading  into  the  pulp-cavity. 

The  crusta  petrosa  contains  cells  and  canaliculi  resembling  those  of 
bone;  they  are  placed  lengthwise  around  the  fang,  and  give  off  minute 
radiated  ramifications,  which  are  often  found  to  proceed  from  one 
side  only  of  a cell,  towards  the  'periodontal  surface  (Tomes).  These 
cells  have  not  been  seen  in  the  coronal  cement  of  human  teeth,  but 
only  in  that  of  the  implanted  portion  : in  the  deep  layers  of  the  cement, 
the  fine  canaliculi  sometimes  anastomose  with  some  of  the  terminal 
tubules  of  the  subjacent  dentine.  Where  the  cement  is  very  thick,  it 
may  contain  vascular  canals,  analogous  to  the  Haversian  canals  of 
bone.  On  the  deciduous  teeth  the  cement  is  thinner  and  contains 
fewer  cells.  In  chemical  composition  it  resembles  bone  and  contains 
30  per  cent  of  animal  matter.  The  cement  is,  according  to  some, 
extremely  sensitive  at  the  neck  of  ihe  tooth,  if  it  be  exposed  by  retrac- 
tion of  the  gum.  By  its  connexion  with  the  surrounding  membranous 


DEVELOPMENT  OF  THE  TEETH. 


417 


structures  it  contributes  to  fix  the  tooth  in  the  socket.  It  is  the  seat 
of  the  bony  growths  or  exostoses  sometimes  found  upon  the  teeth. 

It  has  been  long  observed  that,  after  the  age  of  twenty  years  or 
later,  the  central  cavity  of  a tooth  becomes  gradually  diminished  in 
size,  by  the  deposit  of  a hard  substance  on  the  inner  surface  of  the  den- 
tine, whilst  the  pulp  slowly  shrinks  or  disappears.  This  additional  sub- 
stance, once  considered  to  be  an  extension  of  the  cement  into  the  inte- 
rior of  the  tooth,  has  been  shown  to  have  a distinct  structure,  in  part 
resembling  dentine,  and  in  part  bone.  It  is  the  horvy  substance  of 
Blumenbach,  and  is  named  osteodentine  (Owen),  and  secondary  dentine 
(Tomes).  It  is  traversed  by  canals,  which  contain  blood-vessels,  and 
are  surrounded  by  concentric  lamellae,  like  the  Haversian  canals  of 
bone.  From  these  canals,  numerous  tubules  radiate  in  all  directions, 
but  have  no  calcigerous  cells  connected  with  them  : moreover,  the 
tubules  are  larger  than  those  of  bone,  resembling,  in  this  respect,  and 
also  in  their  mode  of  ramification,  the  tubes  of  the  dentine.  This 
newly  added  structure  may  or  may  not  coalesce  with  the  previously 
formed  dentine;  it  appears  to  be  produced  by  a slow  conversion  of 
the  dental  pulp. 

DEVELOPMENT  OF  THE  TEETH. 

The  development  of  the  teeth  includes  a description  of  their  origin 
and  growth,  as  distinct  organs, — of  their  order  of  eruption  in  two  sets, 
— and  also  an  account  of  the  formation  of  their  component  tissues,  the 
dentine,  enamel,  and  cement. 

The  recent  observations  of  Arnold  and  Goodsir,  made  independently 
of  each  other,  have  given  precision  to  our  knowledge  concerning  the 
origin  and  mode  of  growth  of  the  teeth,  and  have  fully  established  the 
fact,  that  the  teeth  are  developed  from  the  mucous  membrane  covering 
the  edges  of  the  maxillary  arches.  The  changes  which  take  place  in 
the  bones  of  the  jaws  relate  only  to  the  formation  of  the  sockets  for 
the  teeth.  In  the  earliest  condition  these  bones  present  no  appearance 
of  alveoli,  but,  concurrently  with  certain  changes  in  the  mucous  mem- 
brane, to  be  immediately  described,  a wide  groove  is  developed  along 
the  edge  of  the  jaw,  w'hich  gradually  becomes  deeper,  and  is  at  length 
divided  across  by  thin  bony  partitions,  so  as  to  form  a series  of  four- 
sided cells.  These  bony  septa  are  not  distinctly  formed  until  nearly 
the  fifth  month  of  foetal  life.  By  the  subsequent  growth  of  the  bone, 
these  cavities  or  loculi  are  gradually  closed  round,  but  always  continue 
open  at  the  edge  of  the  jaw.  By  the  end  of  the  sixth  month  they  are 
distinctly  formed,  but  continue  afterwards,  (see  figs.  63,  c,  and  74, 
pp.  142  and  150,)  in  proportion  to  the  growth  of  the  teeth,  to  increase 
in  size  and  depth,  by  the  addition  of  new  matter,  which  widens  and 
deepens  the  jaw. 

The  first  stages  in  the  development  of  the  teeth,  as  observed  by  Ar- 
nold and  Goodsir,  consist  of  certain  changes  in  the  mucoQs  membrane 
covering  the  borders  of  the  maxillae.  (Consult  fig.  431,  and  its  de- 
scription.) About  the  sixth  week  of  embryonic  life,  a depression  or 
groove,  having  the  form  of  a horseshoe,  appears  along  the  edge  of 
the  jaw,  in  the  mucous  membrane  of  the  gum;  that  is  xhe  primitive 
dental  groove  (Goodsir).  From  the  floor  of  this  groove  (supposed  to 


418 


DEVELOPMENT  OF  THE  TEETH. 


be  represented  in  a transverse  section,  in  fig.  431,  1)  a series  of  ten 
papillas,  as  at  2,  arise  in  succession  in  each  jaw,  and  constitute  the 
germs  or  rudimentary  pulps  of  the  milk  teeth.  The  order  in  which 

[Fig.  431. 


From  Goodsir. — A series  of  diagrams,  representing  imaginary  seclionf  made  across  the  edge  of 
the  lower  jaw  of  the  fetus  at  different  periods,  in  order  to  show  the  successive  stages  in  the 
development  of  the  sac  of  a temporary  incisor  tooth,  and  of  the  succeeding  permanent  tooth, 
from  the  mucous  membrane  of  the  jaw. — 1.  The  dental  groove  is  formed  in  the  mucous  mem- 
brane.  2.  The  groove  widens,  and  has  a papilla  at  the  bottom:  this  is  the  papillary  stage.  3,  4, 
and  5 represent  the  follicular  stage  ; the  lips  of  the  groove  enlarge,  and  form  a sunken  follicle, 
in  which  the  papilla,  now  enlarged  and  beginning  to  acquire  the  form  of  the  future  tooth-pulp, 
is  hid.  Membranous  opercula,  or  laminae,  are  formed  from  the  sides  of  the  follicle,  and,  as  seen 
in  5,  meet  over,  leaving  a Innated  depression  behind.  The  diagram,  5,  supposing  the  opercula 
to  be  gently  opened  out,  may  be  taken  to  represent  a cross  section  through  an  incisor  follicle,  as 
indicated  by  the  dotted  line  a h,  fig.  436.  6.  'I'he  lips  of  the  groove  also  meet,  except  the  lunatcd 
depression,  c.  7.  The  opercula  and  lips  of  the  groove  cohere;  the  follicle  becomes  a closed  sac 
(s);  the  papilla  is  the  tooth-pulp  (/)),  and  has  the  shape  of  the  crown  of  the  future  tooth  ; and  the 
lunated  depression  becomes  a cavity  of  reserve  (c)  for  the  development  of  the  succedancous  per- 
manent tooth  : the  saccular  stage  is  now  complete.  The  remaining  figures.  8 to  12,  show  the 
commencement  of  the  cap  of  dentine  on  the  pulp,  the  subsequent  steps  in  the  formation  of '.he 
milk  tooth,  and  its  eruption  through  the  gum  (11);  also  the  gradual  changes  in  the  cavity  of 
reserve,  the  appearance  of  it.s  laminaj  and  papilla,  its  closure  to  form  the  sac  of  the  permanent 
tooth,  its  descent  into  the  jaw,  behind  and  below  the  milk-tooth,  and  the  long  pedicle  (12)  formed 
by  its  upper  obliterated  portion. 

these  papillae  appear  is  very  regular.  The  earliest  is  that  for  the  first 
milk  molar  tooth ; it  is  seen  at  the  seventh  week,  as  soon  as  the  dental 
groove  is  formed ; at  the  eighth  week  that  for  the  canine  tooth  ap- 
pears ; the  two  incisor  papillae  follow  next,  at  about  the  ninth  week, 
the  central  one  before  the  lateral ; lastly,  the  second  molar  papilla  is 
visible  at  the  tenth  week,  at  which  period  this,  the  papillary  stage  (2) 
of  the  rudiments  of  the  teeth  is  completed.  The  papillae  in  the  upper 
jaw  appear  a little  earlier  than  those  in  the  lower  jaw. — In  the  next 
place,  the  margins  of  the  dental  groove  become  thickened  and  promi- 
nent, especially  the  inner  one  ; and  membranous  septa  pass  across 
between  the  papillae  from  one  margin  to  the  other,  so  as  to  convert 
the  bottom  of  the  groove  into  a series  of  follicles,  each  containing  one 
of  the  papillae.  These  changes  constitute  \he  follicular  stage  (3) ; they 
take  place  in  the  same  order  as  that  in  which  the  papillae  appeareii, 
and  are  completed  about  the  fourteenth  week  (fig.  431,  4,  and  fig.  432), 
During  the  early  part  of  this  period  the  papillae  grow  rapidly,  they 
begin  to  show  peculiarities  of  form,  and  project  from  the  mouths  of 
the  follicles.  Soon,  however,  the  follicles  become  deeper,  so  as  to 
hide  the  papillae  (fig.  432),  which  now  assume  a shape  corresponding 
with  that  of  the  crowns  of  the  future  teeth.  Small  laminae,  or  opercula 


DEVELOPMENT  OF  THE  TEETH. 


419 


Fig.  432. 


An  enlarged  view  of  the  upper  jaw 
and  palate  of  a fetus  at  about  I he  four- 
teenth week,  showing  the  follicular 
stage  of  the  development  of  the  milk 
teeth.  The  ten  follicles,  each  contain- 
ing a papilla,  are  distinctly  seen. 


of  membrane  (fig.  431,  4 and  5),  are  then 
developed  from  the  sides  of  each  follicle, 
their  number  and  position  being  regulated, 
it  is  said,  by  the  form  of  the  cutting  edges 
and  tubercles  of  the  intended  teeth : the 
incisor  follicles  (fig.  436,^,*)  having  two 
laminee  (o),  one  external  and  one  internal ; 
the  canine  (®),  three,  of  which  two  are 
internal,  and  the  molars  (‘,  ®)  four  or  five 
each. — The  lips  of  the  dental  groove,  as 
well  as  the  opercula,  now’  begin  (fig.  431, 

6)  to  cohere  over  the  follicles  from  behind 
forwards,  the  posterior  lip  being  very 
much  thickened  ; the  groove  itself  is  thus 
gradually  obliterated  (7),  the  follicles  are 
converted  into  closed  sacs  (s),  and  the 
saccular  stage  of  the  milk  teeth  is  thus 
completed  about  the  end  of  the  fifteenth 
week.  Certain  lunated  depressions  (5, 

6,  c,  also  fig.  436,  c),  which  are  formed  one  behind  each  of  the  milk 
follicles  about  the  fourteenth  week,  escape  the  general  adhesion  of  the 
lips  of  the  groove.  From  these  depressions,  as  will  be  afterwards  de- 
scribed, the  sacs  of  the  ten  anterior  permanent  teeth  are  subsequently 
developed. 

The  dental  sacs  (fig.  431,  7 s),  thus  formed  by  the  closure  of  the 
follicles,  continue  to  enlarge,  as  well  as  their  contained  papillse  (p). 
The  walls  of  the  sacs,  which  soon  begin  to  thicken,  consist  of  an  outer 
fibro-cellular  membrane,  and  an  internal  highly  vascular  layer,  lined 
by  epithelium ; their  blood-vessels  are  derived  partly  from  the  dental 
arteries  w’hich  course  along  the  base  of  the  sacs,  and  partly  from  those 
of  the  gums. 

The  papillae,  now  the  dental  pulps,  adhere  by  a wide  base  to  the 
bottom  of  the  sacs,  and,  having  acquired  a perfect  resemblance  to  the 
crowns  of  the  future  teeth,  the  formation  of  the  hard  substance  com- 
mences in  them.  This  process  begins  very  early,  and  by  the  end  of 
the  fourth  month  of  fetal  life,  thin  shells  or  caps  of  dentine  are  found 
on  all  the  pulps  of  the  milk  teeth,  and  a little  later  on  that  of  the  first 
permanent  molar.  The  mode  in  which  it  proceeds,  taking  a canine 
tooth  as  an  example,  may  be  stated  as  follows : a thin  osseous  shell  or 
cap  of  dentine  appears  on  the  point  of  the  pulp;  this  increases  in 
extent  by  a growth  around  its  edges,  and  in  thickness  by  a similar 
formation  in  its  interior,  the  latter  taking  place  at  the  expense  of  the 
substance  of  the  pulp  itself,  which  accordingly  decreases  in  proportion. 
This  growth  of  the  tooth  continues  until  the  crown  is  completed  of  its 
proper  width, and  then  the  pulp  undergoes  a constriction  at  its  base  to 
form  the  cervix  of  the  tooth.  From  that  time  the  pulp  elongates  and 
continues  to  become  narrower,  so  as  to  construct  the  fang  (10,  11). 
During  the  whole  period,  another  process  has  been  going  on,  by  which 
the  outer  surface  of  the  crown  is  covered  with  the  enamel.  This 
substance  is  formed  from  a thickened  portion  of  the  parietes  of  the 


420 


DEVELOPMENT  OF  THE  TEETH. 


sac,  which  is  accurately  adapted  to  the  surface  of  the  dental  pulp,  or 
to  its  cap  of  dentine,  and  was  called  by  Hunter  the  outer  pulp. 
Sooner  or  later,  after  the  completion  of  the  crown,  this  part  of  the 
tooth  appears  through  the  gum  (11),  whilst  the  growth  of  dentine  to 
complete  the  fang  is  continued  at  the  surface  of  the  elongating  pulp, 
which  gradually  becomes  encroached  upon  by  successive  formations 
of  hard  substance,  until  only  a small  cavity  is  left  in  the  centre  of  the 
tooth,  containing  nothing  but  the  reduced  pulp,  supplied  by  a slender 
thread  of  vessels  and  nerves,  which  enter  by  a little  aperture  left  at 
the  point  of  the  fang  after  the  dentine  is  completed.  In  the  case  of 
teeth,  having  complex  crowns  and  more  than  a single  fang,  the  pro- 
cess is  somewhat  modified.  On  the  surface  of  the  dental  pulp  of  such 
a tooth,  as  many  separate  little  shells  of  dental  substance  are  formed 
as  there  are  eminences  or  points  (fig.  433,^);  these  soon  coalesce •(“), 
and  the  formation  of  the  tooth  proceeds  as  before  as  far  as  the  cervix. 
The  pulp  then  becomes  divided  into  two  or  more  portions,  corre- 
sponding with  the  future  fangs,  and  the  ossification  advances  in  each 
as  it  does  in  a single  fang.  A horizontal  projection  or  bridge  of  den- 
tine (3,  4)  shoots  across  the  base  of  the  pulp,  between  the  commencing 
fangs,  so  that  if  the  tooth  be  removed  at  this  stage  and  examined  on 
its  under  surface,  its  shell  presents  as  many  apertures  as  there  are 
separate  fangs.  In  all  teeth,  the  pulp  originally  adheres  by  its  entire 


Fig.  433. 


Shows  the  mode  of  formation  of  a molar  tooth  with  two  fangs.  (Blake.) — 1.  Distinct  caps  of 
dentine,  which  afterwards  unite.  2,  3.  A bridge  of  dentine  is  beginning  to  stretch  across  the 
base  of  the  tooth-pulp,  artd  is  completed  in  4.  Henceforth  the  pulp  is  double,  and  each  part 
forms  its  own  fang. 

base  to  the  bottom  of  the  sac,  but  when  more  than  one  fang  is  to  be 
developed,  the  pulp  is,  as  it  were,  separated  from  the  sac  in  certain 
parts,  so  that  it  comes  to  adhere  at  two  or  three  insulated  points  only, 
whilst  the  dentine  continues  to  be  formed  along  the  intermediate  and 
surrounding  free  surface  of  the  pulp. 

Formation  of  the  hard  tissues  of  the  teeth. — a.  The  Dentine. — it 
was  at  one  time  supposed  that  this  substance  was  formed  by  a process 
of  ossification  similar  to  what  takes  place  in  the  cartilages  of  true 
bones;  but  this  opinion  subsequently  gave  way  to  another,  which 
prevailed  until  lately,  and  attributed  the  formation  of  the  tooth  to  a 
process  of  secretion  from  the  surface  of  the  pulp.  The  older  notion 
has  since  been  revived  by  Schwann,  in  applying  his  doctrine  of  the 
development  of  tissues  from  cells,  to  the  observations  previously  made 
by  Purkinje  and  Raschkow.  By  these  last-named  inquirers,  the  den- 
tine was  described  as  being  formed  in  continuous  layers  from  without 
inwards,  the  pulp  supplying  the  material : Schwann  expressed  his 


DEVELOPMENT  OF  THE  TEETH. 


421 


opinion,  that  it  was  in  reality  the  ossified  pulp.  This  doctrine  has 
received  general  support  from  subsequent  observers,  and  it  may  be 
regarded  as  established;  but  the  precise  changes  which  accompany 
the  conversion  of  the  pulp  into  dentine,  are  not  yet  - satisfactorily 
determined. 

Previously  to  the  commencement  of  ossification,  the  primitive  pulp 
is  found  to  consist  of  microscopic  nucleated  cells  (pulp-granules, 
Purkinje),  more  or  less  rounded  in  form,  and  embedded  in  a clear 
matrix  containing  a few  very  fine  molecules,  thinly  disseminated  in  it. 
It  contains  no  cellular  fibres,  but  is  highly  vascular.  The  capillary 
vessels  are  most  abundant  at  the  points  where  ossification  is  to  com- 
mence, but  do  not  reach  the  surface.  At  the  exterior  of  the  pulp,  the 
rounded  cells  become  elongated,  and  arranged  perpendicularly  to  the 
surface,  so  as  to  form  a tolerably  regular  layer,  resembling  a columnar 
epithelium.  Besides  this,  the  entire  pulp  is  covered  by  a fine  pellucid 
homogeneous  membrane,  named  the  preformative  membrane  (Purkinjd, 
Raschkow). 

In  the  process  of  ossification,  as  described  by  Schwann,  the 
elongated  cells,  at  the  surface  of  the  pulp,  together  with  the  inter- 
cellular matrix,  become  gradually  solidified  by  impregnation  with 
earthy  matter,  and  are  thus  converted  into  dentine.  Similar  changes 
of  elongation,  apposition,  and  solidification  by  earthy  deposit,  occur  in 
successive  layers  of  cells,  which  go  on  being  developed  in  the  pulp. 
The  preformative  membrane  is  either  obliterated,  or  according  to 
Purkinje,  Retzius,  and  Raschkow,  is  the  part  first  to  undergo  ossifica- 
tion, which  then  proceeds  to  affect  the  tissue  of  the  pulp  immediately 
beneath  it.  The  granular  layer  (Purkinje)  found  upon  the  surface  of 
the  dentine  next  to  the  enamel,  and  in  which  the  microscopic  cells  are 
chiefly  found,  is  conjectured  to  result  from  the  ossification  of  this 
membrane;  and  the  enamel  fibres  are  supposed  to  be  implanted  in  the 
minute  hexagonal  depressions  formed  on  its  outer  surface.  This  pre- 
formative membrane  was  noticed  by  Mr.  T.  Bell,  who  thought,  how- 
ever, in  accordance  with  the  views  then  generally  entertained,  that 
the  dentine  was  deposited  on  its  outer  surface.  On  gently  separating 
the  newly  formed  cap  of  dentine  from  the  formative  pulp,  in  the 
growing  teeth  of  the  human  subject  or  of  animals,  and  examining  it 
under  the  microscope,  the  elongated  cells  of  the  pulp  are  found  ad- 
hering in  numbers  to  the  inner  surface  of  the  newly  formed  dentine. 
The  hard  substance  undoubtedly  Increases  at  the  expense  of  the  pulp, 
and  difierent  observers  have  described  the  mode  in  which  the  pulp- 
cells,  their  nuclei  and  the  intercellular  matrix,  are  converted  into  the 
tubuli  and  intertubular  substance  of  the  dentine;  but  from  our  own 
observations  w’e  have  not  been  able  to  confirm  these  descriptions,  and 
we  are  disposed  to  regard  the  precise  nature  of  the  conversion  of  the 
soft  tissue  into  the  dentine  as  still  a matter  for  investigation. 

Schwann  at  first  conceived  that  the  tubuli  were  prolongations  of  the  cells,  and 
that  the  intertubular  substance  was  formed  by  the  calcification  of  the  matrix,  but 
he  abandoned  this  idea  after  comparative  researches  in  animals.  Henle  thought 
that  the  cells,  in  becoming  impregnated  with  earthy  matter,  formed  the  bundles 
of  fibres  of  which  the  dentine  is  supposed  by  him  to  consist;  whilst  the  nuclei 
became  elongated  into  the  hollow  tubes.  Owen  believes  that  the  nuclei  of  the 

VOL.  II.  36 


422 


FORMATION  OF  THE  ENAMEL. 


elongated  cells,  having  themselves  become  lengthened,  divide  both  longitudi- 
nally and  transversely  to  develope  secondary  cells  which  continue  included  within 
the  primary  cells.*  These  secondary  cells  then  elongate  and  together  with  their 
nuclei  join  end  to  end.  Calcification  proceeds  in  all  parts,  except  in  the  nuclei 
of  the  secondary  cells  which  remain  as  the  cavities  or  lumina  of  the  tubes;  the 
walls  of  the  secondary  cells  are  supposed  to  form  the  parietes  of  the  tubes,  and 
the  material  between  the  secondary  cells  together  wfith  the  walls  of  the  primary 
cells  to  be  converted  into  the  intertubular  substance.  The  bifurcation  of  the 
tubuli  is  said  to  result  from  the  junction  of  two  secondary  cells  with  a single  one 
in  a deeper  layer  of  the  pulp ; and  the  constricted  or  moniliforin  appearance  of 
the  tubuli  already  mentioned  as  having  been  seen  by  some  observers  in  growing 
or  even  in  mature  teeth,  is  thought  to  depend  on  an  imperfect  coalescence  of  the 
nuclei.  In  the  teeth  of  young  animals,  Mr.  Tomes  states  that  he  has  noticed  the 
division  of  the  cells  and  their  subsequent  coalescence  to  form  the  tubes,  but  he 
has  failed  to  recognise  the  existence  of  primary  cells  including  secondary  ones. 
We  must  confess,  that,  after  a careful  examination  of  the  human  teeth,  W'e  have 
been  unable  to  discover  any  of  the  above  described  changes,  except  the  enlarge- 
ment of  the  more  superficial  cells  of  the  pulp  and  their  elongation  in  the  imme- 
diate vicinity  of  the  dentine. 

b.  The  Enamel. — This  substance  is  formed  by  a peculiar  organ 
developed  in  the  outer  wall  of  the  sac,  at  the  same  time  that  the  den- 
tine is  being  produced  by  the  piilp.  Its  formation  commences  very 
early.  The  membranous  wall  of  the  sac,  soon  after  its  opercula  have 
united  together,  becomes  thickened  and  pulpy,  and  at  length  applies 
itself  in  the  form  of  a soft  mass  accurately  adapted  to  the  surface  of 
the  primitive  dental  pulp,  or  at  a later  period  to  the  cap  of  dentine. 
This  thickened  part  of  the  sac  is  the  outer  pulp  of  Hunter,  which,  as 
he  stated,  is  the  formative  organ  of  the  enamel  {organon  adamantince. 
Purkinje).  The  structure  of  this  enamel  pulp  is  very  remarkable:  it 
is  described  by  Todd  and  Bowman  as  consisting  of  an  open  web  of 
distinct  fibres,  holding  within  their  reticulations  a clear  fluid,  and 
having  a bright  spot' at  their  place  of  junction.  The  safne  structure 
was  previously  described  by  Purkinje  and  Raschkow,  as  formed  by 
radiating  cells,  like  the  actinenchyma  of  vegetable  tissues.  The  sur- 
face of  this  structure,  turned  towards  the  inside  of  the  dental  sac,  is 
covered  with  a fine  transparent  simple  membrane,  upon  which  rests  a 
thick  stratum  of  nucleated  cells,  which  compose  the  enamel  membrane 
(membrana  adamantince,  Purkinje),  a structure  analogous  to  epithe- 
lium. From  the  vascular  part  of  the  enamel  pulp,  villous  processes, 
containing  blood-vessels,  project  into  the  enamel  membrane,  at  Ine 
part  corresponding  with  the  grinding  surface  of  the  tooth.  At  first, 

[*  In  sections  of  dentine,  in  most  instances,  and  especially  towards  its  outer  periphery, 
numerous  curved  lines  (fig.  4.34, ''),  are  observed,  which  Mr.  Owen  regards  as  the  original 
contour  of  the  primary  dentinal  cells. 


Fig.  434. 


Section  of  the  crown  of  a human  molar  tooth,  highly  magnified.  1.  Dentine.  2.  Enamel. 
Periphery  of  the  dentine  or  base  upon  which  the  enamel  fibres  are  placed.  4.  Curved  ouliines 
indicating  the  original  contour  of  the  primary  dentinal  cells. — J.  L.] 


FORMATION  OF  THE  CEMENT. 


423 


the  layer  of  cells  composing  the  enamel  membrane  is  in  contact  with 
the  dental  pulp.  When,  however,  the  shell  of  dentine  begins  to  be 
formed,  a succession  of  those  nucleated  cells,  uniting  in  rows,  arrange 
themselves  vertically  to  its  surface,  become  elongated  and  prismatic, 
and  being  impregnated  with  earthy  matter,  form  the  solid  prismatic 
fibres  of  the  enamel,  which  coalesce  firmly  together.  Whilst  the 
enamel  is  being  formed,  it  is  soft  and  chalky,  and  can  easily  be  sepa- 
rated into  its  component  cells.  Afterwards  the  membranous  portion 
of  it  is  nearly  all  obliterated,  and  the  nuclei  entirely  disappear,  or 
according  to  Tomes,  elongate  into  a very  fine  central  canal  in  each 
fibre.  No  enamel  is  formed  except  on  the  crown  of  the  tooth;  either 
because  the  enamel  pulp  adheres  to  the  cervix,  or  because  the  cha- 
racter of  the  membrane  of  the  sac  changes  at  that  point. 

c.  The  Cement. — This  osseous  layer  appears  to  be  formed,  simul- 
taneously with  the  dentine  of  the  fang,  by  the  periodontal  membrane, 
from  the  margin  of  the  enamel  downwards.  As  to  the  origin  of  the 
coronal  cement,  it  is  supposed  by  sonTe  that  the  enamel  membrane 
itself,  after  its  proper  function  has  ceased,  is  converted  into  that  sub- 
stance, and  by  others  that  it  pours  out  a material  which  subsequently 
becomes  ossified. 

Eruption  of  the  temporary  teeth. — At  the  time  of  birth  (fig.  435)  the 
crowns  of  the  anterior  milk  teeth,  still  enclosed  in  their  sacs,  are  com- 
pleted within  the  jaw,  and  their  fangs  begin  to  be  formed.  Their 
appearance  through  the  gums  follows  a regular  order,  but  the  period 
at  which  each  pair  of  teeth  is  cut  varies  within  certain  limits.  The 


Fig.  435. 


CL,  Left,  and  6,  right,  half  of  the  lower  jaw  of  a child  at  birth,  with  part  of  the  bone  taken 
away  To  show  the  looth-sacs  as  they  lie  underneath  the  gnm.  The  lower  figure  shows  the  sacs 
of  the  milk-teeth  and  first  permanent  molar,  exposed  by  removing  the  bone  from  the  outside  ; the 
upper  figure  shows  the  same  from  the  inside,  with  the  sacs  ofthe  permanent  incisors  and  canine 
lying  behind  those  of  the  corresponding  milk  teeth. 

eruption  commences  at  the  age  of  seven  months,  and  is  completed 
about  the  end  ofthe  second  year.  It  begins  with  the  central  incisors 
of  the  lower  jaw,  which  are  immediately  followed  by  those  of  the 
upper  jaw;  and,  as  a general  rule,  each  of  the  lower  range  of  teeth 
rises  through  the  gum  before  the  corresponding  tooth  of  the  upper  set. 


424 


DEVELOPMliNT  OF  THE  PERMANENT  TEETH. 


The  following  scheme  indicates  in  months,  the  order  and  time  of  erup- 
tion of  the  milk  teeth. 


MOLARS. 

CANINES. 

INCISORS. 

CANINES. 

MOLARS. 

24—12 

18 

9 7 7 9 

18 

12—24 

Before  the  teeth  protrude  through  the  gum,  this  undergoes  some 
peculiar  changes : its  edge  at  first  becomes  dense  and  sharp,  but 
as  the  looth  approaches  it,  the  sharp  edge  disappears,  the  gum  be- 
comes rounded  or  tumid,  and  is  of  a purplish  hue;  the  summit  of  the 
tooth  is  seen  like  a white  spot  or  line  through  the  vascular  gum,  and 
soon  after  rises  through  it.  As  the  crown  of  the  tOoth  advances  to  its 
ultimate  position,  the  elongated  fang  becomes  surrounded  by  a bony 
socket  or  alveolus.  Before  the  eruption,  the  mucous  membrane  is 
studded  with  a number  of  small  white  bodies,  wbicb  were  described 
by  Serres,  as  glands  {dental  glands),  and  were  supposed  by  him  to 
secrete  the  tartar  of  the  teeth.  Meckel  thought  they  were  small 
abscesses,  because  no  aperture  could  be  detected  in  them.  As  exa- 
mined in  a foetus  of  six  months,  we  have  found  them  to  be  little  .round 
pearl-like  bodies  situated  in  the  chorioirof  the  mucous  membrane,  and 
having  no  aperture.  They  are  small  spherical  capsules  of  various 
sizes,  lined  w’ith  a thick  stratum  of  epithelium,  the  inner  cells  of  which 
are  flattened  or  scaly,  like  those  lining  the  cheek,  and  are  so  numerous 
as  almost  to  fill  up  the  cavity. 

Development  of  the  permanent  teeth. — The  preceding  description  of 
the  structure  of  the  dental  sacs  and  pulps,  and  of  the  mode  of  forma- 
tion of  the  several  parts  of  a tooth,  applies  to  the  permanent,  as  well 
as  to  the  milk  teeth. 

The  origin  and  progressive  development  of  the  sacs  of  the  perma- 
nent teeth,  have  still  to  be  considered.  There  are  six  more  permanent 
teeth  in  each  jaw  than  there  are  milk  teeth,  and  it  is  found  that  the 
sacs  of  the  ten  anterior  permanent  teeth,  which  succeed  the  ten  milk 
teeth,  have  a different  mode  of  origin  from  the  six  additional  or  super- 
added  teeth,  which  are  formed  further  back  in  tbe  jaw. 

The  sacs  and  the  pulps  of  the  ten  anterior  permanent  Xee{\\  ha'ie 
their  foundation  laid  before  birth,  behind  those  of  the  milk  set ; and  as 
they  are  found,  after  a time,  attached  to  the  sacs  of  the  tempora  y 
teeth,  (figs.  435,  439,)  it  was.  conceived  that  they  sprouted  or  shot  out 
from  these  latter.  This  has  been  disproved  by  the  ob.<ervations  of 
Goodsir,  who  has  shown  that  the  sacs  of  the  ten  anterior  permanent 
teeth  are  developed  from  the  dental  groove,  independently  of  the  milk 
sacs.  Recurring  to  the  follicular  stage  of  the  temporary  teeth,  w bich  is 
completed  about  tbe  fourteenth  week  (see  pp.  418-19),  it  will  be  remem- 
bered that  behind  each  milk  follicle  there  is  formed  a small  lunated 
recess,  (fig.  431,  5,  6;  and  fig.  436,')  similar  in  form  to  an  impressinn 
made  by  the  nail.  As  already  staled,  the  mucous  membrane  lining 
these  recesses  escapes  the  general  adhesion  of  the  lips  and  sides  of  the 
dental  groove,  so  that  when  the  latter  closes  they  are  converted  into  so 
many  cavities,  which  are  called  by  Mr.  Goodsir,  “ cavities  of  reserve,” 
(fig.  431,  7.')  Tliey  are  ten  in  number  in  each  jaw',  and  are  formed 


DEVELOPMENT  OF  THE  PERMANENT  TEETH. 


425 


Fig.  436. 


successively  from  before  backwards. 

They  ultimately  form  the  sacs  for  the 
incisor,  canine,  and  bicuspid  permanent 
teeth.  These  cavities  soon  elongate  and 
recede  into  the  substance  of  the  gum 
behind  the  milk  follicles,  above  and  be- 
hind in  the  upper  jaw,  below  and  be- 
hind in  the  lower  (8  to  12).  In  the 
mean  time,  a papilla  appears  in  the 
bottom  of  each  (that  for  the  central  in- 
cisor appearing  first,  at  about  the  sixth 
month),  and  one  or  more  folds  (8,  10), 
or  opercula,  as  in  the  case  of  the 
temporary  teeth,  are  developed  from 
the  sides  of  the  cavity,  and  by  their  sub- 
sequent union,  divide  it  into  two  por- 
tions, the  lower  portion  containing  the 
papilla,  and  now  forming  the  dental  sac 
and  pulp  of  the  permanent  tooth ; and 
the  upper  and  narrower  portion  being 
gradually  obliterated  in  the  same  man- 
ner as  the  primitive  groove  was  closed 
over  the  milk-sacs  (10,  11).  When 
these  changes  have  taken  place,  the 
permanent  sac  adheres  to  the  back  of 
that  for  the  temporary  tooth.  Both  of 
them  continue  then  to  grow  rapidly,  and 
after  a time  it  is  found  that  the  bony 
socket  not  only  forms  a cell  (fig.  437,  b') 
for  the  reception  of  the  milk  sac  {b),  but 
also  a small  posterior  recess  or  niche 
(a'),  for  the  permanent  sac  {a),  with 
which  the  recess  keeps  pace  in  its 
growth.  Confining  our  description 

now,  for  convenience,  to  the  lower  jaw  only,  it  is  found  that  at  length 
the  permanent  sac  so  far  recedes  in  the  bone  as  to  be  lodged  in  a 
special  osseous  cavity  at  some  distance  below  and  behind  the  milk 
tooth,  the  two  being  completely  separated  from  each  other  by  a bony 
partition  (figs.  437,  438,  439).  In  descending  into  the  jaw,  the  per- 
manent sac  (fig.  437,  a,  a,  a,)  acquires  at  first  a pear-shape,  and  is 
then  connected  with  the  gum  by  a solid  membranous  pedicle,  c.  The 
recess  in  the  jaw  has  a similar  form  ; it  presents  a cell,  d,  d,  for  con- 
taining the  sac  itself,  which  is  drawn  out  into  a long  canal,  c',c',  open- 
ing on  the  edge  of  the  jaw,  by  an  aperture  seen  behind  the  correspond- 
ing milk  tooth  (fig.  438,  c').  This  canal  lodges  the  above-mentioned 
membranous  pedicle.  The  permanent  tooth  (a),  which  is  developed 
from  its  dental  pulp  and  enamel  pulp,  in  the  manner  already  described, 
is  separated  from  the  socket  and  root  of  the  milk  tooth  by  a bony  par- 
tition, against  which,  as  well  as  against  the  root  of  the  milk  tooth,  b, 
just  above  it,  it  presses  in  its  rise  through  the  gum,  so  that  these  pans 
are  in  a greater  or  less  extent  absorbed.  When  this  has  proceeded 

36* 


Diagram  of  the  left  half  of  the  lower 
jaw  at  about  the  fourteenth  week,  slight- 
ly altered  from  Goodsir.  It  is  considera- 
bly magnified,  to  show  the  follicles  of 
the  milk  teeth  opened  out,  their  oper- 
cula, and  the  position  of  the  lunated 
recesses  behind  them,  from  which  the 
sacs  of  the  five  anterior  permanent  teeth 
are  developed.— 1 to  5.  Milk-teeth  folli- 
cles, numbered  in  their  order  of  appear- 
ance and  formation.  1.  First  molar. 
2 Canine.  3.  Central  incisor.  4 La- 
teral ditto.  5.  Second  molar,  a,  b.  A 
dotted  line  to  indicate  the  direction  in 
which  the  cross  sections,  represented  in 
fig.  432,  are  supposed  to  be  made;  such 
a section  carried  through  the  follicle  for 
the  second  incisor  would  correspond 
best  with  diagram  5 in  that  cut,  sup- 
posing the  opercula  and  the  lips  of  the 
follicles  were  not  opened  out.  f.  The 
cavity  of  the  follicle,  the  papilla  being 
hid.  o,  o.  The  opercula.  c.  Lunated 
depressions,  which  resist  the  subsequent 
adhesion  of  the  mucous  membrane,  and 
become  the  cavities  of  reserve  for  the 
permanent  teeth. 


426 


CALCIFICATION  OF  THE  PERMANENT  TEETH. 


far  enough,  the  milk  tooth  becomes  loosened,  falls  out  or  is  removed, 
and  the  permanent  tooth  then  takes  its  place.  The  milk  teeth  and  the 
permanent  teeth  are  said  by  Serres  to  be  supplied  by  two  ditferent 
arteries,  the  obliteration  of  the  one  going  to  the  temporary  teeth,  being 
regarded  by  him  as  the  cause  of  their  destruction,  but  of  this  there  is 
no  sufficient  proof. 

Fig.  437.  Fig.  438. 


Fig.  437.  After  Blake,  with  additions  in  outline. — These  figures  are  intended  to  show  the  re- 
lation between  the  sac  of  the  milk  tooth  and  that  of  the  corresponding  permanent  tooth,  together 
with  the  relation  of  both  to  the  substance  of  the  lower  jaw.  In  all  cases  a is  the  sac,  of  the  per- 
manent tooth,  c its  pedicle,  b that  of  the  milk  tooth,  or  the  milk  tooth  itself  a',  b',  and  o',  in  the 
diagrams  below  indicate  the  two  recesses,  with  the  intermediate  canal,  in  which  the  parts  a,  b, 
and  c,  are  lodged  in  the  jaw. 

Fig.  438.  After  Blake. — Position  of  a milk  and  a permanent  tooth  in  the  lower  jaw. — a.  Per- 
manent tooth.  b.  Milk  tooth,  or  its  socket,  c.  Orifice  of  a canal  in  the  bone,  which  transmits 
the  pedicle  of  a permanent  tooth  sac. 

The  six  posterior  (or  superadded")  permanent  teeth,  that  is,  the 
three  permanent  molars  on  each  side,  do  not  come  in  the  place  of 
other  teeth.  They  arise  from  successive  extensions  of  the  dental 
groove  carried  backwards  in  the  jaw,  posterior  to  the  milk  teeth,  and 
named  ^‘posterior  cavities  of  reserve.’’^ 

During  the  general  adhesion  of  the  dental  grooye  occurring  at  the 
fifteenth  week,  the  part  posterior  to  the  last  temporary  molar  follicle 
continues  unobliterated,  and  thus  forms  a cavity  of  reserve,  in  the 
fundus  of  which  a papilla  ultimately  appears,  and  forms  the  rudiment 
of  the  first  permanent  molar  tooth : this  takes  place  very  early,  viz.,  at 
the  sixteenth  week.  The  bottom  part  of  this  cavity  is  next  converted 
by  adhesion  into  a sac,  which  encloses  the  papilla,  whilst  its  upper 
portion  elongates  backwards  so  as  to  form  another  cavity  of  reserve,  j| 
in  which,  at  the  seventh  month  after  birth,  the  papilla  for  the  second 
molar  tooth  appears.  After  a long  interval,  during  which  the  sac  of 
the  first  permanent  molar,  and  its  contained  tooth,  has  acquired  great 
size,  (fig.  439,)  and  that  of  the  second  molar  has  also  advanced  con- 
siderably in  development,  the  same  changes  once  more  occur,  and 
give  rise  to  the  sac  and  papilla  of  the  wisdom  tooth,  the  rudiments  of 
which  are  visible  at  the  sixth  year.  The  subsequent  development  of 
the  permanent  molar  teeth  takes  place  from  these  sacs  just  like  that  of 
the  other  teeth. 

Calcification  begins  first  in  the  anterior  permanent  molar  teeth.  Its 
order  and  periods  are  thus  stated  for  the  upper  jaw,  the  lower  being  a 


ERUPTION  OF  THE  TEETH. 


427 


little  earlier.  First  molar,  five  or  six  months ; central  incisor,  soon 
after;  lateral  incisor  and  canine,  eight  or  nine  months;  two  bicuspids, 
two  years  and  over ; second  molar,  five  or  six  years;  third  molar,  or 
wisdom  tooth,  about  twelve  years. 

Eruption  of  the  Permanent  Teeth. — The  time  at  which  this  occurs  in 
regard  to  each  pair  of  teeth  in  the  lower  jaw  is  exhibited  in  the  sub- 
joined tables,  given  on  the  authority  of  Dr.  Blake  and  Mr.  Cartwright. 
The  corresponding  teeth  of  the  upper  jaw  appear  somewhat  later. 


BLAKE.  Years. 

Molar,  first 6^ 

Incisors,  central 7 

“ lateral . 8 

Bicuspids,  anterior 9 

“ posterior 10 

Canines  . . . ...  . 11  to  12 

Molars,  second 12  to  13 

“ third  (or  wisdom)  . 17  to  25 


CARTWRIGHT. 

Molar,  first 

Incisors,  central  inferior  . 
“ “ superior 

“ lateral  . . . 

Bicuspids,  anterior  . . 

Canines 

Bicuspids,  posterior  . . 

Molars,  second  . . . 

“ third  (wisdom) 


Years. 

5 to  7 

6—  8 

7—  9 

8— 10 
9 — 12 

10—12 
12—14 
17  — 25 


It  is  just  before  the  shedding  of  the  temporary  incisors,  i.  e.  about 
the  fifth  year,  that  there  is  the  greatest  number  of  teeth  in  the  jaws. 
At  that  period  there  are  all  the  milk  teeth,  and  all  the  permanent  set 
except  the  wisdom  teeth,  making  forty-eight. 

During  the  growth  of  the  teeth  the  jaw  increases  in  depth  and  length, 
and  undergoes  certain  changes  in  form.  In  the  child  it  is  shallow, 
(fig.  74,)  but  it  becomes  much  deeper  in  the  adult,  (fig.  73.)  In  the 
young  subject  the  alveolar  arch  describes  almost  the  segment  of  a 
circle  ; but  in  the  adult  the  curve  is  semielliptical.  The  increase  which 
takes  place  in  the  length  of  the  jaw  arises  from  a growth  behind  the 
position  of  the  milk  teeth,  so  as  to  provide  room  for  the  three  additional 
teeth  on  each  side,  belonging  to  the  permanent  set.  At  certain  periods 
in  the  growth  of  the  jaws  there  is  not  sufficient  room  in  the  alveolar 
arch  for  the  growing  sacs  of  the  permanent  molars ; and  hence  those 


Fig.  439, 


Part  of  lower  maxilla  of  a child,  containing  all  the  milk  teeth  of  the  right  side,  and  the  incisors 
of  the  left.  Sacs  and  pedicles  of  the  permanent  teeth  (except  the  wisdom  tooth),  exposed  by 
removing  part  of  the  bone  on  the  inside.  The  alveolar  canal  also  laid  open  to  show  the  course 
of  the  nerve.  The  large  sac  near  the  ramus  of  the  jaw  is  that  of  the  first  permanent  molar;  and 
above  and  behind  it,  is  seen  the  commencing  rudiment  of  the  second- molar. 


428 


ANALOGY  OF  TEETH  AND  BONE. 


parts  are  found  at  certain  stages  of  their  development  to  be  enclosed 
in  the  base  of  the  coronoid  process  of  the  lower  jaw,  (fig.  439,)  and  in 
the  maxillary  tuberosity  in  the  upper  jaw,  but  afterwards  successively 
assume  their  ultimate  position  as  the  bone  increases  in  length.  The 
space  taken  up  by  the  ten  anterior  permanent  teeth  exactly  corresponds 
with  that  which  had  been  occupied  by  the  ten  milk  teeth  ; the  difference 
in  width  between  the  incisors  of  the  two  sets  being  compensated  for 
by  the  smallness  of  the  bicuspids  in  comparison  with  the  milk  molars 
to  which  they  succeed.  Lastly,  the  angle  formed  by  the  ramus  and 
body  of  the  lower  jaw  differs  at  different  ages  ; thus  it  is  obtuse  in  the 
infant;  approaches  nearer  to  a right  angle  in  the  adult;  and  again 
becomes  somewhat  obtuse  in  old  age  (figs.  73,  74). 

Relation  of  the  blood-vessels  to  the  tooth. — There  is  no  evidence  that 
the  blood-vessels  send  branches  into  the  hard  substance.  The  red 
stain  sometimes  observed  in  the  teeth,  after  death  by  asphyxia,  and 
the  red  spots  otherwise  found  in  the  dentine,  are  due  to  the  imbibition 
of  blood  effused  on  the  surface  of  the  pulp.  The  dentine  formed  in 
young  animals  fed  upon  madder  is  tinged  with  that  colouring  matter, 
but  this  does  not  appear  to  take  place  when  the  growth  of  the  tooth 
is  completed.  Nevertheless  the  tubules  of  the  dentine  may  serve  to 
convey  through  its  substance  nutrient  fluid  poured  out  by  the  blood- 
vessels of  the  pulp.  The  teeth  are  sometimes  stained  yellow  in 
jaundice. 

Analogy  between  teeth  and  bone. — By  the  older  anatomists  the  teeth  were  con- 
sidered to  be  identical  with  bone,  and  were  described  as  parts  of  the  skeleton. 
Subsequently  to  this  they  were  compared  to  the  cuticular  tissues,  but  the  revela- 
tions of  the  microscope  have  tended  to  re-establish  the  former  opinion. 

The  enamel  is  the  only  part  which  has  no  analogy  with  bone.  The  crusta 
petrosa  is  in  all  respects  similar  to  bone ; and,  in  regard  to  the  dentine,  numerous 
points  of  resemblance  have  been  clearly  established.  Their  chemical  constituents 
are  the  same  in  nature,  although  they  differ  somewhat  in  their  proportions;  but  the 
bones  themselves  vary  in  this  respect  at  different  ages,  and  even  in  different  parts 
of  the  same  skeleton. 

The  tubuli  of  the  dentine  and  the  canaliculi  of  bone  though  differing  materially 
in  size  are  suggestive  one  of  the  other:  the  former  open  on  the  interior  of  the  pulp 
cavity,  and  the  latter  on  the  walls  of  the  Haversian  canals;  they  both  branch  out 
and  anastomose  by  their  finest  twigs;  and  both  communicate  with  minute  cells  or 
lacunae,  situate  in  the  surrounding  hard  substance,  which,  though  very  inconspi- 
cuous and  rare  in  the  human  tooth,  are  large  and  very  evident  in  the  teeth  of 
animals.  It  happens,  moreover,  that  in  the  bones  of  osseous  fishes  these  lacU'iae 
are  very  few  in  number. 

The  pulp  cavity  of  a tooth  with  its  vascular  contents,  and  the  Haversian  canals 
of  bone  with  their  nutrient  vessels,  may  be  justly  compared  together.  If  we  ima- 
gine a section  of  a group  of  coalesced  teeth,  the  pulp  cavities  with  their  surrounding 
tubuli  would  represent  a series  of  Haversian  canals  with  their  canaliculi;  and  in 
the  teeth  of  the  lower  animals,  as  already  mentioned,  these  tubuli  are  even  co,i- 
nected  with  numerous  lacunae.  The  inner  portion  of  the  tooth  of  the  walrus 
presents  a structure  analogous  to  what  is  here  imagined,  inasmuch  as  the  pulp 
cavity  is  divided  into  branches  which  resemble  Haversian  canals,  and  have 
radiating  tubuli  proceeding  from  them.  A similar  structure  is  seen  in  the  osteo- 
dentine  or  secondary  dentine  formed  within  the  human  teeth,  which  thus,  it  may 
be  remarked,  agrees  both  in  nature  and  position  with  the  core  of  the  walrus  tooth. 
It  is  stated  by  Mr.  Tomes  that  in  one  or  two  specimens  he  has  seen  vascular 
canals  traversing  the  dentine  of  the  fang  of  the  human  tooth,  proceeding  from  the 
pulp  cavity  outwards.  The  mode  of  growth  of  teeth  and  bone  is  evidently  not  so 
ditierent  as  was  formerly  supposed,  but  until  the  stages  of  this  process  in  both  are 


THE  TONGUE.  429 

better  understood,  it  would  be  premature  to  attempt  any  minute  comparison 
between  them  in  this  respect. 

It  has  been  offered  as  an  objection  to  the  assumed  analogy,  that  the  teeth, 
unlike  bones,  are  in  part  at  least  uncovered  by  soft  tissues;  but  true  bony  struc- 
tures are  sometimes  similarly  situated,  as  in  the  cutaneous  plates  of  the  sturgeon 
or  armadillo,  and  the  antlers  of  the  deer. 

Vibrios  of  the  mouth. — It  may  be  mentioned  here,  that  in  the  white  sordes  sur- 
rounding the  necks  of  the  teeth,  Leeuwenhoek  discovered  by  the  microscope 
numerous  minute  animalcules  of  the  Vibrio  kind  which  exhibit  very  active 
movements,  and  which  are  probably  produced  in  such  portions  of  vegetable  and 
animal  matters  used  as  food,  as  happen  to  adhere  between  the  margin  of  the  gums 
and  the  teeth. 

More  recently  Buhlmann  has  observed  fine  transparent  fibres  on  the  surface  of 
the  teeth,  espepially  where  tartar  had  been  allowed  to  gather  on  them.  These 
fibres  were  slightly  elastic,  but  consisted  of  some  sort  of  inorganic  substance, 
probably  of  a siliceous  nature,  for  they  resisted  the  action  of  the  strongest  acids 
and  alkalies. 

THE  TONGUE. 

The  tongue  is  the  proper  organ  of  taste,  and  owing  to  its  position 
in  the  floor  of  the  mouth,  and  to  its  great  mobility,  it  assists  in  masti- 
cation and  deglutition,  and  also  in  articulation. 

In  its  general  form,  the  tongue  is  adapted  to  the  interval  between 
the  two  halves  of  the  lower  jaw  ; thus  it  is  wider,  and  at  the  same 
time  thicker,  at  its  base  or  root,  which  is  turned  backwards,  and  nar- 
rower and  thinner  at  its  apex  or  tip^  which  is  directed  forwards 
against  the  inner  surface  of  the  lower  incisor  teeth.  The  base  and  the 
posterior  part  of  the  under  surface  of  the  tongue  are  attached;  but  the 
fore  part  of  its  under  surface,  the  sides  or  borders,  the  upper  surface 
and  the  tip,  are  free. 

The  attachments  of  the  tongue  are  partly  muscular,  or  fibro-cellular, 
and  in  port  consist  of  reflections  of  the  mucous  membrane  of  the 
mouth.  Thus,  it  is  connected  to  the  soft  palate  by  the  palato-glossus 
muscle,  to  the  styloid  process  by  the  stylo-glossus,  to  the  hyoid  or 
lingual  bone  by  the  hyoglossus  and  some  fibro-cellular  tissue,  and, 
lastly,  to  the  inferior  maxilla  by  the  genio-hyo-glossus  (fig.  444). 

By  means  of  the  mucous  membrane,  the  tongue  is. connected  behind 
with  the  epiglottis ; three  folds,  named  the  glosso-epiglottic  folds  or 
frEBnula,  of  which  the  middle  one  is  the  larger,  pass  backwards  from 
the  one  to  the  other  (figs.  440,  444).  (3n  each  side  of  these,  the 

tongue  is  connected  with  the  pharynx,  and  farther  outwards  with  the 
soft  palate,  by  the,  two  arches  or  pillars  of. the  fauces  (fig.  441,  r,  i). 
Lastly,  from  the  under  surface  of  the  tongue,  at  the  sides  and  also  in 
front,  the  mucous  membrane  is  reflected  over  the  sublingual  gland  to 
the  inner  surface  of  the  gums  of  the  low'er  jaw;  and  it  forms  in  the 
middle  line,  in  front,  a median  fold  called  the  frcenum  linguce. 

The /ree  surface  of  the  tongue. — The  free  portion  of  the  under 
surface  of  the  tongue  is  covered  by  a thin  and  smooth  mucous  mem- 
brane. In  front,  beneath  the  tip  of  the  organ,  it  is  marked  by  a 
median  line  continuous  with  the  fraenum  linguce.  Near  this  line,  on 
each  side,  the  ranine  vein  may  be  distinctly  seen  through  the  mucous 
membrane,  and  close  to  it  lies  the  artery  pf  the  same  name.  The 
ducts  of  the  right  and  left  submaxillary  glands  also  end  in  the  floor  of 


430 


PAPILLAE  OF  THE  TONGUE. 


the  mouth,  one  on  each  side  of  tlie  frasnnm;  and  further  back,  in  the 
groove  between  the  sides  of  the  tongue  and  the  lower  jaw,  are  found 
the  orifices  of  the  several  ducts  belonging  to  the  sublingual  ^ands. 

The  rounded  bordci's  of  the  tongue  b^ecome  gradually  thinner  in 
approaching  the  apex  of  the  organ.  The  mucous  membrane,  in 
passing  over  them  from  below,  gradually  acquires  the  papillary  cha- 
racter of  that  on  the  upper  surface. 

The  upper  surface  or  dorsum  of  the  tongue  (fig.  440)  is  convex  in 
its  general  outline,  and  is  marked  along  the  middle  in  its  whole  length 
by  a slight  furrow  called  the  raphe, ^ which  indicates  its  bilateral  sym- 
metry. About  half  an  inch  from  the  base  of  the  tongue,  the  raphe 
often  terminates  in  a depression,®  closed  at  the  bottom,  which  is 
called  \\\Q  foramen  cacum  (Morgagni),  and  in  which  several  mucous 
glands  and  follicles  open. 

The  upper  surface  of  the  tongue  is  covered  all  over  with  numerous 


[Fig.  440. 


[Fig.  441. 


[Fig.  440.  The  tongue  with  its  papillae.  I.  The  raphe, 
which  in  some  tongues  bifurcates  on  the  dorsum  of  the 
organ,  as  in  the  figure.  2,  2.  The  lobes  of  the  tongue.  The 
rounded  eminences  on  this  part  of  the  organ,  and  near  ils 
tip  are  the  papillse  fungiformes.  'l'he«maller  papillae,  among 
which  the  former  are  dispersed,  are  the  papillae  conicae  and 
filiformes.  3.  The  lip  of  the  tongue.  4,4.  Its  sides,  on 
which  are  seen  the  lamellated  and  fringed  papillte.  5,5. 
The  V-shaped  row  of  papillte  circumvallalae.  6.  The  fora- 
men cseciim.  7.  The  mucous  glands  of  tlie  roots  of  the 
tongue.  8.  The  epiglottis.  9,  9.  The  frmiia  epiglottidis. 
10,  10.  The  greater  cornua  of  the  os  hyoides. — W.] 

[Fig.  441.  Various  forms  of  the  conical  compound  pa- 
pillae, deprived  of  their  epithelium: — a,  h,  and  especially  c, 
are  the  best  marked,  and  were  provided  with  the  stillest 
and  longest  epithelium;  their  simple  papillte  are  more  acu- 
minated. d,  approaches  the  fungiform  variety : e,/,  come  near  the  simple  papillae. — Magnified 
20  diameters. — Todd  and  Bowman.] 


projections  or  eminences  named  papillce.  They  are  found  also  upon 
the  tip  and  free  borders,  where,  however,  they  gradually  become 
smaller,  and  disappear  towards  its  under  surface.  These  papillae  are 
distinguished  into  three  orders,  varying  both  in  size  and  form. 

The  large  papillae  (papillae  maximae,  vallatae,  vel  circumvpllatae), 
eight  to  fifteen  in  number,  (?  ®,)  are  found  on  the  back  part  of  the 
tongue,  arranged  in  two  rows,  which  run  obliquely  backwards  and 
inwards,  and  meet  towards  the  foramen  caecum,  like  the  arms  of  the 


letter  V.  They  are  situated  in  cup-like  cavities  or  depressions  of  the 
mucous  membrane,  and  are  shaped  like  an  inverted  cone,  of  which 
the  apex  is  attached  to  the  bottom  of  the  cavity,  and  the  broad  flat- 
tened base  appears  on  the  surface.  They  are  therefore  surrounded,  as 
it  were,  by  a circular  furrow  or  trench,  around  which  again  is  an 


PAPILLA  OF  THE  TONGUE. 


431 


annular  elevation  of  the  mucous  membrane,  covered  with  the  smaller 
papillae.  The  exposed  surface  of  the  papillae  vallatae  is  beset  with 
numerous  smaller  papillae  or  filaments,  and  in  some  of  them  there  is 
found  a central  depression  into  which  mucous  follicles  open. 

The  middle-sized  (papillae  mediae,  capitatae,  vel  fungiformes),  more 
numerous  than  the  last,  are  little  rounded  eminences  scattered  over  the 
middle  and  fore  part  of  the  dorsum  of  the  tongue  ; but  they  are  found 
in  greater  numbers  and  closer  together  near  and  upon  the  apex.  They 
are  easily  distinguished  by  their  more  intensely  red  colour.  They  are 
narrow  at  their  point  of  attachment,  but  are  gradually  enlarged  to- 
wards their  free  extremities,  which  are  blunt  and  rounded,  and  are 
covered  with  smaller  filamentous  appendages  or  papillae  (fig.  441,  d). 

The  smallest  papillce  (papillae  minimae),  which  include  the  papillce 
conic(z  and  Jiliformes,  are  the  most  numerous  of  all.  They  are  minute, 
conical,  tapering,  or  cylindrical  processes,  which  are  densely  packed 
over  the  greater  part  of  the  dorsum  of  the  tongue,  towards  the  base 
of  which  they  gradually  disappear.  They  are  arranged  in  lines, 
which  correspond  at  first  with  the  oblique  direction  of  the  two  ridges 
of  the  papillae  vallatae,  but  gradually  become  transverse  towards  the 
tip  of  the  tongue.  At  the  sides  they  are  longer  and  more  filiform,  and 
arranged  in  parallel  rows,  perpendicular  to  the  border  of  the  tongue. 
The  filiform  papillae  are  paler  and  provided  with  a thicker  epithelium 
than  the  other  kinds  ; and  they  are  also  covered  with  small  and  rather 
stiff  secondary  papillae.  Interspersed  between  these  three  kinds  of 
papillae,  and  also  at  the  back  part  of  the  tongue  behind  the  papillae 
vallatae,  there  are  found  numerous  minute  projecting  filaments,  con- 
cealed by  epithelium,  and  scarcely  visible  until  that  be  removed. 
(Todd  and  Bowman.) 

These  different  kinds  of  papillae  are  highly  vascular  and  sensitive 


432 


PAPILLA  OF  THE  TONGUE. 


belongs  to  the  squamous  kind  (fig.  442,  B,  d) : over  the  filiform  papillaB 
it  is  denser  than  elsewhere,  and  presents  an  imbricated  arrangement; 
on  some,  it  forms  a lash  or  pencil  of  fine  fibres ; and,  on  others,  it  ap- 
proaches closely  in  character  and  structure  to  hairs  (fig.  443).  The 
papillae  are  undoubtedly  the  parts  chiefly  concerned  in  the  special 
sense  of  taste;  but  they  also  possess,  in  a very  acute  degree,  common 
tactile  sensibility  ; and  the  filiform  papillae,  armed  with  their  denser 
epithelial  covering,  serve  a mechanical  use  in  the  action  of  the  tongue 
upon  the  food. 

The  mucous  membrane  of  the  tongue  is  provided  with  numerous 


[Fig.  443. 


fi  7,  A c c( 


A.  Vertical  section  near  the  middle  of  the  dorsal  surface  of  the  tongue  : — a,  a.  Fungiform 
papillaj.  h.  Filiform  papilloe,  with  their  hair-like  processes,  c.  Similar  ones  deprived  of  their 
epithelium. — Magnified  3 diameters. 

B.  Filiform  compound  papillse  : — a.  Artery,  v.  Vein.  c.  Capillary  loops  of  the  secomlr.r)’ 

fiapilloe.  b.  Line  of  basement  membrane,  d.  Secondary  papill®,  deprived  of  e,  e,  the  epi'.he- 
ium.  f.  Hair-like  processes  of  epithelium  capping  the  simple  papill®. — Magnified  25  diameters. 
g.  Separaied  nucleated  particles  of  epithelium,  magnified  300  diameters. 

1,  2.  Ha  irs  found  on  the  surface  of  the  tongue.  3,  4,  5.  Ends  of  hair-like  epithelial  proceaees, 
showing  varieties  in  the  imbricated  arrangement  of  the  particles,  but  in  all  a coalescence  of  ihe 
particles  towards  the  point.  5,  encloses  a soft  hair. — Magnified  160  diameters. — Todd  and 
Bowman.]  " 

follicles  and  glands.  The  folicles,  simple  and  compound,  are  scattered 
over  the  surface ; but  the  rounded  conglomerate  glands,  called  lingual 
glands,  are  collected  about  the  posterior  part  of  the  dorsum  of  thel 
tongue,  near  the  papillae  vallatae  and  foramen  caecum,  into  which  the 


MUSCLES  OF  THE  TONGUE. 


433 


ducts  of  several  of  these  glands  open.  Other  small  glands  are  found 
also  beneath  the  mucous  membrane  of  the  borders  of  the  tongue. 
There  is,  in  particular,  a small  group  of  these  glands  on  the  under 
surface  of  the  tongue  near  the  apex.  They  are  there  aggregated  into 
a little  oblong  mass,  out  of  which  several  ducts  proceed  and  open 
separately  on  the  mucous  membrane.  This  little  gland,  or  group  of 
glands,  was  pointed  out  by  Blandin,  and  has  been  more  lately  described 
and  figured  by  Nuhn. 

The  substance  of  the  tongue  is  chiefly  composed  of  muscular  fibres, 
running  in  different  but  determinate  directions ; hence  the  variety 
and  regularity  of  its  movements,  and  its  numerous  changes  of  form. 
Many  of  the  contractile  fibres  of  the  tongue  belong  to  muscles  w'hich 
enter  at  its  base  and  under  surface,  and  attach  it  to  other  parts : these, 
which  have  been  already  enumerated,  are  called  the  extrinsic  muscles 
of  the  tpngue,  and  have  been  elsewhere  described  (vol.  i.  pp.  353-4, 
and  366).  Other  bands  of  fibres  constitute  the  intrinsic  or  proper 
muscles,  and  are  arranged  in  two  principal  longitudinal  layers,  with 
a large  intervening  mass  of  transverse  fibres. 

The  first,  superior,  or  superficial  longitudinal  layer,  named  lingualis 
superficialis,  is  placed  on  the  upper  surface  of  the  tongue,  immediately 
beneath  the  raucous  membrane,  and  is  traceable  from  the  apex  of  the 
organ  backwards  to  the  hyoid  bone.  The  individual  fibres  do  not 
run  the  whole  of  this  distance,  but  are  attached  at  intervals  to  the 
submucous  and  glandular  tissues.  The  entire  layer  becomes  thinner 
towards  the  base  of  the  tongue,  near  which  it  is  overlapped  at  the  sides 
by  a thin  plane  of  oblique  or  nearly  transverse  fibres  derived  from  the 
palato-glossus  and  hyo-glossus  muscles. 

The  inferior  or  deep  longitudinal  layer  of  muscular  fibres,  placed 
at  the  under  surface  of  the  tongue,  is  i\\e  lingualis  nnuscle,  properly  so 
called,  of  Douglas,  Albinus,  and  other  anatomists,  and  is  sometimes 
described  as  the  lingualis  inferipr.  It  consists  of  a rounded  muscular 
band,  extending  'along  the  under  surface  of  the  tongue  from  base  to 
apex,  and  lying  outside  the  genio-hyO-glossus,  between  that  muscle  and 
the  hyo-glossus.  Posteriorly,  some  of  its  fibres  are  lost  in  the  sub- 
stance of  the  tongue,  and  others  reach  the  hyoid  bone.  In  front,  having 
first  been  joined,  at  the  anterior  border  of  the  hyo-glossus  muscle,  by 
fibres  from  the  stylo-glossus,  it  is  prolonged  beneath  the  border  of  the 
tongue  as  far  as  its  point. 

The  transverse  muscular  fibres  of  the  tongue  (lingualis  transversus) 
form  together  with  the  intermixed  fat  a considerable  part  of  its  sub- 
stance. They  are  found  in  the  interval  between  the  upper  and  lower 
longitudinal  muscles,  and  they  intersect  extensively  with  the  other 
muscular  fibres.  Passing  across  each  way  from  the  median  plane  of 
the  tongue,  they  reach  its  dorsum  and  borders ; and  they  are  con- 
sidered by  some  anatomist's  to  take  a distinct  origin  from  a median 
fibrous  partition  to  be  presently  described.  In  proceeding  outward 
from  the  middle  line,  these  transverse  fibres  have  also  an  inclination 
upwards,  so  that  they  form  a series  of  curves,  having  the  concavity 
turned  upw'ards.  Other  transverse  fibres,  according  to  Theile,  arise 
from  the  hyoid  bone,  betw'.een  the  attachment  of  the  two  genio-hyo-glossi 

VOL.  II.  37 


434 


THE  PALATE. 


muscles,  and  run  outwards  and  upwards  on  each  side  to  reach  the 
border  of  the  tongue.  All  these  fibres  intersect,  by  bundles,  the  as- 
cending fasciculi  of  the  genio-hyo-glossus  and  hyo-glossus  muscles. 

Special  vertical  fibres  have  also  been  described  by  Gerdy  and  Cru- 
veilhier  as  existing  in  the  tongue.  Fibres  having  a vertical  direction 
may  undoubtedly  be  seen  on  making  perpendicular  sections  of  this 
organ  in  man ; but  it  is  the  opinion  of  Theile,  that  those  seen  in  a 
longitudinal  vertical  section  belong  to  the  ascending  fasciculi  of  the 
genio-hyo-glossus,  or  hyo-glossus,  and  the  additional  vertical  fibres 
which  appear  in  a similar  section  made  transversely  belong  tC  the 
oblique  bundles  of  the  transverse  system  of  fibres. 

These  intrinsic  muscles  of  the  tongue  serve  principally  to  alter  its 
form,  retracting  or  elongating  it  in  various  directions.  The  superfi- 
cial longitudinal  fibres  can  also  curve  the  tip  of  the  tongue  upwards, 
and  the  lower  set  can  curve  it  downwards.  Betw'een  the  several 
layers  and  bundles  of  muscular  fibres,  there  is  always  found  a consi- 
derable quantity  of  a soft  fatty  tissue,  and  also  a very  fine  cellular 
web. 

In  the  median  line,  towards  the  base  of  the  tongue  and  in  the  midst 
of  the  muscular  substance,  there  is  a vertical  layer  of  fibrous  tissue, 
which  forms  a partial  septum  between  the  two  halves'of  the  organ. 
This  is  connected  behind  with  the  hyoid  bone;  and  in  front,  it  is  lost 
between  the  muscles.  It  is  w'ell  known,  that,  in  animals  of  the  dog 
tribe,  a fusiform  fibro-cartilage  is  found  in  the  middle  of  the  tongue 
near  its  under  surface;  and  Blandin  has  described  a thin  fibro-cartila- 
ginous  lamina  in  the  human  tongue  as  forming  a part  of  the  vertical 
median  septum,  but,  according  to  Krause,  in  most  instances  there  is 
no  trace  of  such  a structure.  The  last  writer  further  states,  that, 
when  it  does  exist,  it  is  about  three  or  four  lines  in  height  and  length; 
its  borders  are  irregular;  its  two  sides  serve  as  points  of  insertion  to 
muscular  fibres ; and  it  is  often  imperfect,  or  pierced  with  small 
holes. 

The  arteries  of  the  tongue  are  derived  from  the  lingualis,  with  some 
small  branches  from  the  facial  and  ascending  pharyngeal.  The  veins 
for  the  most  part  correspond. 

The  nerves  of  the  tongue  (exclusive  of  branches  from  the  sympa- 
thetic nerves)  are  three ; viz.,  the  lingual  or  gustatory  branch  of  die 
fifth  pair,  which  supplies  the  papillae  and  mucous  membrane  of  the 
fore  part  and  sides  of  the  tongue;  the  lingual  branch  of  the  glosso-pha- 
ri/ngeal,  which  sends  filaments  to  the  mucous  membrane  at  the  base 
of  the  tongue,  and  especially  to  the  papillae  vallatae ; and,  lastly,  the 
hypoglossal  nerve,  which  is  distributed  to  the  muscles. 

THE  palate. 

The  roof  of  the  mouth  is  formed  by  the  palate,  which  consists  of 
two  portions ; the  fore  part  being  named  the  hard  palate,  and  the 
back  part,  the  soft  palate. 

The  osseous  framework  of  the  hard  palate,  a,  fig.  444,  the  general 
form  and  component  pieces' of  which  have  been  described,  (vol.  i.  fig. 
16G,)  covered  by  the  periosteum,  and  by  the  lining  membrane  of  the 


THE  SOFT  PALATE. 


435 


mouth,  which  adhere  intimately  together.  The  mucous  membrane, 
which  is  continuous  with  that  of  the  gums,  is  thick,  dense,  rather  pale, 
and  much  corrugated,  especially  in  front  and  at  the  sides;  but  is 


Fig.  444. 


Median  section  of  the  nose,  mouth,  pharynx,  and  larynx. — a.  Septum  of  the  nose ; below  it, 
is  the  section  of  the  hard  palate,  b.  The  tongue,  c.  Section  of  velum  pendulum  palati.  d,d. 
Lips.  u.  Uvula,  r.  Anterior  arch  or  pillar  of  fauces,  i.  Posterior  arch.  (.  Tonsil,  p.  Pha- 
rynx. h.  Hyoid  bone.  h.  Thyroid  cartilage,  n.  Cricoid  cartilage,  s.  Epiglottis,  v.  Glottis. 
1.  Posterior  opening  of  nares.  3.  Isthmus  faucium.  4.  Superior  opetiing  of  larynx.  5.  Passage 
into  (Esophagus.  6.  Mouth  of  right  Eustachian  tube. 

smoother,  thinner,  and  of  a deeper  colour  behind.  Along  the  middle 
line  is  a ridge  or  raphe,  ending  in  front  in  a small  eminence,  which 
corresponds  with  the  lower  opening  of  the  anterior  palatine  canal,  and 
receives  the  terminal  filaments  of  the  naso-palatineand  anterior  palatine 
nerves.  The  membrane  of  the.  hard  palate  is  provided  with  many 
muciparous  glands,  which  form  a continuous  layer  between  the  mem- 
brane and  the  bone,  and  it  is  covered  with  a squamous  epithelium. 

The  soft  palate  (velum  pendulum  palati : c)  is  formed  of  mucous 
membrane  enclosing  muscular  fibres  and  numerous  glands.  It  con- 
stitutes an  incomplete  and  movable  partition  between  the  mouth 
and  the  pharynx.  It  is  attached  to  the  posterior  border  of  the 
hard  palate,  the  membranous  portion  of  which  is  thus  continued 
obliquely  downwards  and  backwards.  At  the  sides,  the  soft  palate  is 
also  connected  with  the  lining  membrane  of  the  mouth  and  pharynx. 
Its  lower  border  is  free,  and  has  depending  from  its  middle  a red 
conical  process  called  the  uvula,  u.  From  the  base  of  the  uvula,  on 
each  side,  the  free  margin  of  the  velum  forms  two  arched  folds,  which 
pass  outwards  and  then  downwards,  one  behind  the  other.  These 
are  the  anterior  and  posterior  arches  of  the  palate.  The  anterior 
arches,  r,  run  downwards  and  forwards  to  the  sides  of  the  tongue 


436 


THE  TONSILS. 


near  its  base ; whilst  the  posterior  arches,  i,  which  approach  more 
closely  together,  and  may  therefore  be  easily  seen  behind  the  anterior 
arches  on  looking  into  the  throat,  run  downwards  and  backwards  to 
the  sides  of  the  pharynx.  Between  the  anterior  and  posterior  palatine 
arch  of  each  side,  there  is  therefore  a triangular  recess,  and  in  this 
the  corresponding  tonsil  or  amygdala,  t,  is  placed.  The  interval  be- 
tw'een  the  palatine  arches  of  the  two  sides,  bounded  above  by  the  free 
margin  of  the  soft  palate,  and  below  by  the  tongue,  is  the  passage 
leading  from  the  mouth  into  the  pharynx,  named  the  isthmus  faucium, 
(before  ^,)  and  the  arches  are  called  the  pillars  of  the  fauces. 

The  anterior  or  under  surface  of  the  velum,  which  is  visible  in  the 
mouth,  is  concave.  The  mucous  membrane,  continuous  with  that  of 
the  hard  palate,  is  thinner  and  darker  than  it,  and  is  covered  with  a 
scaly  epithelium.  It  is  marked  by  a slight  median  ridge  or  raphe, 
which  descends  towards  the  uvula,  and  indicates  the  original  separa- 
tion of  the  velum  into  two  lateral  halves. 

The  posterior  surface  of  the  soft  palate,  slightly  convex  or  arched, 
is  continuous  above  with  the  floor  of  the  posterior  nares.  It  is  slightly 
elevated  along  the  middle  line,  opposite  to  the  uvula.  The  greater 
portion  of  its  mucous  membrane,  as  well  as  that  of  the  free  margin  of 
the  velum,  is  covered  with  a squamous  epithelium  ; but  quite  at  its 
upper  portion,  near  the  orifice  of  the  Eustachian  tube,®  the  epithelium 
is  columnar  and  ciliated. 

On  both  surfaces  of  the  velum  are  found  numerous  small  glands, 
called  the  palatine  glands.  They  particularly  abound  on  the  upper 
surface,  where  they  form  quite  a glandular  layer ; they  are  also  very 
abundant  in  the  uvula. 

Muscles. — Between  the  two  layers  of  mucous  membrane  of  which 
the  velum  is  composed,  are  situated  the  muscles  of  the  soft  palate. 
They  consist  of  five  muscles  on  each  side ; — two  superior,  viz.,  the 
levator  palati  and  the  circumflexus  or  tensor  palati ; two  inferior,  viz., 
the  palato-glossus  and  the  palato-pharyngeus, — of  which  the  former  is 
enclosed  in  the  anterior  palatine  arch,  and  the  latter  in  the  posterior 
arch  ; and  lastly,  one  median,  which  descends  into  the  uvula,  and 
with  the  muscle  of  the  opposite  side  forms  the  azygos  uvulas.  The 
description  of  these  muscles,  and  of  their  action,  will  be  found  at  vol. 
i.  p.  365. 

THE  TONSILS. 

The  tonsils  (tonsillae,  amygdalae)  are  two  prominent  bodies,  which 
occupy  the  recesses  formed,  one  on  each  side  of  the  fauces,  i,  between 
the  anterior  and  posterior  palatine  arches. 

They  are  usually  about  six  lines  in  length,  and  four  in  width  and 
thickness ; but  they  vary  much  in  size  in  different  individuals. 

The  outer  side  of  the  tonsil  is  connected  with  the  inner  surface  of 
the  superior  constrictor  of  the  pharynx,  and  approaches  very  near  to 
the  internal  carotid  artery.  Considered  in  relation  to  the  surface  of 
the  neck,  the  tonsil  corresponds  to  the  angle  of  the  lower  jaw,  where 
it  may  be  felt  beneath  the  skin  when  it  is  enlarged.  Its  inner  surface, 
projecting  into  the  fauces  between  the  palatine  arches,  presents  from 


THE  SALIVARY  GLANDS. 


437 


twelve  to  fifteen  orifices,  which  give  it  a perforated  appearance. 
These  orifices  lead  into  recesses  in  the  substance  of  the  tonsil,  from 
which  other  and  smaller  orifices  conduct  still  deeper  into  numerous 
compound  crypts  or  follicles,  the  whole  being  lined  with  continuations 
of  the  buccal  mucous  membrane.  The  tonsils  therefore  consist  of 
groups  of  compound  muciparous  crypts.  They  yield  a mucous  fluid, 
which  lubricates  the  fauces.  The  tonsils  receive  a very  large  supply 
of  blood  from  many  sources,  viz.,  from  the  tonsillar  and  palatine 
branches  of  the  facial  artery,  and  from  the  descending  palatine,  the 
ascending  pharyngeal  and  the  dorsalis  linguas.  Its  veins  are  nume- 
rous, and  enter  the  tonsillar  plexus  on  its  outer  side.  Its  nerves  come 
from  the  glosso-pharyngeal  nerve,  and  from  the  fifth  pair. 

THE  SALIVARY  GLANDS. 

The  saliva,  which  is  poured  into  the  mouth,  and  there  mixed  with 
the.  food  during  mastication,  is  secreted  by  three  pairs  of  glands, 
named,  from  their  respective  situations,  the  parotid,  submaxillary,  and 
sublingual  glands.  Agreeing  in  their  general  physical  characters  and 
minute  structure,  they  differ  in  their  size,  form,  and  position. 

The  Parotid  Gland. 

The  parotid  gland,  (-ira^a,  and  ouj,  wrof,)  so  called  from  being  placed 
near  the  ear,  is  the  largest  of  the  three  salivary  glands.  It  lies  on  the 
side  of  the  face,  in  front  of  the  ear,  and  beneath  the  skin  ; but  it  ex- 
tends deeply  into  the  space  behind  the  ramus  of  the  lower  jaw.  Its 
weight  varies  from  five  to  eight  drachms. 

Its  outer  surface  is  rounded  and  lobulated,  and  is  covered  by  the 
skin  and  fascia,  and  partially  by  the  platysma  muscle.  It  is  bounded 
above  by'  the  zygoma,  below  by  a line  drawn  backwards  from  the 
lower  border  of  the  jaw  to  the  sterno-mastoid  muscle,  and  behind  by 
the  external  meatus  of  the  ear,  the  mastoid  process,  and  sterno-mas- 
toid muscle.  Its  anterior  border,  which  is  in  contact  with  the  ramus 
of  the  lower  jaw,  is  less  distinctly  defined,  and  advances  forwards  to 
a variable  extent  on  the  masseter  muscle.  It  is  from  this  anterior 
border  of  the  gland  that  the  excretory  duct  passes  off;  and  there  is 
sometimes  found  in  connexion  with  the  duct,  and  lying  upon  the  mas- 
seter muscle,  a small  process  or  a separated  portion  of  the  gland, 
which  is  called  glandula  socia  {soda  parotidis).  On  trying  to  raise 
the  parotid  gland  from  its  position,  it  is  found  to  extend  far  inwards, 
between  the  mastoid  process  and  the  ramus  of  the  jaw,  towards  the 
base  of  the  skull,  and  to  be  intimately  connected  with  several  deep- 
seated  parts.  Thus,  above,  it  reaches  into  and  occupies  the  posterior 
part  of  the  glenoid  cavity;  behind  and  below,  it  touches  the  digastric 
muscle,  and  rests  on  the  styloid  process  and  styloid  muscles;  and,  in 
front,  under  cover  of  the  ramus  of  the  jaw,  it  advances  a certain  dis- 
tance between  the  external  and  internal  pterygoid  muscles. 

The  internal  carotid  artery  and  internal  jugular  vein  are  close  to  the 
inner  or  deep  surface  of  the  gland.  The  external  carotid  artery,  ac- 
companied by  the  temporal  and  internal  maxillary  veins,  passes 
through  the  parotid  gland,  and  in  that  situation  gives  origin  to  the 

37* 


438 


TEIli  SUBMAXILLARY  GLAND. 


anterior  auricular,  transverse  facial,  temporal,  and  internal  maxillary 
arteries.  The  gland  is  also  traversed  by  the  facial  nerve,  which 
divides  within  its  substance,  and  by  branches  of  the  great  auricular 
nerve. 

The  'parotid  duct,  named  also  the  Stenonian  duct,  appears  at  the 
anterior  border  of  the  gland,  about  one  finger’s  breadth  below  the 
zygoma,  and  runs  forwards  over  the  masseter  muscle,  accompanied 
by  the  socia  parotidis,  when  that  accessory  portion  of  the  gland  exists, 
and  receiving  its  ducts.  At  the  anterior  border  of  the  masseter,  the 
duct  turns  inwards  through  the  fat  of  the  cheek  and  pierces  the  buc- 
cinator muscle;  and  then,  after  running  for  a short  distance  obliquely 
foiwvards  beneath  the  mucous  membrane,  opens  upon  the  inner  sur- 
face of  the  cheek,  by  a small  orifice  opposite  the  crown  of  the  second 
molar  tooth  of  the  upper  jaw.  Its  direction  across  the  face  may  be 
indicated  by  a line  drawn  from  the  lower  margin  of  the  concha  of 
the  ear  to  midway  between  the  red  margin  of  the  lip  and  the  ala  of 
the  nose.  The  length  of  the  Stenonian  duct  is  about  two  inches  and 
a half,  and  its  thickness  about  one  line  and  a half.  Where  it  perfo- 
rates the  buccinator,  its  canal  is  as  large  as  a crow-quill,  but  its  ori- 
fice, which  is  the  smallest  part  of  it,  will  only  admit  a very  fine  probe. 
The  duct  is  surrounded  by  cellular  tissue,  and,  besides  this,  consists 
of  an  external  dense  and  thick  fibrous  coat,  in  which  contractile 
fibres  are  described,  and  of  an  internal  mucous  tunic,  which  is  con- 
tinuous with  that  of  the  mouth,  but  which  is  covered,  from  the  orifice 
of  the  duct  as  far  as  to  the  smallest  branches,  with  a columnar  epithe- 
lium. 

The  parotid  gland  belongs  to  the  class  of  compound  cellular  glands, 
and  consists  of  numerous  flattened  lobes,  held  together  by  the  ducts 
and  vessels,  and  by  a dense  cellular  web,  which  is  continuous  with 
the  fascia  upon  its  outer  surface;  but  the  gland  has  no  special  or 
proper  coat.  The  lobes  are  again  divided  into  lobules,  each  of  which 
consists  of  the  branched  terminations  of  the  duct,  and  of  vessels, 
nerves,  and  fine  cellular  tissue.  The  ducts  terminate  in  closed  vesi- 
cular extremities,  about  ’f^ch  or  more  in  diameter,  and 

having  capillary  vessels  ramifying  upon  them. 

The  vessels  of  the  parotid  gland  enter  and  leave  it  at  all  points. 
The  arteries  are  derived  directly  from  the  external  carotid,  and  from 
those  of  its  branches  which  pass  through  or  near  the  gland.  The 
veins  correspond.  The  absorbents  join  the  deep  and  superficial  set 
in  the  neck ; and  there  are  often  one  or  more  lymphatic  glands  em- 
bedded in  the  substance  of  the  parotid.  The  nerves  come  from  the 
sympathetic  (carotid  plexus,)  and  also,  it  is  said,  from  the  facial  and 
the  superficial  temporal  and  great  auricular  nerves. 

The  Submaxillary  Gla-nd. 

The  submaxillary  glaifid,  the  next  in  size  to  the  parotid  gland,  is  ot 
a rounded  form,  and  weighs  about  2 or  2|  drachms.  It  is  situated 
immediately  below  the  base  and  the  inner  surface  of  the  inferior  max- 
illa, and  above  the  digastric  muscle.  In  this  position  it  is  covered  in 
by  the  skin  and  the  platysma  myoides,  and  its  inner  surface  rests  on 


THE  SUBLINGUAL  GLAND. 


439 


the  my]o-hyoid,  hyoglossus,  and  stylo-glossus  muscles;  above,  it  cor- 
responds with  a depression  on  the  inner  surface  of  the  jaw-bone ; and 
it  is  separated  behind  from  the  parotid  gland,  merely  by  the  stylo- 
maxillary membrane.  The  facial  artery,  just  before  it  mounts  over 
the  jaw-bone,  lies  in  a groove  upon  the  back  part  and  the  upper  border 
of  the  gland. 

The  duct  of  the  submaxillary  gland,  named  the  V/hai-tonian  duct, 
which  is  about  two  inches  in  length,  passes  off  from  the  gland,  to- 
gether with  a thin  process  of  the  glandular  substance,  around  the  pos- 
terior border  of  the  mylo-hyoid  muscle,  and  then  runs  forwards  and 
inwards  above  that  muscle,  between  it  and  the  hyoglossus  and  genio- 
hyoglossus,  and  beneath  the  sublingual  gland,  to  reach  the  side  of  the 
frsenum  linguae.  Here  it  terminates,  close  to  the  duct  of  the  opposite 
side,  by  a narrow  orifice,  which  opens  at  the  summit  of  a small 
caruncle  seen  beneath  the  tongue.  The  structure  of  this  gland  is  like 
that  of  the  parotid ; but  its  lobes  are  larger,  its  surrounding  cellular  web 
is  finer,  and  its  attachments  are  not  so  firm.  Moreover,  its  duct  has 
much  thinner  coats  than  the  parotid  duct. 

Its  blood-vessels  are  branches  of  the  facial  and  lingual  arferies  and 
veins.  The  nerves  include  those  derived  from  the  small  submaxillary 
ganglion,  as  well  as  branches  from  the  myloid  division  of  the  inferior 
dental  nerve,  and  the  sympathetic. 

The  Sublingual  Gland. 

T)\q  sublingual  gland,  X\\e  smallest  of  the  salivary  glands,  is  of  a 
narrow  oblong  shape,  and  weighs  scarcely  one  drachm.  It  is  situated 
along  the  floor  of  the  mouth,  where  it  forms  a ridge  between  the 
tongue  and  the  gums  of  the  lower  jaw,  covered  only  by  the  mucous 
membrane.  It  reaches  from  the  frasnu'm  linguae,  in  front,  where  it  is 
in  contact  with  the  gland  of  the  opposite  side,  obliquely  backwards 
and  outwards  for  rather  more  than  li  inch.  On  iis  inner  side  it 
rests  on  the  genio-hyoglossus ; beneath,  it  is  supported  by  the  mylo- 
hyoid muscle,  which  is  interposed  between  it  and  the  submaxillary 
gland ; but  it  is  here  in  close  contact  with  the  Whartonian  duct,  with 
the  accompanying  deep  portion  of  the  last-named  gland,  and  also  with 
the  lingual  nerve. 

The  lobules  of  the  sublingual  gland  are  not  so  closely  united  together 
as  those  of  the  other  salivary  glands,  and  the  ducts  from  many  of  them 
open  separately  into  the  mouth,  along  the  ridge  which  indicates  the 
the  position  of  the  gland.  These  ducts,  named  ductus  Riviniani,  are 
from  eight  to  twenty  in  number.  Some  of  them  open  into  the  duct  of 
Wharton.  One,  longer  than  the  rest,  (which  is  occasionally  derived 
in  part  also  from  the  submaxillary  gland,)  runs  along  the  Whartonian 
duct,  and  opens  either  with  it  or  very  near  it ; this  has  been  named 
the  duct  of  Bartholine.  < 

The  sublingual  and  submental  arteries  and  veins  supply  this  small 
gland.  The  nerves  are  numerous,  and  are  derived  from  the  lingual 
branch  of  the  fifth  pair. 

Saliva. — The  saliva  secreted  by  these  glands  is  a clear  limpid  fluid, 
containing  a few  microscopic  granular  corpuscles.  Its  specific  gra- 


440 


THE  PHARYNX. 


vity  is  1-006  to  1-008,  and  it  has  only  about  1 to  parts  of  solid 
matter  in  100.  It  is  always  alkaline  during  the  act  of  mastication; 
but  afterwards  becomes  acid,  and  remains  so  until  the  next  time  of 
taking  food.  Its  chief  ingredients,  besides  water  and  mucus,  are  a 
peculiar  animal  extractive  substance,  named  salivine,  w'ith  some  alka- 
line and  earthy  salts.  It  is  remarkable,  besides,  for  containing  a minute 
proportion  of  sulphocyanide  of  potassium. 

Developing. — In  mammalia,  according  to  Muller  and  Weber,  the  salivary 
glands,  as  shown  in  the  case  of  the  parotid  gland  in  the  embryo  of  the  sheeji, 
(fig.  445.)  first  appear  in  the  form  of  a simple  canal  with  bud-like  processes  lying 
in  a blastema,  and  communicating  with  the  cavity  of  the  mouth.  This  canal 
becomes  more  and  more  ramified  to  form  the  ducts,  whilst  the  blastema  soon 


Fig.  445.  ' Fig.  446. 


Fig.  445.  Early  appearance  of  the  parotid  gland  in  the  embryo  of  the  sheep.  (Muller.) 

Fig.  446.  Lobules  of  the  parotid  gland,  in  the  embryo  of  the  sheep,  in  a more  advanced  condi- 
tion. (Muller.) 


acquires  a lobulated  form  (fig.  446),  corresponding  with  that  of  the  future  gland, 
and  at  last  wholly  disappears,  leaving  the  branched  ducts,  with  their  blood-vessels 
and  connecting  tissues.  The  submaxillary  is  said  to  be  the  first  formed ; then  the 
sublingual  and  the  parotid. 

T H E P H A R Y N X.  * 

The  pharynx  (fig.  444,  p,®)  is  that  part  of  the  alimentary  canal 
which  intervenes  between  the  cavity  of  the  mouth  and  the  oesophagu.s. 
It  is  situated  behind  the  nose,  mouth,  and  larynx,  in  front  of  the  verte- 
bral column,  and  between  the  great  vessels  of  the  neck ; reaching  from 
beneath  the  basilar  process  of  the  occipital  bone  down  to  the  level  of 
the  cricoid  cartilage,  opposite  the  fifth  cervical  vertebra,  where  it  ends 
in  the  oesophagus. 

It  forms  an  oblong  sac,  open  at  the  lower  end,  and  imperfect,  in 
front,  where  it  presents  apertures  leading  into  the  nose,  mouth,  and 
larynx,  but  closed  in  other  directions,  viz.,  above,  behind,  and  at  the 


THE  PHARYNX. 


441 


sides.  The  walls  of  this  sac  consist  of  a fascia  or  layer  of  fibrous 
tissue,  dense  at  its  upper  part,  but  lax  and  weak  below,  surrounded  by 
muscles,  and  lined  by  a mucous  membrane.  Its  upper  end  forms  a 
cul-de-sac  beneath  the  basilar  process,  to  which  and  also  to  the  petrous 
portion  of  the  temporal  bone  it  is  attached  by  a tendinous  expansion, 
which  descends  some  distance  on  its  posterior  and  lateral  surfaces. 
Behind,  it  is  loosely  connected  by  cellular  tissue  to  the  prmvertebral 
fascia  covering  the  bodies  of  the  cervical  vertebrm  and  the  muscles 
which  rest  upon  them.  At  the  side  it  has  similar  connexions,  by  loose 
cellular  tissue,  with  the  styloid  process  and  its  muscles,  and  with 
the  large  vessels  and  nerves  of  the  neck.  In  front,  the  walls  of  the 
pharynx  are  attached  in  succession  to  the  sides  of  the  posterior  nares, 
the  mouth,  and  the  larynx.  Thus,  commencing  above  by  a tendinous 
structure  only,  at  the  petrous  portion  of  the  temporal  bone  and  the 
Eustachian  tube,  its  walls  are  connected  by  means  of  muscle  and 
fibrous  membrane,  first,  with  the  internal  pterygoid  plate,  then  with 
the  pterygo-maxillary  ligament,  and  next  with  the  mylo-hyoid  ridge  of 
the  lower  jaw:  below  this,  again,  they  are  attached  to  the  sides  of  the 
tongue,  to  the  hyoid  bone,  and  stylo-hyoid  ligament;  and  lastly,  to  the 
thyroid  and  cricoid  cartilages. 

The  pharynx  is  about  four  inches  and  a half  in  length,  and  is  some- 
what wider  across  than  it  is  deep  from  before  backwards.  Its  width 
above  is  moderate ; its  widest  part  is  opposite  the  cornua  of  the  hyoid 
bone,  and  below  this  it  rapidly  contracts  towards  its  termination, 
opposite  the  cricoid  cartilage,  which  is  the  narrowest  part. 

The  velum  pendulum  palati  projects  backwards  into  the  pharynx, 
and  during  the  passage  of  the  food  is  applied  to  its  posterior  wall. 
Seven  openings  lead  into  the  cavity  of  the  pharynx;  viz.,  above  the 
velum  the  two  posterior  openings  of  the  nares  (^),  and  at  the  sides  the 
apertures  of  the  Eustachian  tubes  (®) ; below  the  velum  there  is  first 
the  passage  leading  from  the  mouth  (®),  then  the  superior  opening  of 
the  larynx  (^),  and,  lastly,  the  passage  into  the  oesophagus  (®). 

Structure. — The  muscles  of  the  pharynx  are  the  superior,  middle, 
and  inferior  constrictors,  the  stylo-pharyngeus,  and  the  palato-pharyn- 
geus  (vol.  i.  pp.  361 , 366).  At  the  upper  end  of  the  pharynx,  its  structure 
is  strengthened  by  a firm  dense  fascia,  already  referred  to,  named  the 
pharyngeal  aponeurosis,  which  is  attached  above  to  the  basilar  process, 
and,  at  the  sides,  to  the  petrous  portion  of  the  temporal  bones.  It 
diminishes  in  thickness  as  it  descends. 

The  mucous  membi’ane  lining  the  inner  surface  of  the  pharynx  is 
continuous  at  the  several  apertures  with  that  of  the  adjacent  cavities. 
It  varies  somewhat  in  its  character  in  different  parts.  Its  upper  portion 
is  thick  where  it  adheres  to  the  periosteum  of  the  basilar  process,  but 
is  much  thinner  near  the  entrance  of  the  Eustachian  tube  and  the  pos- 
terior nares  : in  this  situation  numerous  glands  are  found  collected  in 
a layer  beneath  the  mucous  membrane.  In  the  part  opposite  the 
tauces,  the  mucous  membrane  exactly  resembles  that  of  the  mouth, 
and  is  provided  with  glands.  Lower  down  it  becomes  paler,  and  at 
the  back  of  the  larynx  it  forms  several  longitudinal  folds  or  plicae. 
According  to  Henle,  the  epithelium  upon  the  upper  portion  of  the 


442 


THE  (ESOPHAGUS. 


pharynx,  as  low  down  as  a horizontal  line  level  with  the  floor  of  the 
nares,  is  columnar  and  ciliated;  but,  below  that  point,  is  squamous  and 
destitute  of  cilia. 

THE  (ESOPHAGUS. 

The  (Esophagus  or  gullet  is  a membranous  tube  leading  from  the 
pharynx  to  the  stomach,  and  forming  the  passage  through  which  the 
food  descends  into  the  latter  organ.  It  commences  at  the  cricoid 
cartilage,  (fig.  444,^)  opposite  the  fifth  cervical  vertebra,  and,  descend- 
ing along  the  front  of  the  spine,  passes  through  the  diaphragm  opposite 
the  ninth  dorsal  vertebra,  and  then  ends  by  opening  into  the  cardiac 
orifice  of  the  stomach  (fig.  448,^). 

The  length  of  the  msophagus  is  about  nine  inches.  The  diameter 
of  its  passage  is  less  than  that  of  any  other  division  of  the  alimentarv 
canal,  its  smallest  part  being  at  the  commencement  behind  the  cricoid 
cartilage;  it  is  also  constricted  in  passing  through  the  diaphragm,  but, 
below  that,  gradually  widens  into  the  stomach  ; [it  very  gradually  in- 
creases in  width  to  the  constrict  ion  at  tli6  passage  through  the  diaphragm.] 
The  oesophagus  isnearly  straight  in  its  direction,  havingonly  two  or  three 
slight  curvatures.  Of  these,  one  corresponds  with  the  antero-posterior 
flexure  of  the  vertebral  column  in  the  neck  and  thorax.  It  also  has  two 
slight  lateral  bendings,  for  though  at  its  commencement  it  is  placed  upon 
the  median  line,  yet,  towards  the  root  of  the  neck,  it  inclines  to  the  left 
side;  from  thence  to  the  fifth  dorsal  vertebra  it  gradually  resumes  its 
position  towards  the  middle  line,  and,  finally,  it  deviates  again  to  the 
left,  at  the  same  time  coming  forward  towards  the  oesophageal  opening 
of  the  diaphragm.  The  oesophagus  is  for  the  most  part  applied  to  the 
anterior  surface  of  the  spine,  being  connected  with  it  and  with  the 
longus  colli  muscle  by  loose  cellular  tissue ; the  thoracic  duct  ascends 
obliquely  from  right  to  left,  between  it  and  the  bodies  of  the  upper 
dorsal  vertebrae,  and  towards  its  lower  extremity  it  is  placed  in  front 
of  the  aorta.  In  the  neck,  the  oesophagus  lies  immediately  behind  the 
trachea;  on  each  side  of  it  is  the  common  carotid  artery,  and  also  a 
part  of  the  thyroid  body,  but,  as  it  inclines  to  the  left  side,  it  is  in  more 
immediate  connexion  with  the  left  carotid;  the  recurrent  laryngeal 
nerves  ascend  between  the  oesophagus  and  trachea.  In  the  thorax, 
the  gullet  is  covered  in  front  by  the  lower  part  of  the  trachea,  by  :he 
commencement  of  the  left  bronchus,  and  by  the  back  of  the  peri- 
cardium. The  aorta,  except  near  the  diaphragm,  where  the  oesophagus 
is  in  front  of  the  vessel,  lies  rather  to  the  left,  and  the  vena  azygos  to 
the  right;  the  pneurnogastric  nerves  descend  in  clo.se  contact  with  its 
sides,  and  form  a plexus  around  it,  the  left  nerve  coming  down  gra- 
dually in  front,  and  the  right  nerve  retiring  behind  it.  Lastly,  the 
oesophagus,  which  is  here  placed  in  the  interval  between  the  two 
pleurae,  receives  a partial  covering  on  each  side  from  those  membranes. 

The  walls  of  the  oesophagus  are  composed  of  three  coats  ; viz.,  an 
external  or  muscular,  a middle  or  cellular,  and  an  internal  or  mucous 
coat. 

The  muscular  coat  consists  of  two  layers  of  fibres,  disposed  in 
different  planes,  and  taking  opposite  directions  ; these  are  an  exter- 
nal longitudinal  layer,  and  an  internal  circular  layer.  This  two- 


THE  ABDOMEN. 


443 


fold  arrangement  of  the  muscular  fibres  of  the  alimentary  canal  pre- 
vails throughout  its  whole  length  ; but  the  two  layers  are  here  much 
thicker,  more  uniformly  disposed,  and  more  evident  than  elsewhere, 
except  quite  at  the  lower  end  of  the  rectum.  The  external  or  longitu- 
dinal fibres  are  disposed  at  the  commencement  of  the  tube  in  three 
fasciculi,  seen  one  in  front,  and  one  on  each  side  of  the  oesophagus. 
The  lateral  bundles  are  blended  above  with  the  inferior  constrictor  of 
the  pharynx;  the  anterior  fasciculus  arises  from  the  back  of  the 
cricoid  cartilage,  at  the  prominent  ridge  between  the  crico-arytenoid 
muscles,  and  then  spreads  out  obliquely  on  each  side  of  the  gullet  as 
it  descends,  and  soon  blends  with  the  lateral  bundles  to  form  a con- 
tinuous layer  around  the  tube.  The  internal  or  circular  fibres,  are 
continuous  above  with  those  of  the  inferior  constrictor  of  the  pharynx. 
The  rings  or  circles  which  they  form  around  the  tube  have  a transverse 
direction  at  the  upper  and  lower  part  of  the  oesophagus,  but  in  the 
intervening  space  are  somewhat  oblique.  At  the  lower  end  of  the 
oesophagus,  both  layers  of  fibres  become  continuous  with  those  of  the 
stomach. 

The  muscular  coat  of  the  upper  end  of  the  oesophagus  is  red,  and 
consists  of  the  striped  muscular  fibres  ; but  lower  down  it  becomes 
paler,  and  is  principally  composed  of  the  plain  muscular  fibres.  A few 
striped  fibres,  however,  are  found  mixed  with  the  others,  and  have 
been  traced  throughout  its  whole  length,  and  even,  it  is  said,  upon  the 
cardiac  end  of  the  stomach.  (Ficinus.) 

The  cellular  coat  is  placed  between  the  muscular  and  mucous  coats, 
and  connects  them  together  but  very  loosely. 

The  mucous  membrane  is  of  firm  texture,  and  is  paler  in  colour  than 
that  of  the  pharynx  or  stomach.  From  its  loose  connexions  its  outer 
surface  is  freely  movable  on  the  muscular  tunic  ; and  when  the  latter 
is  contracted  and  the  oesophagus  is  shut,  as  happens  when  it  is  not 
giving  passage  to  food,  the  sides  of  the  tube  are  in  mutual  contact. 
In  this  state,  the  mucous  membrane  is  thrown  into  longitudinal  folds, 
which  disappear  on  distension  of  the  canal. 

Minute  papillae  are  seen  upon  this  mucous  membrane,  placed  at 
some  distance  from  each  other;  and  the  whole  is  covered  with  a thick 
squamous  epithelium,  w^hich  can  be  traced  as  far  as  the  cardiac  orifice 
of  the  stomach,  where  it  suddenly  changes  its  character,  as  wdll  ,be 
hereafter  noticed. 

The  gullet  is  provided  with  many  small  compound  glands,  named 
(esophageal  glands,  which  are  especially  numerous  at  the  lower  end 
of  the  tube. 

THE  ABDOMINAL  PORTION  OF  THE  DIGESTIVE  ORGANS. 

That  part  of  the  digestive  canal  which  is  found  beneath  the  dia- 
phragm, and  consists  of  the  stomach  and  intestines,  is  situated  within 
the  cavity  of  the  abdomen,  the  extent,  boundaries,  and  regions  of  which 
may  here  be  briefly  explained. 

THE  ABDOMEN. 

The  abdomen  {abdere,  to  conceal)  is  the  largest  cavity  in  the  body, 


444 


REGrONS  OF  ABDOMEN. 


and  is  lined  by  an  extensive  and  complicated  serons  membrane,  named 
the  peritoneum. 

Including  the  cavity  of  the  pelvis,  which  in  fact  constitutes  its  lower 
part,  it  extends  from  the  diaphragm  above  to  the  levatores  ani  muscles 
below;  and  from  the  transversales  muscles  in  front,  to  the  spine,  the 
quadrati  lumborum,  and  iliaci  muscles  behind.  All  of  these  structures, 
excepting  the  diaphragm  and  spine,  are  lined  with  a fibrous  layer  or 
fascia,  which  is  differently  named  according  to  the  parts  to  which  it 
is  attached.  Through  these  several  structures,  which  taken  together 
constitute  the  walls  of  the  abdomen,  several  apertures  exist  for  the 
transmission  of  vessels  or  other  organs  into  and  out  of  the  cavitv. 
Thus,  superiorly,  there  are  three  principal  apertures  in  the  diaphraga', 
for  the  passage  of  the  aorta,  the  vena  cava,  and  the  CEsophagus.  In 
front,  there  is  the  umbilicus,  which  is  pervious  during  foetal  life,  and 
then  transmits  the  umbilical  vessels.  Lower  down,  there  is  an  opening 
on  each  side  for  the  femoral  vessels,  and  a second  on  each  side  for  the 
spermatic  cord  in  the  male,  and  the  round  ligament  of  the  uterus  in 
the  female.  In  the  pelvic  portion  of  this  great  cavity  there  is  an 
opening  for  the  termination  or  outlet  of  the  intestinal  canal,  and 
another  for  that  of  the  genito-urinary  passages.  To  these  may  be 
added  several  smaller  openings  for  blood-vessels  and  nerves. 

The  cavity,  as  above  defined,  contains  the  greater  part  of  the  di- 
gestive organs,  the  urinary 
organs,  and  the  internal 
organs  of  generation.  It  is 
subdivided  into  two  parts;  an 
upper  and  larger  part,  the 
abdomen, 'properly  so  called; 
and  a lower  part,  named  the 
pelvic  cavity.  The  limits 
between  the  abdominal  and 
pelvic  portions  of  the  cavity 
are  marked  by  the  brim  of 
the  pelvis. 

For  the  purpose  of  enabling 
precise  reference  to  be  made 
to  the  situation  and  condition 
of  the  contained  organs,  the 
abdomen  proper  has  been 
artificially  subdivided  into 
certain  regions,  the  bounda- 
ries of  which  are  indicated 
by  lines  dravvn  upon  the  sur- 
face of  the  body.  Thus,  two 
transverse  lines  drawn  round 

Surface  of  the  abdomen,  willi  lines  (1, 
2,  3,  4)  drawn  upon  it,  marking  off  its 
artificial  subdivisions  into  regions.  6, 
5.  Kight  and  loft  hypochondriac.  6.  Epi- 
gastric region.  7.  Umbilical.  8,  8.  The  two  lumbar.  9.  Hypogastric.  10,  10.  The  right  and 
left  iliac  regions.  11.  Regio  pubis. 


DIVISIONS  OF  ALIMENTARY  CANAL. 


445 


the  body  divide  it  into  three  zones ; viz.,  an  upper,  a middle,  and  a 
lower.  One  of  these  transverse  lines,  commencing  at  the  most  promi- 
nent point  of  the  costal  cartilages  at  one  side,  is  drawn  across  to  the 
corresponding  point  on  the  opposite  side,  and  thence  round  the  back  to 
the  place  at  which  it  began.  The  other  line,  proceeding  from  the 
crest  of  the  ilium  at  one  side,  extends  to  that  of  the  other,  and  so  round 
the  body,  as  in  the  former  instance.  These  zones  are  further  subdi- 
vided into  three  parts  by  means  of  two.  perpendicular  lines,  drawn 
from  the  cartilage  of  the  eighth  rib,  at  each  side,  down  to  the  centre 
of  Poupart’s  ligament. 

The  upper  zone  is  thus  marked  off  into  the  right  and  left  hypochon- 
driac (ij-ro,  under ; %ov(5|og,  the  cartilage)  regions  (fig.  447,  * *),  and  the 
epigastric  (s-jti,  upon;  yaffTTip,  the  stomach)  region  (*),  which  is  some- 
times called  scrobiculus  cordis.  p. 

The  middle  zoneis  divided  intothe 
umbilical  region  in  the  centre  (®), 
and  the  right  and  left  lumbar 
regions  (®  ■’*) ; and  the  inferior 
zone  into  the  hypogastric  or  pubic 
region  (®),  in  the  centre,  and  the 
iliac  region  at  each  side  (®®). 

Now  the  subdiaphragmatic  or 
abdominal  portion  of  the  ali- 
mentary canal,  and  its  several 
accessory  viscera,  occupy  nearly 
the  whole  of  the  cavity  of  the 
abdomen, — the  urinary  organs, 
and  some  part  of  the  organs  of 
generation  taking  up  but  a very 
limited  space  within  it. 

This  part  of  the  digestive  tube 
is  subdivided  into  the  stomach, 

(fig.  448,^),  the  small  intestine,^ 
and  the  great  intestine  (^^^),  dis- 
tinctions which  are  founded  on 
evident  differences  of  form  and 
structure.  The  small  intestine  is 
further  distinguished  by  anato- 
mists into  three  parts,  named  the 
duodenum  (®),  the  jejunum  (j), 
and  the  ileum  (®).  The  large 
intestine,  also,  is  distinguished 
into  the  caecum  (®),  the  co/on  ^*), 
and  the  rectum  (“).  Moreover, 
the  colon  itself  is  named,  in  its 
different  parts,  the  ascending  (’’), 
transverse  (^),  and  descending 

Fig.  448.  Diagram  of  the  stomach  and  intestines,  to  show  their  course.  1.  Stomach.  2.  (Eso- 
phagus. 3.  Left,  and  4,  Right  end  of  stomach.  5,  6.  Duodenum.  7.  Convolutions  of  jejunum. 
8.  Those  of  ileum.  9.  Coacum.  10.  Vermiform  appendix.  11.  Ascending.  12.  Transverse; 
and  13.  Descending  colon.  14.  Commencement  of  sigmoid  flexure.  15.  Rectum. 

VOL.  II.  38 


446 


THE  STOMACH. 


colon ; and  at  its  lower  part,  presents  a remarkable  bend,  called  the 
sigmoid Jlexure  (*“). 

On  opening  the  abdomen,  from  the  front,  these  several  parts,  and 
also  the  viscera  appended  to  them,  are  seen  to  be  more  or  less  covered 
by  the  general  lining  membrane  of  the  cavity,  named  the  peritoneum  ^ 
and  are  found  to  be  attached  to  its  posterior  and  upper  walls,  by 
means  of  folds  or  duplicatures  of  that  membrane,  which  include  the 
blood-vessels,  nerves,  and  lymphatics  belonging  to  each  organ. 

A general  idea  of  the  position  and  arrangement  of  the  abdominal 
viscera  may  be  obtained  by  referring  them  to  the  transverse  colon. 
This  portion  of  the  large  intestine  crosses  through  the  abdomen  from 
right  to  left,  immediately  behind  the  anterior  wall,  a little  above  the 
umbilicus.  Together  with  the  peritoneal  fold,  called  the  transverse 
mesocolon,  by  which  it  is  attached  behind,  the  transverse  colon  divides 
the  abdominal  cavity  into  two  parts,  one  being  above  and  the  other 
below  it. 

Above  it,  are  found  the  liver,  with  its  excretory  apparatus,  which 
occupies  the  right  hypochondrium,  a part  of  the  epigastrium,  and  ex- 
tends a short  way  into  the  left  hypochondrium;  the  stomach,  which  lies 
in  the  epigastric  and  left  hypochondriac  regions;  the  spleen,  which  is 
closely  applied  to  the  left  end  of  the  stomach  ; and,  lastly,  the  com- 
mencement of  the  duodenum,  which  is  continuous  with  the  right  end 
of  the  stomach. 

Below  the  transverse  colon,  and  covered  by  a process  of  the  peri- 
toneum, containing  fat,  and  called  the  great  omentum,  are  found  the 
convolutions  of  the  jejunum  and  ileum,  attached  by  the  mesentery. 
These  convolutions  occupy  the  umbilical  and  hypogastric  regions, 
and  are  surrounded  by  the  large  intestine,  which  occupies  the  iliac 
and  lumbar  regions  on  each  side,  and  crosses  the  upper  part  of  the 
umbilical  region,  as  already  mentioned.  On  lifting  up  the  transverse 
colon,  with  its  mesocolon,  the  termination  of  the  duodenum  is  seen 
passing  under  it;  and,  placed  across  the  spine  at  the  root  of  the  meso- 
colon, and  above  the  last  portion  of  the  duodenum,  is  found  the  pan- 
creas. The  rectum,  or  lower  part  of  the  large  intestine,  passes  down 
into  the  pelvic  cavity. 

On  removing  the  digestive  organs  from  the  abdomen,  the  kidneys, 
supra-renal  capsules,  and  ureters,  the  great  blood-vessels,  lymphatics 
and  nerves,  are  found  lying  quite  at  the  back  of  that  cavity.  The 
bladder  when  full,  and  the  uterus  in  its  gravid  state,  project  upwards 
into  the  abdomen,  and  displace  the  small  intestine. 

THE  STOMACH. 

The  stomach  (fig.  448,^;  yarfTiif)  is  that  dilated  portion  of  the  ali- 
mentary canal  which  intervenes  between  the  oesophagus  and  the  duo- 
denum, and  within  which  the  food  is  to  be  retained  to  be  acted  on  by 
the  gastric  juice,  and  to  be  converted  into  chyme. 

This  organ  is  seated  in  the  left  hypochondriac  and  the  epigastric 
regions,  and  in  a part  also  of  the  right  hypochondrium.  It  is  placed 
across  behihd  the  anterior  wall  of  the  abdomen,  beneath  the  liver  and 
diaphragm,  and  above  the  transverse  colon. 


THE  STOMACH. 


447 


Fig.  449, 


The  stomach,  when  distended,  has  the  shape  of  an  irregular  cone 
having  a rounded  base  and  being  curved  upon  itself.  The  left  extre- 
mity 0 is  the  larger,  and  is  named  the  great  or  splenic  end  of  the 
stomach.  The  right  or  small  end  (^)  is  also  named  the  pyloric  extre- 
mity. Of  its  two  orifices,  the  one  by  which  food  enters  from  the  oeso- 
phagus is  named  the  cardiac  orifice  (fig.  449,  o),  the  other,  by  which 
the  stomach  communicates  with  the  duodenum,  and  which  is  placed 
on  a little  lower  level,  and  more  forwards,  is  the  pyloric  orifice  {q). 

The  oesophagus  terminates  in  the  stomach  two  or  three  inches  from 
the  great  extremity,  which  projects  beyond  that  tube  to  the  left,  and 
is  named  the  great  cul-de-sac  or  fundus  (c). 

Between  the  cardiac  and  the  pyloric  orifices,  the  outline  of  the  sto- 
mach is  curved  along  its  upper  and  lower  borders.  The  upper  border, 
about  three  inches  in  length,  is  concave,  and  is  named  the  lesser  cur- 
vature (b) ; while  the  lower  border,  which  is  much  longer,  and,  except 
towards  the  pylorus,  convex,  forms  the  greater  curvature  (a).  These 
two  borders  or  curvatures  constitute  the  limits  betw'een  the  anterior 
and  the  posterior  surfaces  of  the  organ. 

Towards  the  pylorus  {q),  the  small  end  of  the  stomach  describes  a 
double  bend,  opposite  to  the  first  turn  of  which  is  a prominence  or 
bulging,  sometimes  named  the  small  cul-de-sac  or  antrum  pylori  (d). 

dimensions. — These  vary  greatly  according  to  the  state  of  dis- 
tension of  the  organ.  When 
moderately  filled,  its  length  is 
about  ten  or  twelve  inches ; 
and  its  diameter,  at  the  widest 
part,  from  four  inches  to  four 
inches  and  a half.  Accord- 
ing to  Clendinhing,  it  weighs, 
when  freed  from  other  parts, 
about  four  ounces  and  a half 
in  the  male,  and  somewhat 
less  in  the  female. 

Connexions. — The  stomach 
is  in  contact  with  many  sur- 
rounding parts,  to  several  of 
which  it  is  attached  in  diffe- 
rent ways. 

Its  anterior  and  posterior  surfaces  are  free,  smooth,  and  covered 
with  peritoneum.  The  anterior  surface,  which  is  directed  slightly 
upwards  as  well  as  forwards,  is  in  contact  above  with  the  diaphragm 
and  the  under  surface  of  the  liver,  and  lower  down  with  the  abdominal 
parietes  opposite  to  the  epigastric  region,  w'hich  is  hence  named  the 
pit  of  the  stomach.  The  posterior  surface  is  turned  downwards  and 
backwards,  and  rests  upon  the  transverse  meso-colon,  and  further 
back,  upon  the  pancreas  and  great  vessels  of  the  abdomen. 

At  its  cardiac  orifice  it  is  continuous  with  the  cesophagus,  and  is, 
therefore,  fixed  to  the  oesophageal  opening  in  the  diaphragm,  being 
also  connected  with  that  muscle  by  a reflection  of  the  peritoneum, 
sometimes  named  the  gastro-phrenic  ligament.  This  is,  therefore,  the 


Dingram  outline  of  stomach. — a.  Great  curvature,  b. 
Lesser  curvature,  c.  Left  end,  great  cul-de-sac  or 
fundus,  d.  Small  cul-de-.>-ac  or  antrum  pylori,  o. 
(Esophageal  orifice  or  cardia.  p.  Duodenal  orifice  or 
pyloruST 


448 


THE  STOMACH. 


most  fixed  part  of  the  stomach,  and  is  placed  higher,  and  at  the  same 
time  further  back,  than  any  other  part  of  the  organ.  The  pyloric  ex- 
tremity, situated  lower  down,  nearer  to  the  surface,  and  having  greater 
freedom  of  motion,  is  continuous  with  the  duodenum.  It  is  covered 
by  the  concave  surface  of  the  liver,  and,  in  some  cases,  touches  the 
neck  of  the  gall-bladder.  The  lesser  curvature,  which  is  turned  up- 
wards and  backwards,  is  connected  by  means  of  a fold  of  the  perito- 
neum, named  the  lesser  or  gastro-hepatic  omentum,  with  the  under 
surface  of  the  liver.  From  the  greater  curvature  of  the  stomach  pro- 
ceeds another  double  layer  of  peritoneum,  loaded  with  fat,  which  is 
called  the  great  or  gastro-colic  omentum.  The  duplicature  of  peritc-- 
neum  forming  the  gastro-hepatic  omentum,  having  reached  the  lessor 
curvature  of  the  stomach,  separates  into  its  two  layers,  of  which  one 
passes  over  the  anterior  surface,  and  the  other  upon  the  posterior  sur- 
face of  the  organ,  as  far  as  to  its  greater  curvature:  here  they  again 
become  applied  to  one  another,  and,  leaving  the  stomach,  pass  down 
in  front  of  the  small  intestine,  and  form  the  great  omentum,  which, 
again  turning  upwards,  becomes  attached  to  the  transverse  colon. 
The  blood-vessels  and  lymphatics  of  the  stomach  pass  within  these 
duplicatures  of  the  peritoneum,  and  reach  the  organ  along  its  two 
curvatures.  Lastly,  the  great  cul-de-sac  is  in  contact  partly  with  the 
diaphragm,  but  chiefly  with  the  concave  surface  of  the  spleen,  with 
which  it  is  connected  by  means  of  a fold  of  peritoneum,  named  the 
gastro-splenic  omentum,  and  by  its  contained  vessels. 

When  the  stomach  is  distended,  its  position  and  direction  are 
changed.  The  oesophageal  end  being  fixed  to  the  back  part  of  the 
diaphragm  cannot  alter  much,  but  the  duodenal  extremity  has  more 
liberty  of  motion.  The  lesser  curvature  is,  also,  tolerably  well  fixed 
to  the  liver  by  the  small  omentum,  while  the  great  curvature  is  the 
most  movable  part:  accordingly,  when  the  stomach  is  distended,  this 
curvature  is  elevated  and  at  the  same  time  carried  forwards,  whilst 
the  anterior  surface  is  turned  upw'ards  and  the  posterior  surface  down- 
wards. 

Structure. — The  walls  of  the  stomach  consist  of  four  distinct  coats, 
held  together  by  fine  cellular  tissue.  They  are  named,  in  order  from 
within  outw’ards,  the  serous,  muscular,  cellular,  and  mucous  coats. 
By  some  the  cellular  coat  is  not  reckoned  as  a separate  tunic.  Taking 
all  the  coats  together,  the  walls  of  the  stomach  are  thinner  than  those 
of  the  oesophagus,  but  rather  thicker  than  those  of  the  intestines  gene- 
rally. They  are  thickest  at  the  pyloric  end,  and  thinnest  in  the  great 
cul-de-sac. 

The  external  or  serous  coat,  derived  from  the  peritoneum,  is  a thin, 
smooth,  transparent,  and  elastic  membrane,  which  covers  the  entire 
viscus,  excepting  along  its  tw’o  curvatures,  from  which,  as  already 
mentioned,  it  is  reflected  so  as  to  form  the  small  and  great  omenta. 
Along  the  place  of  this  reflection,  between  the  borders  of  the  stomach 
and  the  two  layers  of  the  peritoneum,  is  a three-sided  space,  occupied 
by  loose  cellular  tissue,  and  containing  the  larger  blood-vessels  and 
lymphatics  of  the  organ,  which,  in  this  w’ay,  reach  and  run  along  the 
two  curvatures.  The  existence  of  this  space,  and  the  loose  nature  of 


STRUCTURE  OF  THE  STOMACH. 


449 


the  attachment  of  the  peritoneal  tunic  in  its  neighbourhood,  must  faci- 
litate the  alternate  distension  and  collapse  of  the  stomach.  In  other 
situations,  the  serous  coat  adheres  firmly  to  the  muscular  coat. 

The  second,  or  muscular  coat  is  composed  of  three  sets  of  fibres, 
named  from  their  direction,  the  longitudinal,  the  circular,  and  the 
oblique  fibres,  which  form  three  layers. 

The  first  or  outermost  layer  consists  of  the  longitudinal  fibres, 
which  are,  in  fact,  a continuation  of  those  of  the  oesophagus.  They 
spread  out  in  a radiating  manner  from  the  cardiac  orifice,  for  which 
reason  they  are  sometimes  called  the  stellate  fibres,  and  are  found  in 
greatest  abundance  along  the  curvatures,  especially  on  the  lesser  one. 
On  the  anterior  and  posterior  surfaces  they  are  very  thinly  scattered, 
or  are  not  to  be  found  at  all.  Towards  the  pylorus  they  are  arranged 
more  closely  together  and  form  a thicker  uniform  layer,  which  be- 
comes continuous  with  the  longitudinal  fibres  of  the  duodenum. 

The  second  set  are  the  circular  fibres,  which  form  a complete  layer 
over  the  whole  extent  of  the  stomach.  They  commence  by  small  and 
thinly  scattered  rings  at  the  left  extremity  of  the  great  cul-de-sac, 
describe  larger  and  larger  circles  as  they  surround  the  body  of  the 
stomach,  and  towards  the  pyloric  end  again  form  smaller  rings  and  at 
the  same  time  become  much  thicker  and  stronger  than  at  any  other 
point.  At  the  pylorus  itself,  they  are  gathered  into  an  annular  bundle, 
which  projects  inw'ards  into  the  cavity  and  forms,  together  w’ith  a 
covering  of  mucous  membrane,  ihe  pyloric  sphincter. 

The  innermost  muscular  layer  is  incomplete,  and  consists  of  the 
oblique  fibres.  These  oblique  fibres  are  continuous  with  the  circular 
fibres  of  the  gullet ; they  embrace  the  cardiac  orifice  on  the  left, 
where  they  form  a considerable  stratum,'and  from  that  point  descend 
obliquely  upon  the  anterior  and  posterior  surfaces  of  the  stomach, 
where  they  spread  out  from  one  another  and  gradually  disappear. 
They  are  best  seen  from  the  inside  of  the  stomach,  after  removing  the 
mucous  membrane. 

The  muscular  fibres  are  of  a pale  reddish  colour.  They  belong  to 
the  class  of  plain  fibres,  but  amongst  them,  however,  Ficinus  and 
Valentin  have  found  some  connected  with  the  longitudinal  layer  which 
are  indistinctly  striated. 

The  cellular,  or  fibrous  coat  of  the  stomach  is  a tolerably  distinct 
layer  placed  between  the  muscular  and  mucous  coats,  and  connected 
with  both.  It  has  algo  been  named  from  its  position  the  submucous 
coat,  and  from  its  white  colour,  \\\e  nervous  tunic;  but  it  consists 
essentially  of  a dense  filamentous  areolar  tissue.  It  serves  to  support 
the  mucous  coat,  and  also  forms  a layer  in  which  the  blood-vessels 
ramify  before  they  enter  that  membrane  : hence  it  is  sometimes  called 
the  vascular  coat.  This  is  not  the  only  cellular  layer  in  the  w’alls  of 
the  stomach,  for  one  may'  be  demonstrated  between  the  muscular  and 
serous  coats,  serving  to  connect  them  together,  but  it  is  very  fine  and 
is  not  described  as  a separate  tunic. 

The  internal  or  mucous  coat  is  a smooth,  soft,  rather  thick  and 
pulpy  membrane,  w'hich  has  generally  a palish  pink  hue  owing  to  the 
blood  in  its  capillary  vessels,  but  which,  after  it  has  been  well  washed, 

38* 


450 


MUCOUS  COAT  OF  STOMACH. 


is  of  a grayish  white  or  pale  straw  colour.  In  some  cases,  however, 
it  presents  this  pale  aspect  without  any  previous  washing.  In  infancy 
the  vascular  redness  is  more  ix.arked,  the  surface  having  then  a rosy 
hue,  but  it  becomes  paler  in  childhood,  and  in  aged  persons  is  often  of 
an  ash-gray  colour.  During  digestion  its  vessels  become  congested, 
and  when  examined  in  that  condition  it  is  always  much  darker  than 
usual. 

After  death  a few  hours  will  often  suffice  to  change  its  colour  to  a dirty  brown 
tint,  mottled  and  streaked  in  some  cases  with  dull  red  lines,  corresponding  with 
the  course  of  the  veins.  This  alteration  is  owing  to  the  exudation  of  the  colour- 
ing matter  of  the  blood,  and  is  especially  met  with  in  old  subjects,  in  whom  the 
mucous  membrane  is  always  thin.  In  acute  inflammation,  or  after  the  introduc- 
tion of  irritating  substances  or  of  strong  acrid  poisons,  it  becomes  of  a bright  red, 
either  all  over  or  in  spots,  patches  or  streaks  of  variable  sizes.  Corrosive  poi- 
sons, the  gastric  juice,  and  sometimes  regurgitating  bile,  may  stain  it  variously 
black,  brown,  yellow,  or  green;  and  the  effect  of  chronic  inflammation  is  to  leave 
the  membrane  of  a slate-gray  colour. 

Independently  of  all  these  modifying  circumstances  connected  with  the  sto- 
mach itself,  as  was  pointed  out  by  Dr.  Yelloly  and  others,  the  colour  of  the 
gastric  mucous  surface  is  liable  to  be  influenced  by  causes  of  a more  general 
nature.  Thus,  it  has  been  found  that  in  cases  of  obstructed  venous  circulation, 
as  when  death  occurs  from  hanging  or  from  drowning,  and  also  in  certain  diseases 
of  the  heart,  the  internal  surface  of  the  stomach  is  reddened  to  a greater  or  less 
extent ; but  the  amount  of  vascularity  may  vary  from  circumstances  which  are 
not  well  understood,  and  may  be  found  greatly  increased  in  cases  in  which  none 
of  those  already  named  exist. 

The  gastric  mucous  membrane  is  thickest  in  the  pyloric  portion  of 
the  stomach,  and  thinnest  in  the  great  cul-de-sac.  It  always  becomes 
thinner  in  old  age. 

The  outer  or  adherent  surface  of  the  mucous  membrane  is  connected 
with  the  muscular  coat  so  loosely  as  to  be  movable  upon  it.  In  con- 
sequence of  this,  and  of  the  great  extent  and  want  of  elasticity  of  the 
mucous  membrane  as  compared  with  the  other  coats,  the  internal 
surface  of  the  sfomach,  when  that  organ  is  in  a contracted  state,  is 
thrown  into  numerous  convoluted  ridges,  rugcB,  which  are  produced 
by  the  puckering  of  the  mucous,  accompanied  by  the  cellular  coat, 
and  are  entirely  obliterated  by  distension  of  the  stomach.  These  folds 
of  the  mucous  coat  are  most  evident  along  the  great  curvature,  and 
have  a general  longitudinal  direction. 

On  examining  the  gastric  mucous  membrane  closely  with  the  aid  of 
a simple  lens,  it  is  seen  to  be  marked  throughout,  but  more  plainly 
towards  the  pyloric  extremity,  with  little  depressions  or  cells  named 
alveoli,  (fig.  450,)  which  have  a polygonal  figure,  and  vary  from 
about  to  T^j^th  of  an  inch  across,  being  larger  and  more  oblong 
near  the  pylorus. 

Towards  the  pyloric  region  of  the  stomach,  where  the  mucous 
membrane  is  thicker  than  elsewhere,  the  margins  of  these  alveoli  are 
elevated  into  pointed  processes,  which  may  be  compared  to  rudimen- 
tary villi,  the  perfect  forms  of  those  appendages  existing  only  in  the 
small  intestine,  and  making  their  appearance  in  the  duodenum,  imme- 
diately beyond  the  pylorus. 

At  the  bottom  of  the  alveoli  or  pits  above  described,  and  also  in  the 
intervals  between  them,  are  seen  small  round  apertures,  which  are  the 


MUCOUS  COAT  OF  STOMACH. 


451 


mouths  of  minute  tubes,  placed  perpendicularly  to  the  surface,  closed 
at  their  attached  or  deep  extremity,  which  rests  on  the  submucous 
cellular  tissue,  and  opening  at  the  other  on  the  inner  surface  of  the 
stomach.  On  making  a vertical  section  of  the  membrane,  and  sub- 
mitting it  to  the  microscope,  it  is  seen  to  consist  almost  entirely  of 
these  small  tuhuli,  arranged  close  to,  and  parallel  with  each  other 
(fig.  451).  Their  diameter  varies  from  to  of  inch,  and 
their  length  from  g^th  to  j-'oth  of  an  inch.  At  the  cardiac  end  of  tfie 
stomach,  where  the  membrane  is  thinnest,  they  are  shorter  and  are 
simply  tubular ; but,  in  approaching  the  pyloric  portion,  they  gradu- 
ally become  longer  and  assume  a more  complicated  form,  for  though 
quite  straight  near  their  orifices,  they  are  convoluted  or  irregularly 
sacculated  towards  their  deep  or  closed  extremity.  These  characters 
are  most  perfect  near  the  pylorus.  Sometimes  two  or  more  of  these 
compound  tubuli  unite,  and  open  by  a single  orifice.  They  exist  at 
all  parts  of  the  stomach,  even  where  the  alveoli  are  indistinct  or  ab- 
sent; they  contain  a colourless  fluid,  with  granular  matter,  and  appear 
to  be  the  secreting  organs  of  the  gastric  juice.  They  are  formed  of  a 
simple  homogeneous  membrane,  lined  by  a columnar  epitltelium  (fig. 
452),  which  becomes  spheroidal  towards  their  closed  extremity. 

Fig.  452. 


Fig.  451. 


Fig.  450.  View  of  the  cells  of  the  raucous  raembrane  of  the  human  stomach,  magnified  thirty- 
two  diameters.  After  Dr.  Sprott  Boyd.  The  hexagonal  cells  with  their  intermediate  elevated 
margins,  and  the  mouths  of  the  tubuli  at  the  bottom  of  each,  are  shown. 

Fig.  451.  Section  of  the  mucous  membrane  of  the  stomach  of  the  pig,  made  perpendicular  to 
the  surface, showing  the  tubuli;  the  blood-vessels  in  the  submucous  cellular  tissue  are  injected. 
Magnified  about  twenty  diameters.  (Boyd.) 

Fig.  453.  One  of  the  tubuli  from  the  stomach  of  the  pig.  It  is  cut  obliquely,  and  shows  the 
columnar  epithelium  with  which  it  is  lined;  at  the  lower  part  the  outer  or  attached  ends  of  the 
columnar  particles  are  seen,  with  their  contained  nucleus.  After  Wasmann. 

In  some  cases,  much  more  evidently  than  in  others,  the  surface  of 
the  mucous  membrane  in  the  pyloric  portion  of  the  stomach,  and  also 
along  the  adjacent  part  of  the  great  curvature,  presents  to  the  naked 
eye  numerous  rounded  and  whitish  eminences,  surrounded  by  slight 
circular  furrows.  Cruveilhier  suggests  that  the  term  granular  or 
glandular  might  be  applied  to  stomachs  having  this  appearance.  The 
eminences  in  question  have  been  carefully  examined  by  Bischoff,  who 


Fig.  450. 


452 


THE  PYLORUS. 


states  that  they  have  no  peculiar  structure,  and  are  merely  thicker 
portions  of  the  mucous  membrane.  But  although  a finely  mammillated 
or  convoluted  appearance  (sornewliat  like  the  surface  of  the  brain  re- 
presented in  miniature)  of  the  mucous  membrane  of  the  stomach  may 
be  caused  by  simple  elevations  which  are  not  glandular,  this  membrane 
is  nevertheless  provided  with  lenticular  follicles,  which  when  unusually 
prominent  give  rise  to  an  appearance  similar  to  that  above  described. 
These  follicles  are  marked  with  a depression  in  the  centre,  and  are 
found  in  greater  or  less  numbers  all  over  the  stomach,  but  are  most 
numerous  towards  the  pylorus.  They  are  best  seen  in  the  stomachs 
of  infants  and  children.  Around  the  cardiac  orifice  they  assume  the 
character  of  multilocular  crypts. 

The  mucous  membrane  of  the  stomach  is  covered  with  an  epithe- 
lium, so  thin,  however,  that  its  existence  was  long  doubted  by  anato- 
mists, who  conceived  that  the  epithelial  layer  ceased  at  the  festooned 
border  of  the  oesophageal  mucous  membrane.  A distinct  epithelium 
exists  all  over  the  .stomach,  covering  the  margins  and  floors  of  the 
alveoli,  and  lining  the  tubuli  also  (fig.  452).  It  for  the  most  part 
belongs  to  the  columnar  variety,  alternating  in  some  parts  with  the 
squamous,  which  is  composed  of  very  minute  polygonal  scales. 

Vessels  and  /lerues.— The  stomach  is  a highly  vascular  organ.  Its 
arterial  branches,  derived  from  all  three  divisions  of  the  coeliac  axis, 
reach  the  stomach  between  the  folds  of  the  peritoneum,  and  form,  by 
anastomosing  together,  two  principal  arterial  arches,  which  are  placed 
along  its  two  curvatures.  That  situated  along  the  lesser  curvature  is 
formed  by  the  union  of  the  coronary  artery  and  the  pyloric  branch  of 
the  hepatic  artery;  while  the  one  found  at  the  great  curvature  is 
formed  by  the  junction  of  the  right  gastro-epiploic  branch  from 
the  hepatic  artery,  and  the  left  gastro-epiploic  from  the  splenic. 
Besides  these,  the  great  cul-de-sac  receives  the  vasa  brevia,  which 
are  branches  of  the  splenic  artery.  After  ramifying  betw'een  the 
several  coats  and  supplying  them  with  blood,  and  especially  after 
dividing  into  very  small  vessels  on  the  submucous  cellular  tunic,  the 
ultimate  arterial  branches  enter  the  mucous  membrane,  and  ramifying 
freely,  pass  to  its  surface  between  the  tubuli,  and  end  in  a capillary 
network  upon  the  hexagonal  borders  of  the  alveoli.  The  veins,  cor- 
responding with  the  arteries,  return  the  residual  blood  into  the  splenic 
and  superior  mesenteric  veins,  and  also  directly  into  the  vena  portae. 

The  absorbents  are  very  numerous ; they  form  a deep  and  a super- 
ficial set,  and  pass  through  lymphatic  glands  found  along  the  two 
curvatures  of  the  stomach. 

The  nerves,  which  are  large,  consist  of  the  terminal  branches  of  the 
two  pneumogastric  nerves,  belonging  to  the  cerebro-spinal  system,  and 
of  offsets  from  the  sympathetic  system,  derived  from  the  solar  plexus. 
The  left  pneumogastric  nerve  descends  on  the  front,  and  the  right  upon 
the  back  of  the  stomach. 

The  Pylorus. — While  there  is  no  special  apparatus  at  the  cardiac 
orifice  of  the  stomach  for  closing  the  passage  from  the  oesophagus,  the 
opening  at  the  pyloric  end,  leading  from  the  stomach  into  the  duode- 
num, is  provided  with  a sphincter  muscle.  On  looking  into  the  pyloric 
end  of  the  stomach,  the  mucous  membrane  is  seen  projecting  in  the 


THE  SMALL  INTESTINE. 


453 


form  of  a circular  fold,  called  the  pylorus,  leaving  a correspondingly 
narrow  opening.  Within  this  fold  are  circular  muscular  fibres,  be- 
longing to  the  general  system  of  circular  fibres  of  the  alimentary 
canal,  which  are  here  accumulated  in  the  form  of  a strong  band, 
whilst  the  longitudinal  muscular  fibres  and  the  peritoneal  coat  pass 
over  the  pyloric  fold  to  the  duodenum,  and  do  not  enter  into  its  for- 
mation. Externally  the  pylorus  may  be  easily  felt,  like  a thickened 
ring,  at  the  right  end  of  the  stomach.  Intex’nally  its  opening  is  usually 
circular,  and  less  than  half  an  inch  across,  so  that  it  is  the  narrowest 
part  of  the  whole  alimentary  canal.  Occasionally  the  orifice  is  oval, 
and  it  is  often  placed  a little  to  one  side.  Sometimes  the  circular  rim 
is  imperfect,  and  there  are  found  instead  two  crescentic  folds,  placed 
one  above  and  the  other  below  the  passage  (Huschke);  and,  lastly, 
there  is  occasionally  but  one  such  crescentic  fold. 

THE  SMALL  INTESTINE. 

The  remaining  part  of  the  alimentary  tube,  extending  from  the 
stomach  to  the  anus,  constitutes  the  intestines,  or  the  intestinal  canal. 
It  is  divided  into  two  portions,  one  named  the  small  intestine,  in  which 
the  bile  and  the  pancreatic  juice  are  added  to  the  digestive  mass,  and 
the  fluid  chyle  is  formed  and  fitted  for  absorption  by  ^the  lacteal  ves- 
sels; and  the  other  called  the  large  intestine,  through  which  the  re- 
sidual and  excrementitious  matter  is  conveyed  out  of  the  body. 

The  small  intestine  (intestinum  tenue ; fig.  448,  ®,  »,)  reaches  from 

the  pylorus  to  the  ileo-colic  valve,  at  which  it  opens  into  the  large 
intestine.  It  consists  of  a long  tube,  having  a convoluted  course, 
measuring  on  ?m  average  about  twenty  feet  in  the  healthy  adult,  and 
becoming  gradually,  though  slightly,  narrower  from  its  upper  to  its 
lower  end.  Its  numerous  convolutions  occupy  the  middle  regions  of 
the  abdomen,  and  are  surrounded  by  the  large  intestine.  They  are 
connected  with  the  back  of  the  abdorhinal  cavity,  and  are  held  in  their 
position  by  a covering  and  fold  of  the  peritoneum,  named  the  me- 
sentery, and  by  numerous  blood-vessels  and  nerves. 

The  small  intestine  is  arbitrarily  divided  into  three  portions,  which 
have  different  names;  the  first  eight  or  ten  inches  immediately  suc- 
ceeding to  the  stomach,  and  comprehending  the  widest  and  most  fixed 
part  of  the  tube,  being  called  the  duodenum  (®),  the  upper  two-fifths  of 
the  remainder  being  named  the  jejunum  E),  and  the  lower  three-fifths 
the  ileum  (®).  There  are  no  distinct  lines  of  demarcation  between 
these  three  parts,  but  there  are  certain  peculiarities  of  connexion  and 
certain  differences  of  internal  structure  to  be  observed  in  comparing 
the  upper  and  lower  ends  of  the  entire  tube,  which  will  be  pointed  out 
after  it  has  been  described  as  a whole. 

Structure. — The  walls  of  the  small  intestine  are  composed  of  four 
coats,  resembling  those  of  the  stomach  in  their  nature  and  relative 
position,  and  named  accordingly  the  serous,  muscular,  cellular,  and 
mucous  coats. 

The  external  or  serous  coat  is  a thin  transparent  tunic,  smooth  on 
its  outer  surface,  and  attached  firmly  at  its  inner  side  by  means  of 
cellular  tissue  to  the  succeeding  or  muscular  coat.  Derived  from  the 


454 


COATS  OF  SMALL  INTESTINE. 


peritoneum,  this  serous  coat  almost  entirely  surrounds  the  intestinal 
tube,  leaving  only  a narrow  interval  along  one  border  of  the  intestine, 
where  it  is  reflected  frtim  it  and  becomes  continuous  with  the  two 
layers  of  the  peritoneal  duplicature  named  the  mesentery.  The  line 
at  which  this  reflection  takes  place  is  named  the  attached  or  mesenteric 
border  of  the  intestine.  The  opposite  border  and  sides  of  the  tube, 
which  are  covered  by  the  peritoneum,  are  quite  free  and  movable 
upon  the  adjacent  parts. 

The  mesentery  itself,  which  is  some  inches  broad,  is  connected  at 
its  posterior  margin  with  the  back  of  the  abdomen,  so  that  it  serves  to 
support  the  intestine,  and  at  the  same  time  leaves  it  capable  of  a con- 
siderable degree  of  movement.  The  blood-vessels,  lacteals,  and 
nerves  are  also  conveyed  along  the  mesentery,  and  reach  the  intestine 
at  its  attach'ed  border,  where  for  a small  space  the  serous  coal  is 
wanting. 

The  upper  part  of  the  small  intestine,  named  the  duodenum,  is 
but  partially  covered  by  the  peritoneum,  which  there  forms  no  me- 
sentery. 

The  muscular  coat  consists  of  two  layers  of  fibres ; an  outer  longi- 
tudinal, and  an  inner  or  circular  set.  The  longitudinal  fibres  are  but 
very  thinly  scattered,  and  are  most  obvious  along  the  free  border  of 
the  intestine.  The  circular  layer  is  much  thicker  and  more  distinct; 
its  fibres  are  placed  closely  together,  and  run  in  a circular  direction 
around  the  bowel,  but  it  does  not  appear  that  they  individually  form 
perfect  rings. 

This  muscular  tunic  becomes  gradually  thinner  towards  the  lower 
part  of  the  small  intestine.  It  is  pale  in  colour,  and  is  composed  of 
plain  muscular  fibres.  The  progressive  contraction  of  these  fibres, 
commencing  in  an}^  part  of  the  intestine,  and  advancing  in  a down- 
ward direction,  produces  the  peculiar  vermicular,  or  'peristaltic  move- 
ment, by  which  the  digestive  mass  is  forced  onwards  through  the 
canal.  In  this  movement  the  circular  fibres  are  mainly  concerned ; 
but  the  longitudinal  fibres  also  aid  in  it;  and  those  found  along  the 
free  border  of  the  intestine  will  evidently  straighten  or  unfold,  as  it 
were,  its  successive  convolutions. 

The  cellular  coai  of  the  small  intestine  is  a tolerably  distinct  and 
whitish  layer,  of  a loose  texture,  which  is  connected  more  firmly  with 
the  mucous  than  with  the  muscular  coat,  between  which  two  it  is 
placed.  By  turning  a portion  of  the  intestine  inside  out,  and  then 
blowing  forcibly  into  the  cavity,  the  cellular  tunic  may  be  infiated,  the 
air  being  driven  into  its  areolar  tissue,  through  the  part  at  which  the 
peritoneal  investment  is  wanting.  This  cellular,  or,  as  it  is  by  some 
named,  submucous  coat,  supports  the  mucous  membrane,  and  forms  a 
sort  of  layer  in  which  the  vessels  divide  and  subdivide  into  smaller 
branches  preparatory  to  entering  the  mucous  tissue.  It  consists  of 
filamentous  cellular  tissue,  mixed  with  fine  elastic  fibres. 

The  internal  or  mucous  coat  is  characterized  by  presenting  all  over 
its  inner  surface  a fine  fiocculent,  or  shaggy  appearance,  like  the  pile 
upon  velvet,  owing  to  its  being  covered  with  multitudes  of  minute 
processes,  named  villi;  hence  it  is  also  named  the  villous  coat.  It  is 


INTESTINAL  VILLI. 


455 


one  of  the  most  vascular  membranes  in  the  whole  body,  and  it  is 
naturally  of  a reddish  colour  in  the  upper  part  of  the  small  intestine, 
but  becomes  paler,  and  at  the  same  time  thinner  towards  the  lower 
end.  It  presents  for  further  consideration,  1.  the  epithelium;  2.  the 
\arge  folds  called  valvules  conniventes;  3,  the  villi;  4.  the  glands;  and 
5.  the  vessels. 

1.  Epithelium. — Every  part  of  the  surface  is  covered  by  a thin, 
transparent  epithelium,  of  the  columnar  or  cylindrical  kind.  The 
prismatic  particles  of  this  covering  are  represented  in  fig.  454, 

2.  Valvules  Conniventes. — The  folds  and  wrinkles  found  upon  the 
inner  surface  of  the  oesophagus  and  stomach  may  be  completely  obli- 
terated by  full  distension  of  those  parts  of  the  alimentary  canal.  In 
the  lining  membrane  of  the  small  intestine,  hov^ever,  there  exist, 
beside  such  effaceable  folds,  other  permanent  ones,  which  cannot  be 
obliterated,  even  when  the  tube  is  forcibly  distended.  These  perma- 
nent folds  are  the  valvules  conniventes,  or  valves  of  Kerkring.  They 
are  crescentic  projections  of  the  mucous  membrane,  placed  trans- 
versely to  the  course  of  the  bowel,  each  of  them  reaching  only  about 
one-half  or  two-thirds  of  the  distance  around  the  interior  of  the  tube, 
and  following  closely  upon  one  another  along  the  intestine. 

The  largest  of  these  valves  are  about  two  inches  long  and  one-third 
of  an  inch  w’ide  at  the  middle  or  broadest  part;  but  the  greater  num- 
ber are  under  these  dimensions.  Large  and  small  valves  are  often 
found  to  alternate  with  each  other.  Some  of  them  are  bifurcated  at 
one  end,  and  others  terminate  abruptly,  appearing  as  if  suddenly  cut 
otf.  Each  valve  consists  of  a fold  of  the  mucous  membrane,  that  is, 
of  two  layers  placed  back  to  back,  united  together  by  cellular  tissue. 
They  contain  no  muscular  fibres,  and  are  therefore  not4jontractile. 
Being  extensions  of  the  mucous  membrane,  they  serve  to  increase  the 
absorbent  surface  to  which  the  food  is  exposed,  and  at  the  same  time 
they  contribute  to  delay  its  passage  along  the  intestine. 

There  are  no  valvulae  conniventes  quite  at  the  commencement  of 
the  duodenum;  about  an  inch  or  somewhat  more  below  the  pylorus 
they  begin  to  appear ; beyond  the  point  at  which  the  bile  and  pancre- 
atic juice  are  poured  into  the  duodenum  they  are  very  large,  regu- 
larly crescentic  in  form,  and  placed  near  to  each  other;  they  conti- 
nue thus  through  the  rest  of  the  duodenum  and  along  the  upper  half  of 
the  jejunum;  below  that  point  they  begin  to  get  smaller  and  further 
apart ; and  finally,  towards  the  middle  of  the  ileum,  having  gradually 
become  more  and  more  irregular  and  indistinct,  sometimes  even  ac- 
quiring a longitudinal  direction,  they  altogether  disappear, 

3.  Villi. — The  villi,  peculiar  to  the  small  intestine,  which  give  to  its 
internal  surface  the  velvety  or  villous  appearance  already  spoken  of, 
are  small,  elongated,  and  highly  vascular  processes,  which  are  found 
situated  closely  together  over  every  part  of  the  mucous  membrane, 
upon  the  valvulae  conniventes,  as  well  as  between  them.  (See  fig.  455.) 
They  are  best  displayed  by  putting  a piece  of  intestine,  well  cleansed 
from  its  mucus,  under  water,  and  examining  it  with  a simple  lens. 
The  prevalent  form  of  the  villi  is  that  of  minute,  flattened,  triangular 
processes;  others  are  conical  or  cylindrical,  or  even  clubbed  at  the 


456 


INTESTINAL  VILLI. 


free  extremity.  Two  or  even  three  villi  are  occasionally  seen  con- 
nected together  at  their  base. 

Their  length  varies  from  ^th  to  of  a line,  or  even  more ; and  the 
broad  flattened  kinds  are  about  gth  or  ^th  of  a line  wide,  and  ^'^th  or 
a^th  of  a line  thick.  They  are  largest  and  most  numerous  in  the  duo- 
denum and  jejunum,  and  become  gradually  shorter,  smaller,  and  fewer 
in  number  in  the  ileum.  In  the  upper  part  of  the  small  intestine 
K rause  has  estimated  their  number  at  fron)  50  to  !)0  in  the  square  line; 
and  in  the  lower  part  at  from  40  to  70  in  the  same  space : he  calcu- 
lates their  total  number  to  be  at  least  four  millions. 

The  structure  of  these  villi  is  complicated  : each  consists  of  a pro- 
longation of  the  simple  membrane,  which  forms  the  surface  of  the 
proper  mucous  layer,  covered  by  epithelium  and  inclosing  blood-ves- 
sels and  lacteal  vessels,  with  a greater  or  less  number  of  small  granu- 
lar  corpuscles  and  fat  globules,  of  various  sizes : nerves  have  not  yet 


Fig-.  453. 


Magnified  view  of  the  blood  vessels  of  the  intestinal  villi,  showing  an  artery  and  vein,  and  a 
superficial  capillary  network.  After  a preparation  injected  by  Lieberkuehn. 

been  demonstrated  in  the  villi,  though  they  probably  are  not  wanting. 
Each  villus  receives  one  or  more  small  arterial  twigs,  which  divide, 
and  form  upon  its  surface,  beneath  the  epithelium  and  limiting  mem- 
brane, a fine  capillary  network,  from  which  the  blood  is  relumed  for 
the  most  part  by  a single  vein.  The  villi  also  contain  absorbent  ves- 
sels, which  at  the  base  of  each  villus  pass  into  the  general  network  of 
the  lacteals  of  the  mucous  membrane.  Their  mode  of  origin  within 
the  villi  is  not  yet  determined  with  certainty.  By  most  old  observers, 
as  Lieberkuehn,  Hunter,  Cruikshank,  and  Hewson,  the  lacteals  were 
supposed  to  commence  at  the  free  surface  of  the  villi  by  one- or  more 
open  mouths  ; but  all  the  modifications  of  this  opinion  are  now  given 
up,  and  the  best,  authorities  agree  in  believing  that  they  form  a closed 
system  of  vessels.  This  view,  indeed,  has  been  advocated  by  Mas- 
cagni, Albert  Meckel,  and  Rudolphi,  who  considered  that  they  com- 
menced by  a network.  Henle  states  that  he  has  found  only  a single 
lacteal  vessel,  with  a free,  distended,  but  closed  extremity  in  each 
cylindrical  villus,  and  two  such  vessels  not  anastomosing  together  in 
the  broader  villi.  Krause  has  figured  the  main  lacteal  of  a villus  as  | 
beginning  by  several  branches,  some  having  free  and  closed  extremities,  | 
and  others  joining  in  a network  ; but  it  is  questionable  whether  this 


PEYER’S  GLANDS. 


457 


appearance  may  not  be  owing  to  reticular  vessels  imperfectly  filled. 
The  epithelium  (fig.  454)  forms  a thin,  transparent,  but  very  distinct 


Fig.  454. 


Epithelium  of  small  intestine,  magnified.  (Henle.) — a.  Ideal  representation  of  the  surface  of  a 
villus,  showing  the  ends  of  the  epithelium  particles,  a,  b.  Columns  of  epithelium  from  the  in- 
testine, magnified,  c.  Viewed  by  their  broad  free  extremity.  D.  Seen  in  a transverse  section 
of  an  intestinal  villus.  (From  Henle.) 


layer  upon  the  surface  of  the  villi,  (a.)  It  resembles  the  epithelial 
covering  of  the  rest  of  the  mucous  membpane,  and  consists  of  elon- 
gated, prismatic,  columnar  particles  (a  b c),  arranged  compactly  to- 
gether, and  perpendicularly  to  the  surface  (d). 

4.  Glands. — The  glandular  structures  found  in  the  mucous  coat  of 
the  small  intestine  are  the  crypts  or  follicles  of  Lieberkuehn,  the  soli- 
tary glands,  the  patches  of  Peyer’s  glands,  and  Brunner’s  glands,  the 
last  being  peculiar  to  the  duodenum. 

The  crypts  of  Lieberkuehn,  the  smallest  of  these  glandular  structures, 
are  found  in  every  part  of  the  small  intestine,  between  the  villi  and 
surrounding  the  larger  glands.  They  consist  of  minute  tubes,  closed 
at  their  attached  extremity,  and  placed  more  or  less  perpendicularly  to 
the  surface,  upon  which  they  open  by  little  orifices.  (See  figs.  455, 
456.)  They  appear  to  be  analogous  to  the  tubuli  of  the  stomach,  but 
they  are  invariably  simple  in  form,  and  are  placed  further  apart  from 
each  other.  Similar  tubules  are  found  in  the  large  intestine  also. 
The  crypts  of  Lieberkuehn  vary  in  length  from  the  J^th  to  the  j'^th  of 
a line,  and  their  diameter  is  about  of  a line.  The  walls  of  the 
tubes  are  thin,  and  lined  with  a columnar  epithelium  : their  contents 
are  fluid  and  transparent,  with  granules  interspersed.  These  crypts 
are  sometimes  filled  with  a whitish  substance,  which  most  probably 
consists  chiefly  of  desquamated  epithelium  and  mucus. 

The  agminated  glands,  or  glands  of  Peyer,  (who  discovered  and 
described  them  in  1677,)  are  found  in  groups  or  patches,  having  an 
oblong  figure,  and  varying  from  half  an  inch  to  two  or  even  four 
inches  in  length,  and  being  about  half  an  inch  or  rather  more  wide. 
These  patches  are  placed  lengthways  in  the  intestine  at  that  part  of 
the  tube  most  distant  from  the  mesentery ; and  hence,  to  obtain  a view 
of  them,  the  bowel  should  be  opened  along  its  attached  border. 

The  patches  of  Peyer’s  glands  (see  fig.  455  and  its  description)  con- 
sist of  groups  of  small,  round,  flattened  vesicles  or  capsules,  usually 
filled  with  a whitish  semi-fluid  matter,  and  situated  beneath  the  mucous 
membrane,  the  surface  of  which  is  depressed  into  little  shallow  pits, 

VOL.  II.  39 


458 


SOLITARY  GLANDS. 


at  or  rather  under  the  bottom  of  which  the  capsules  are  placed.  The 
intermediate  surface  of  the  membrane  is  beset  with  villi  and  Lieber- 


Fig.  455.  Fig.  456. 


Fig.  455.  Enlarged  view  of  a part  of  a patch  of  Peyer’s  glands.  (Boehm.)  It  shows  the  diffe- 
rent forms  of  the  individiiat  vesicles,  the  zone  of  foramina  belonging  to  Lieberkuehn's  follicles 
around  each,  the  mouths  of  other  of  those  follicles  and  numerous  villi  situated  between  the  vesi- 
cles, not  upon  them,  and,  lastly,  the  surrounding  darker  part  of  the  mucous  membrane  beset 
merely  with  villi  and  follicles. 

Fig.  456.  Solitary  gland  of  the  small  intestine,  magnified.  (Boehm.)  The  surface  is  beset 
with  villi : the  mouths  of  numerous  crypts  of  Lieberkuehn  are  also  seen. 

kuehn’s  crypts:  the  villi  are  also  sometimes  found  even  over  the  cap- 
sules, and  the  crypts  are  collected  in  circles  around  the  capsules,  but 
do  not  communicate  with  them.  In  some  subjects  these  small  capsules 
are  found  almost  empty,  and  then  they  are  difficult  of  detection.  They 
are  usually  entirely  closed ; but  it  has  been  supposed  that  they  open 
from  time  to  time  to  discharge  their  contents  into  the  intestine,  for 
Krause  has  observed  that  in  the  pig  they  are  occasionally  open,  and  a 
similar  observation  has  since  been  made  by  Dr.  Allen  Thomson,  not 
only  in  the  pig,  but  in  the  human  intestine  also. 

Opposite  to  the  patches  of  Peyer’s  glands,  the  mucous  and  cellular 
coats  of  the  intestine  adhere  more  closely  together  than  elsewhere,  so 
that  in  those  situations  it  is  impossible  to  inflate  the  cellular  coat.  The 
corresponding  parts  of  the  intestine  are  also  exceedingly  vascular;  a.id 
the  lymphatic  vessels  form  plexuses,  which  correspond  in  figure  with 
the  patches  and  may  be  very  readily  injected. 

In  all,  there  are  from  twenty  to  thirty  of  these  oblong  patches. 
They  are  larger  and  placed  at  shorter  distances  from  each  other,  in 
the  lower  part  of  the  ileum  ; but  in  the  upper  portion  of  that  intestine 
and  in  the  lower  end  of  the  jejunum,  the  patches  occur  less  and  less 
frequenily,  become  smaller,  and  are  of  a nearly  circular  form. 

Still  smaller  irregularly  shaped  clusters  of  these  capsules  are  found 
scattered  throughout  the  intestine,  and  may  be  regarded  as  transitions 
to  the  next  form  of  glands,  named  solitary,  which  differ  from  the  ag- 
minated  glands  only  in  the  circumstance  of  being  separate. 

The  solitary  glands  (glandulse  solitarise)  are  soft,  white,  rounded, 
and  slightly  prominent  bodies,  about  the  size  of  a millet  seed,  which 
are  found  scattered  over  the  mucous  membrane  in  every  part  of  the 


DUODENUM. 


459 


small  intestine.  They  are  found  on  the  mesenteric  as  well  as  on  the 
free  border,  between  and  upon  the  valvuloe  conniventes,  and  are  rather 
more  numerous  in  the  lower  portion  of  the  bowel.  These  small  glands 
have  no  orifice,  but  consist  of  closed  vesicles  or  capsules  (fig.  456), 
exactly  resembling  those  forming  the  clusters  of  Peyer’s  glands,  having 
rather  thick  but  easily  destructible  walls,  and  usually  containing  in 
their  interior  an  opaque,  whitish  fluid,  which  abounds  in  fine  granules. 
The  free  surface  of  the  capsules,  which  is  slightly  elevated  when  they 
are  full,  is  beset  with  the  intestinal  villi;  and,  placed  around  them 
very  irregularly,  are  seen  the  open  mouths  of  the  crypts  of  Lieber- 
kuehn. 

The  nature  of  the  solitary  and  agminated  glands  is,  after  all,  very 
obscure,  and  their  use  not  understood.  From  the  observations  of 
Krause  and  Thomson,  it  is  to  be  presumed  that  their  thick  and  granu- 
lar contents  are  poured  from  time  to  time  into  the  intestinal  canal. 

Brunner's  glands  are  small  rounded  compound  glands,  first  pointed 
out  by  Brunner,  which  exist  in  the  duodenum,  where  they  are  most 
numerous  at  the  upper  end  ; according  to  BLuschke,  they  are  also  found 
quite  at  the  commencement  of  the  jejunum.  They  are  imbedded  in 
the  cellular  tunic,  and  may  be  exposed  by  dissecting  off  the  muscular 
coat  from  the  outside  of  the  intestine.  They  are  true  compound 
glands,  consisting  of  minute  lobules,  and  containing  branched  ducts, 
which  open  upon  the  inner  surface  of  the  intestine.  Their  secretion 
has  not  been  examined,  but  it  is  probably  of  importance  in  the  diges- 
tive process. 

5.  Blood-vessels  and  absorbents. — The  branches  of  the  mesenteric 
artery,  having  reached  the  attached  border  of  the  intestine,  pass  round 
its  sides,  dividing  into  numerous  ramifications  and  frequently  anasto- 
mosing at  its  free  border.  Most  of  the  larger  branches  run  imme- 
diately beneath  the  serous  tunic  : many  pierce  the  muscular  coat,  sup- 
plying it  with  vessels  as  they  pass,  and  having  entered  the  submucous 
cellular  layer,  ramify  in  it,  so  as  to  form  a close  network,  from  which 
still  smaller  vessels  pass  on  into  the  mucous  coat,  and  terminate  in 
the  capillary  network  of  the  folds,  villi,  and  glands  of  that  membrane, 
which  is  the  most  vascular  of  all  the  intestinal  tissues.  The  fine  ca- 
pillaries of  the  muscular  coat  are  arranged  in  two  layers  of  oblong 
meshes,  which  accompany  and  correspond  in  direction  with  the  lon- 
gitudinal and  circular  muscular  fibres.  The  veins  accompany  the 
arteries. 

The  absorbents  are  also  very  numerous,  and  consist  of  a superficial 
and  a deep  set,  which  commence  by  a network  on  the  mucous  and 
serous  surfaces  of  the  bowel.  The  superficial  network  forms  longitu- 
dinal meshes  arranged  like  the  fibres  of  the  external  muscular  layer; 
while  the  deep  set,  in  which  the  lacteals  of  the  villi  terminate,  form  a 
netw'ork  with  meshes  arranged  transversely  like  the  circular  muscular 
fibres.  The  two  sets  unite  freely  together,  and  at  the  attached  border 
of  the  intestine  end  in  numerous  large  vessels,  w'hich  pass  off  between 
the  layers  of  the  mesentery,  and  enter  the  mesenteric  glands. 

, THE  DUODENUM. 

The  duodenum  (fig.  473,  d)  extends  from  the  pylorus  {p)  to  the 


460 


DUODENUM. 


place  -where  the  superior  mesenteric  vessels  (the  artery  is  marked  n), 
coming  forwards  beneath  the  lower  border  of  the  pancreas,  cross  ver- 
tically over  the  intestinal  tube  to  reach  the  root  of  the  mesentery. 

This  is  the  shortest  and  widest  part  of  the  small  intestine.  It  mea- 
sures only  8 or  10  inches,  or  nearly  about  the  breadth  of  twelve  fingers ; 
hence  its  name. 

Its  diameter  varies  between  an  inch  and  a half,  and  an  inch  and 
three  quarters.*  The  course  of  the  duodenum  is  also  peculiar,  for  it 
describes  a single  large  curve  somewhat  resembling  a horseshoe,  the 
convexity  of  which  is  turned  towards  the  right,  whilst  the  concavity 
is  in  the  opposite  direction,  and  embraces  the  head  of  the  pancreas. 

It  is  also  placed  more  deeply,  and  held  more  fixedly  in  its  position 
than  the  rest  of  the  small  intestine.  It  has  no  mesentery,  and  is 
covered  only  partially  by  the  peritoneum.  Its  muscular  coat  is 
thicker;  and  its  mucous  membrane  the  seat  of  the  compound  glands 
of  Brunner.  Lastly,  the  common  bile-duct  and  the  pancreatic  duct 
open  into  this  part  of  the  intestinal  canal. 

Three  portions  of  the  duodenum,  differing  from  each  other  in  their 
course  and  connexions,  are  separately  described  by  anatomists;  viz., 
the  ascending,  descending,  and  transverse  portions. 

The  first,  or  ascending  portion,  which  is  about  two  inches  long, 
commences  at  the  pylorus,  and  passing  upwards,  backwards,  and  to 
the  right  side,  reaches  as  far  as  beneath  the  neck  of  the  gall-bladder, 
where  the  intestine  bends  suddenly  downwards.  This  first  portion  of 
the  duodenum  is  for  the  most  part  free,  and  entirely  surrounded  by  the 
peritoneum.  Above,  and  in  front  of  it,  are  the  liver  and  gall-bladder, 
and  it  is  commonly  found  stained  by  the  exudation  of  bile  from  the 
latter  a few  hours  after  death.  Behind  it,  is  the  hepatic  duct,  with 
the  blood-vessels  passing  up  to  the  liver. 

The  second,  or  descending  portion,  commencing  at  the  bend  below 
the  neck  of  the  gall-bladder,  passes  vertically  downwards  in  front  of 
the  right  kidney  as  low  as  the  second  or  third  lumbar  vertebra,  where 
the  bowel  turns  across  to  the  left  to  form  the  transverse  portion.  This 
part  of  the  duodenum  is  the  least  perfectly  invested  by  the  peritoneum, 
which  covers  only  its  anterior  surface, — the  posterior  surface  being 
connected  to  the  right  kidney  and  the  vertebral  column,  by  cellular.  ^ 
tissue.  In  front  is  the  transverse  colon  and  meso-colon,  the  upper  layer  i 
of  which  is  continuous  with  the  peritoneal  covering  of  the  duodenum,  f 
To  the  left  is  the  head  of  the  pancreas,  which  adapts  itself  to  the  shape 
of  the  intestine  on  that  side.  The  common  bile-duct  descends  behind  ^ 
the  left  border  of  this  part  of  the  duodenum,  and  together  with  the  pan-  g 
creatic  duct,  which  accompanies  it  for  a short  distance,  perforates  the 
coats  of  the  intestine  obliquely  at  the  lower  part  of  its  left  or  concave 
border.  In  the  interior  of  this  part  of  the  intestine,  the  valvulae  conni- 
ventes  begin  to  appear  ; and  an  eminence  or  papilla  found  about  ffur 
inches  below  the  pylorus,  on  the  inner  and  back  part  of  the  intestine, 
marks  the  situation  of  the  common  orifice  of  the  biliary  and  pancre- 
atic ducts. 

* These  and  other  measurements  relating  to  the  intestinal  canal  are  given  on  the  au-  1 
thority  of  Huschke. 


JEJUNUM— ILEUM. 


461 


The  third,  or  transverse  portion,  somewhat  the  longest  and  narrow- 
est, crosses  obliquely  from  right  to  left,  in  front  of  the  second  lumbar 
vertebra,  ascending  a little  so  as  to  end  in  the  jejunum  at  the  left  side 
of  that  bone.  It  is  placed  immediately  behind  the  root  of  the  trans- 
verse meso-colon,  the  two  layers  of  which  passing,  the  one  upwards, 
and  the  other  down,  afford  it  a covering  in  front.  Behind,  it  is  at- 
tached by  cellular  tissue  to  the  vertebral  column,  the  pillars  of  the 
diaphragm,  the  vena  cava,  and  the  aorta.  Along  its  upper  border  it 
is  connected  by  vessels  and  cellular  tissue  with  the  pancreas.  The 
superior  mesenteric  vessels  pass  from  beneath  the  pancreas  over  the 
intestine  at  the  point  where  it  terminates  in  the  jejunum. 

Vessels  and  nerves, — The  vessels  which  supply  the  duodenum  are 
derived  from  the  superior  pancreatico-duodenal  and  pyloric  branches 
of  the  hepatic  artery,  and  from  the  inferior  pancreatico-duodenal 
branch  of  the  superior  mesenteric  artery.  Its  veins  open  into  the 
gastro-duodenal  and  superior  mesenteric  vein.  Offsets  from  the  solar 
plexus,  directed  along  the  arteries,  supply  it  with  nerves. 

THE  JEJUNUM  AND  ILEUM. 

jejunum,  so  called  from  its  being  generally  found  empty  after 
death,  follows  the  duodenum,,  and  includes  the  upper  two-fifths  of  the 
remainder  of  the  small  intestine ; while  the  succeeding  three-fifths 
constitute  the  ileum,  so  named  from  its  numerous  coils  or  convolutions. 
Both  the  jejunum  and  the  ileum  are  attached  and  supported  by  the 
mesentery.  The  convolutions  of  the  jejunum  are  situated  in  part  of 
the  umbilical  and  left  iliac  regions  of  the  abdomen  ; while  the  ileum 
occupies  part  of  the  umbilical  and  right  iliac  regions,  together  with 
the  hypogastric,  and  even  descends  into  the  pelvis,  from  which  its 
lower  end,  supported  by  the  mesentery,  which  is  here  very  short, 
ascends  obliquely  to  the  right  and  somewhat  backwards,  over  the 
corresponding  psoas  muscle,  and  ends  in  the  right  iliac  fossa,  by 
opening  into  the  inner  side  of  the  commencement  of  the  large  intestine. 
There  is  no  defined  limit  between  the  jejunum  and  the  ileum,  but  the 
character  of  the  intestine  gradually  changes  from  its  upper  to  its  lower 
end,  so  that  a comparison  of  portions  of  the  two  intestines,  remote 
from  each  other,  presents  certain  well-marked  differences.  Thus,  the 
jejunum  is  wider,  and  its  coats  are  thicker ; it  is  more  vascular,  and 
therefore  it  has  a deeper  colour ; its  valvulae  connivenles  are  long, 
wide,  and  numerous  ; and  the  patches  of  Peyer’s  glands  are  smaller, 
less  frequent,  and  mostly  confined  to  its  lower  part.  The  ileum,  on 
the  other  hand,  is  narrower;  its  coats  are  thinner  and  paler;  the  val- 
vulag  conniventes  are  small,  and  gradually  cease  towards  its  lower 
end;  lastly,  the  groups  of  Peyer’s  glands  are  larger  and  more  nume- 
rous. The  diameter  of  the  jejunum  varies  from  one  inch  and  a half 
to  one  inch  ; that  of  the  ileum  from  one  inch  and  a quarter  to  less 
than  an  inch.  A given  length  of  the  jejunum  accordingly  weighs 
more  than  the  same  of  the  ileum. 

Vessels  and  nerves. — The  jejunum  and  ileum  receive  their  numerous 
vessels  from  the  superior  mesenteric  artery  and  vein.  Their  nerves 
descend  along  the  arterial  branches  from  the  solar  plexus. 

39* 


462 


LARGE  IlSTESTINE. 


THE  LARGE  INTESTINE. 

The  large  intestine  (intestinum  crassum:  fig.  448,®*"  which  ex- 
tends from  the  termination  of  the  ileum  to  the  anus,  is  distinguished 
from  the  small  intestine  by  its  direction,  its  size,  and  its  sacculated 
form.  It  differs  also  in  the  thickness  and  structure  of  its  muscular 
and  mucous  coats. 

It  commences  in  the  right  iliac  fossa,  and  ascends  through  the 
lumbar  region  into  the  right  hypochondrium  ; then,  turning  suddenly 
to  the  left,  it  passes  across  the  front  of  the  abdomen,  opposite  to  the 
confines  of  the  epigastric  and  umbilical  regions,  into  the  left  hypo- 
chondrium ; again  altering  its  direction,  it  bends  downwards  and 
descends  through  the  left  lumbar  to  the  left  iliac  region,  where  it 
makes  a double  turn  upon  itself;  finally,  it  dips  into  the  pelvis,  and 
following  the  front  of  the  sacrum  and  coccyx,  terminates  at  the  anus. 
In  this  course,  the  large  intestine  describes  the  greater  part  of  a circle, 
which  occupies  the  several  regions  already  mentioned,  reaches  as  hic;h 
as  the  liver  and  stomach,  and  surrounds  the  convolutions  of  the  small 
intestine. 

The  large  intestine  is  divided  by  anatomists  into  the  caecum  (inclu- 
ding the  vermiform  appendix),  the  colon,  and  the  rectum  ; and  the 
colon  is  again  subdivided,  according  to  its  direction,  into  four  parts, 
called  the  ascending,  transverse,  and  descending  colon,  and  the  sig- 
moid flexure. 

The  large  intestine  is  held  in  its  position,  in  some  places  by  perito- 
neal folds  resembling  the  mesentery  ; and,  in  others,  by  a partial 
covering  of  peritoneum,  and  where  this  is  deficient,  by  cellular  tissue, 
which  connects  it  to  the  back  of  the  abdominal  and  pelvic  caviiies. 
On  the  whole  it  is  more  fixed,  and  therefore  less  liable  to  displacement, 
than  the  small  intestine. 

The  length  of  the  large  intestine  is  usually  about  five  or  six  feet; 
being  about  one-fifth  of  the  whole  length  of  the  intestinal  canal.  Its 
diameter,  which  greatly  exceeds  that  of  the  small  intestine,  varies  at 
different  points  from  two  inches  and  a half  to  about  one  inch  and  a 
half.  It  diminishes  gradually  from  its  commencement  at  the  csecum, 
to  its  termination  at  the  anus  ; excepting  that  there  is  a well-marked 
dilatation  of  the  rectum  just  above  its  lower  end.  i 

In  outward  form,  the  greater  part  of  the  large  intestine  differs  re-  I 
markably  from  the  small  intestine;  for,  instead  of  representing  an  even  i 
cylindrical  tube,  its  surface  is  thrown  into  numerous  sacculi,  marked  J 
off  from  each  other  by  intervening  constrictions,  and  arranged  in  tlireekif 
longitudinal  rows,  separated  by  three  flat  bands  of  longitudinal  mus- 
cular  fibres.  This  sacculated  structure  is  not  found  in  the  rectum. 

Structure. — The  walls  of  the  large  intestine  consist  of  four  coats, 
resembling  those  of  the  small  intestine,  namely,  the  serous,  muscular, 
cellular,  and  mucous. 

The  external  or  serous  coat,  derived  from  the  peritoneum,  forms  a 
complete  investment  only  to  certain  portions  of  the  intestine;  in  other 
parts  the  serous  covering  is  incomplete;  and  at  the  lower  end  of  die 
tube  it  is  entirely  wanting.  Along  the  colon,  and  upper  part  of  the 


STRUCTURE  OF  LARGE  UVTESTINE. 


463 


rectum,  the  peritoneal  coat  is  developed  into  numerous  little  pouches, 
filled  with  adipose  tissue.  These  fatty  processes  are  named  appendices 
epiploicce. 

The  muscular  coat,  like  that  of  every  part  of  the  intestinal  canal, 
consists  of  external  longitudinal  and  internal  circular  fibres.  The 
longitudinal  fibres,  though  found  in  a certain  amount  all  around 
the  intestine,  are,  in  the  caecum  and  colon,  principally  collected  into 
three  remarkable  flat  longitudinal  bands.  These  bands,  sometimes 
called  the  ligaments  of  the  colon,  are  about  half  an  inch  wide,  and 
half  a line  thick  ; they  commence  upon  the  bottom  of  the  caecum,  at 
the  attachment  of  the  vermiform  appendix,  and  may  be  traced  along 
the  whole  length  of  the  colon  as  far  as  the  commencement  of  the 
rectum,  where  they  spread  out,  so  as  to  surround  that  part  of  the  in- 
testinal tube  with  a continuous  layer  of  longitudinal  muscular  fibres. 
One  of  these  bands,  named  the  posterior,  is  placed  along  the  attached 
border  of  the  intestine  ; another  corresponds  with  its  anterior  border, 
and,  in  the  transverse  colon,  is  situated  at  the  attachment  of  the  great 
omentum ; whilst  the  third  band  {lateral)  is  found  along  the  free  side 
of  the  intestine,  that  is,  on  the  inner  border  of  the  ascending  and  de- 
scending colon,  and  on  the  under  border  of  the  transverse  colon.  It 
is  along  the  course  of  thi^  third  band  that  the  appendices  epiploicse  are 
most  of  them  attached.  Measured  from  end  to  end,  these  three  bands 
are  shorter  than  the  membranous  part  of  the  tube,  so  that  in  the 
intervals  between  the  bands  this  is  puckered  or  thrown  into  the  sacculi 
already  mentioned.  Accordingly,  if  the  longitudinal  bands  be  stripped 
off,  the  sacculi  are  obliterated,  and  the  intestine  is  lengthened.  The 
transverse  constrictions,  seen  outwardly  between  the  sacculi,  appear 
on  the  inside  of  the  intestine  as  sharp  ridges  separating  the  cells,  and 
are  composed  of  all  its  coats. 

The  circular  muscular  fibres  form  but  a thin  layer  over  the  general 
surface  of  the  cascum  and  colon,  but  are  accumulated  in  larger  num- 
bers between  the  sacculi.  In  the  rectum,  especially  towards  its  lower 
part,  the  circular  fibres  form  a very  thick  and  powerful  muscular 
layer. 

The  cellular  or  submucous  coat  requires  no  special  notice. 

The  mucous  membrane  is  on  the  whole  pale,  but  is  much  redder  and 
darker  in  the  rectum  than  elsewhere.  It  differs  from  the  lining  mem- 
brane of  the  small  intestine  in  having  no  folds,  like  the  valvulae  conni- 
ventes,  and  also  in  being  quite  smooth  and  destitute  of  villi.  Viewed 
with  a lens,  its  surface  is  seen  to  be  marked  all  over  by  the  orifices  of 
numerous  tubuli  (fig.  458,  c,  d),  resembling  those  of  the  stomach  and 
the  crypts  of  the  small  intestine.  These  follicles  are  arranged  per- 
pendicularly to  the  surface  of  the  membrane;  they  are  longer  and 
more  numerous,  and  are  placed  more  closely  together  and  at  more 
regular  intervals  than  those  of  the  small  intestine.  Their  orifices  are 
circular,  and  they  give  the  mucous  membrane  a cribriform  aspect. 

Besides  these,  there  are  scattered  over  the  surface  of  the  whole 
large  intestine  numerous  rounded,  whitish,  glandular  bodies,  about  ^ 
or  5 a line  in  diameter,  and  therefore  much  larger  than  the  tubuli. 
These  are  follicular  recesses  or  crypts  (fig.  457,  a,  b),  very  simple  in 


4G4 


C^CUM. 


Structure.  Their  orifice  is  narrowed,  but  it  leads  into  a dilated  cavity, 
having  thin  walls,  closely  surrounded  by  the  small  perpendicular 
tubuli.  They  are  most  abundant  in  the  cjBcum  and  in  its  vermiform 
appendix. 

Fig.  457.  Fig.  458. 


D 

1^ 


Fig.  4.57.  One  of  the  solitary  follicles  viewed  from  above  at  a,  and  seen  in  section  at  b; 
from  the  large  intestine.  (Boehm.) 

Fig.  458.  Tubnli  and  follicles  of  the  large  intestine,  magnified.  (Boehm  ) — c.  Tubnli,  of 
which  the  mucous  membrane  principally  consists.  D.  Matural  size  of  same  piece  of  roembmiie. 
1.  Their  orifices  seen  on  the  surface.  2.  Side  view  of  the  tubuli  themselves.  3.  Surface  of 
the  submucous  or  cellular  coat,  showing  small  pits  corresponding  with  the  closed  ends  of  the 
tubuli. 

The  epithelium,  which  covers  the  general  surface  of  the  mucous 
membrane,  and  lines  the  tubuli  and  follicles,  is  of  the  columnar  kind. 

THE  C iE  C TJM. 

The  ca3cum  (448,®)  is  that  part  of  the  large  intestine  which  is  situ- 
ated below  the  entrance  of  the  ileum  ; it  is  named  ccEcum,  or  the  blind 
gut  (caput  caecum  coli),  because  it  forms  a cul-de-sac,  or  short  rounded 
pouch  extending  downwards  from  the  commencement  of  the  colon, 
with  which  it  is  continuous  above,  without  any  line  of  demarcation. 
Its  length  is  about  inches,  and  its  diameter  nearly  the  same:  it  is 
the  widest  part  of  the  large  intestine. 

The  caecum  is  situated  in  the  right  iliac  fossa,  immediately  behind 
the  anterior  w'all  of  the  abdomen.  It  is  covered  by  the  peritoneum  in 
front,  below,  and  at  the  sides  ; but  behind  it  is  usually  destitute  of  peri- 
toneal covering,  and  is  attached  by  cellular  tissue  to  the  fascia  cover- 
ing the  right  iliacus  muscle.  In  this  case  the  caecum  is  comparatively 
fixed  ; but  in  other  cases  the  peritoneum  surrounds  it  almost  entirely, 
and  forms  a duplicature  behind  it,  called  the  meso-ccBcum. 

Proceeding  from  the  inner  and  back  part  of  the  caecum,  at  its  lower 
end,  is  a narrow,  round,  and  tapering  portion  of  the  intestine,  named 
the  appendix  ccsci,  or,  from  its  resemblance  to  a worm,  appendix  vcr- 
miformis  (*“).  This  process  (fig.  459,  p)  is  usually  about  the  width  of 
a large  quill  or  rather  more,  and  varies  from  three  to  six  inches  in 
length,  differing  much  in  its  dimensions  in  different  cases.  Its  general 
direction  is  upwards  and  inwards  behind  the  crecum,  and  after  describ- 
ing a few  slight  turns,  it  ends  in  a blunt  point.  It  is  retained  in  its 
position  by  a small  fold  of  peritoneum,  which  forms  a mesentery  for 
it.  This  cmcal  appendix  is  hollow  down  to  its  extremity  ; and  its 
cavity  communicates  with  that  of  the  ca3cum  by  a small  orifice,  some- 
times guarded  by  a fold  of  mucous  membrane.  Its  coats  are  the  same 


ILEO-CiECAL  VALVE. 


465 


as  those  of  the  ctecum,  and  quite  as  thick.  The  longitudinal  muscular 
fibres,  which  are  continuous  with  those  of  the  three  bands  described 
upon  the  csecum  and  colon,  form  a uniform  layer  around  the  appendix. 
Its  mucous  membrane  resembles  that  of  the  caecum,  but  it  is  abun- 
dantly provided  with  the  solitary  follicular  glands. 

In  the  early  embryo  there  is  at  first  no  caecum.  This  part  of  the 
bowel  gradually  grows  out  from  the  rest,  and  in  the  first  instance  forms 
a tube  of  uniform  calibre.  In  this  state  no  appendix  is  seen ; but  sub- 
sequently the  lower  part  of  the  tube,  relatively  speaking,  ceases  to 
grow,  and  becomes  the  vermiform  appendix,  whilst  the  upper  portion 
continues  to  be  developed  with  the  rest  of  the  intestine.  A distinct 
appendix  exists  in  the  ourang-outang  and  in  the  wombat,  but,  as  far 
as  is  known,  in  no  other  animal. 

Ileo-c(Ecal,  or  ileo-colic  valve. — The  lower  part  of  the  small  intestine 
(fig.  459,  i),  ascending  from  left  to  right,  and  from  before  backwards, 
enters  the  commencement  of  the  large  intestine,  with  a considerable 
degree  of  obliquity,  about  two  inches 
and  a half  from  the  bottom  of  the  459. 

caecum  (c),  and  opposite  the  junc- 
tion of  tbe  latter  with  the  colon  (o), 
above.  The  opening  leading  from 
the  ileum  into  the  large  intestine  is 
guarded  by  a valve,  composed  of 
two  segments,  or  folds  (e,  a).  This 
is  the  ileo-ccEcal,  or  ileo-colic  valve : 
it  is  also  called  the  valve  of  Bauhin 
and  the  valve  of  Tulpius,  though 
Fallopius  had  described  it  before 
either  of  those  anatomists. 

The  entrance  between  the  two 
segments  of  the  valve,  which  is  best 
displayed  by  laying  open  the  com- 
mencement of  the  large  intestine, 
along  the  right  side,  after  it  has  been 
distended  and  dried,  is  a narrow 
elongated  aperture,  of  a somewhat 

elliptical  form,  and  having  a nearly  intestines,  and,  the  CEecum  and  colon  being 

transverse  or  horizontal  direction.  displays  the  ileo-caecal  valve,  a. 

rni  . 1 r ! • ^ lower  segment,  e.  I he  upper  segment 

ine  anterior  end  ot  this  aperture,  of  the  valve,  c.  The  caecum,  o.  The  as- 
which  is  turned  slightly  to  the  lefi,  is  Cfndjng  colon.  %.  The  end  of  the  ileum,  p. 
rounded,  but  the  posterior  end  is  altered, 
narrow  and  pointed.  It  is  bounded 

above  and  below  by  two  prominent  semilunar  folds,  which  project  in- 
wards towards  the  caecum  and  colon.  The  lower  fold  {a)  is  the 
larger  of  the  two ; the  upper  (e)  is  placed  more  horizontally.  At  each 
end  of  the  aperture  these  folds  coalesce,  and  are  then  prolonged  as  a 
single  ridge  for  a short  distance  round  the  cavity  of  the  intestine, 
forming  the  frcena  or  retinacula  of  the  valve.  The  convex  attached 
border  of  the  upper  fold  corresponds  with  the  line  of  connexion  be- 
tween the  upper  surface  of  the  ileum  and  the  colon,  and  that  of  the 


Shows  the  junction  of  the  small  and  large 


466 


COLON. 


lower  fold  with  the  junction  of  the  under  surface  of  the  ileum  and  the 
cmcum.  Their  free  concave  margins  are  turned  towards  the  large 
intestine,  having  a slight  inclination  upwards,  and  are  brought  into 
apposition  when  the  cmcum  is  distended,  so  as  completely  to  close  the 
aperture  and  mechanically  prevent  any  influx  into  the  ileum. 

Each  segment  of  the  valve  consists  of  two  layers  of  mucous  mem- 
brane, continuous  with  each  other  along  the  free  margin,  and  includ- 
ing between  them,  besides  the  submucous  cellular  tissue,  a number 
of  muscular  fibres,  continued  from  the  circular  fibres  of  the  ileum  and 
from  those  of  the  large  intestine  also.  The  longitudinal  muscular 
fibres  and  the  peritoneal  coat  take  no  part  in  the  formation  of  the 
valve,  but  are  extended  ujninterruptedly  from 
other.  If,  indeed,  the  serous  tunic,  and  the  longij^pdinal  muscular 
fibres  be  divided,  the  ileum  may  be  drawn  out,  with  the  aid  of  a little 
cautious  dissection,  from  the 'side  of  the  large  intestine,  and  the  folds 
of  the  valve  will  be  completely  effaced, — the  small  intestine  seeming 
then  to  open  into  the  large,  by  a funnel-shaped  orifice  like  that  leading 
from  the  oesophagus  into  the  stomach. 

The  mucous  membrane  covering  the  surface  of  each  valvular  seg- 
ment which  is  turned  towards  the  ileum,  is  derived  from  the  lining 
membrane  of  that  intestine,  and  is  provided  with  its  characteristic 
villi;  while  the  other  surface,- turned  towards  the  large  intestine,  is 
smooth  and  destitute  of  villi,  and  is  more  regularly  marked  with  the 
orifices  of  the  small  tubuli.  These  differences  are  apparent  quite  up 
to  the  free  margin  of  the  valve,  where  the  two  kinds  of  mucous  meiii- 
brane  become  continuous. 

THE  COLON.  ^ 

The  right  or  ascending  colon  (fig.  448,“)  situated  in  the  right  lum- 
bar and  hypochondriac  regions,  commencing  at  the  caecum  opposite 
to  the  ileo-colic  valve,  ascends  vertically  to  the  under  surface  of  the 
liver,  near  the  gall-bladder,  where  it  advances  forwards  and  then 
turns  abruptly  to  the  left,  forming  what  is  named  the  hepatic  flexure 
of  the  colon.  The  ascending  colon  is  smaller  than  the  caecum,  but 
larger  than  the  transverse  colon.  It  is  overlaid  in  front  by  some  con- 
volutions of  the  ileum,  and  is  bound  down  firmly  by  the  peritoneum, 
which  passes  over  its  anterior  surface  and  its  sides,  and  generally 
leaves  its  posterior  surface  to  be  connected  by  cellular  tissue  with  the 
fascia  covering  the  quadratus  lumborum  muscle,  and  with  the  front  of 
the  right  kidney.  In  some  cases,  however,  the  peritoneum  passes 
nearly  round  it,  and  forms  a distinct  though  very  short  right  meso- 
colon. 

The  transverse  colon  passes  across  from  the  right  hypochon- 
drium,  through  the  upper  part  of  the  umbilical  region,  into  the  left 
hypochondrium.  Sometimes  it  is  found  as  low  as  the  umbilicus  or 
even  lower.  At  each  extremity  it  is  situated  deeply  towards  the  back 
part  of  the  abdominal  cavity,  but  in  the  middle  advances  forwards, 
and  lies  close  to  the  anterior  wall  of  the  abdomen.  Hence  it  describes 
an  arch,  the  concavity  of  which  is  turned  towards  the  vertebral  co- 
lumn ; and  it  has  accordingly  been  named  the  arch  of  the  colon. 


RECTUM. 


467 


Above,  the  transverse  colon  is  in  contact  with  the  under  surface  of 
the  liver,  the  gall-bladder,  the  great  curvature  of  the  stomach,  and  the 
lower  end  of  the  spleen.  Below  it,  are  the  convolutions  of  the  small 
intestine,  the  third  portion  of  the  duodenum  being  behind  it.  By  its 
posterior  border  it  is  attached  to  the  meso-colon,  a ver}’’  large  and 
wide  duplicature  of  the  peritoneum,  which  serves  to  connect  this  part 
of  the  large  intestine  to  the  back  of  the  abdominal  cavity,  at  the  same 
time  allowing  it  more  freedom  of  movement  than  the  other  parts.  The 
two  layers  of  the  meso-colon,  having  separated  to  enclose  the  trans- 
verse colon  and  form  its  peritoneal  coat,  meet  again  along  its  anterior 
border  and  become  continuous  w'ith  the  great  omentum,  which  there- 
fore lies  upon  the  intestine,  and  is  connected  wdlh  it.  The  lower  bor- 
der of  the  stomach  also  frequently  rests  upon  the  transverse  colon. 

The  left  or  descending  colon  is  continuous  with  the  left  extre- 
mity of  the  transverse  colon  by  a sudden  bend,  named  the  splenic  flex- 
ure. It  then  descends  almost  perpendicularly  through  the  left  hypo- 
chondriac and  lumbar  regions  to  the  left  iliac  fossa,  where  it  ends  in 
the  sigmoid  flexure.  The  peritoneum  affords  a covering  to  it  only  in 
front  and  at  the  sides,  whilst  behind  it  is  connected  by  cellular  tissue 
to  the  left  crus  of  the  diaphragm,  the  quadratus  lumborum  and  the  left 
kidney.  It  is  usually  concealed  behind  some  convolutions  of  the  je- 
junum. 

The  sigmoid  flexure  of  the  colon  (^*),  situated  in  the  left  iliac  fossa, 
consists  of  a double  bending  of  the  intestine  upon  itself  in  the  form  of 
the  letter  S,  immediately  before  it  becomes  continuous  with  the  rectum, 
at  the  margin  of  the  pelvis  opposite  to  the  left  sacro-iliac  symphysis. 
It  is  covered  all  round  by  the  peritoneum,  which,  however,  is  reflected 
from  it  behind  to  form  a distinct  meso-colon.  By  this  the  intestine  is 
attached  to  the  iliac  fossa,  but  it  is  very  movable.  It  is  placed  imme- 
diately behind  the  abdominal  parietes,  or  is  concealed  only  by  a few 
turns  of  the  small  intestine.  The  sigmoid  flexure  is  the  narrowest 
part  of  the  cojon. 

Vessels  and  Nerves. — The  caecum,  and  the  ascending  and  transverse 
colon,  receive  their  vessels  from  the  right  side  of  the  superior  mesen- 
teric artery;  and  the  descending  colon  and  sigmoid  flexure  from  the 
inferior  mesenteric.  The  veins  end  in  those  which  accompany  the 
arteries  just  named.  The  nerves  are  offsets  from  the  superior  and  in- 
ferior mesenteric  plexuses.  Lastly,  the  absorbents  enter  the  lymphatic 
glands  placed  along  the  blood-vessels. 

THE  RECTUM. 

The  lowest  portion  of  the  large  intestine,  named  the  rectum  (fig. 
448,“  and  fig.  478,  b b h),  extends  from  the  sigmoid  flexure  of  the  colon 
to  the  anus,  and  is  situated  entirely  within  the  true  pelvis,  at  its  back 
part. 

Commencing  opposite  to  the  left  sacro-iliac  junction  (fig.  478,  b), 
it  is  directed  at  first  obliquely  downwards,  and  from  left  to  right,  to 
gain  the  middle  line  of  the  sacrum.  It  then  changes  its  direction,  and 
curves  forward  in  front  of  the  lower  part  of  the  sacrum  and  the  coc- 
cyx, and  behind  the  bladder,  vesiculae  seminales,  and  prostate  in  the 


468 


STRUCTURE  OF  RECTUM. 


male  {h'),  and  at  the  back  of  the  cervix  uteri  and  vagina  in  the  female. 
Opposite  to  the  prostate  (p),  it  forms  another  turn,  and  inclines  down- 
wards and  backwards  (A)  to  reach  the  anus.  'The  intestinum  rectum, 
therefore,  is  not  actually  straight.  Seen  from  the  front,  the  upper  part 
of  the  rectum  presents  a lateral  inclination  from  the  left  to  the  median 
line  of  the  pelvis;  and  when  viewed  from  the  side  (as  in  fig.  476),  it 
offers  two  curves,  one  corresponding  with  the  hollow  front  of  the  sac- 
rum and  coccyx,  and  the  other  at  the  lower  end  of  the  bowel,  forming 
a shorter  turn  in  the  opposite  direction. 

Unlike  the  rest  of  the  large  intestine,  the  rectum  is  not  sacculated, 
but  is  smooth  and  cylindrical;  and  it  has  no  separate  longitudinal 
bands  upon  it.  It  is  about  six  or  eight  inches  in  length ; and  is  rather 
narrower  than  the  sigmoid  flexure  at  its  upper  end,  but  becomes  dilated 
into  a large  ampulla  or  reservoir,  immediately  above  the  anus. 

The  upper  part  of  the  rectum  is  in  contact  in  front  with  the  back  of 
the  bladder,  (or  uterus  in  the  female,)  unless  some  convolutions  of  the 
small  intestine  happen  to  descend  into  the  interval  between  them. 
This  part  is  surrounded  by  peritoneum  (r),  which  attaches  it  behind 
to  the  sacrum  by  a duplicature  named  the  meso-rectwn.  Lower  down, 
the  peritoneum  covers  the  intestine  in  front  and  at  the  sides,  and  then 
its  anterior  surface  only;  still  lower,  it  quits  the  intestine  altogether, 
and  is  reflected  forwards  to  ascend  upon  the  back  of  the  bladder  [a) 
in  the  male,  and  of  the  upper  part  of  the  vagina  and  the  uterus  in  the 
female.  In  passing  from  the  rectum  to  the  bladder,  the  peritoneum 
forms  a cul-de-sac  (r'),  which  extends  between  the  intestine  and  the 
bladder  to  within  a short  distance  of  the  prostate,  and  is  bounded  on 
the  sides  by  two  lunated  folds  of  the  serous  membrane. 

Below  the  point  where  the  peritoneum  ceases  to  cover  it,  the  rectum 
(at  b')  is  connected  to  surrounding  parts  by  cellular  tissue,  which  is 
mostly  loaded  with  fat.  In  this  way  it  is  attached  behind  to  the  fron‘ 
of  the  sacrum  and  the  coccyx,  and  at  the  sides  to  the  coccygei  and 
levatores  ani  muscles.  In  front,  it  is  in  immediate  connexion  with 
a triangular  portion  of  the  base  of  the  bladder;  on  each  side  of  this, 
with  the  vesiculm  seminales  (a) ; and  further  forwards,  with  the  under 
surface  of  the  prostate  (p).  Beyond  the  prostate,  where  the  rectum 
turns  downwards  to  reach  the  anus,  it  becomes  invested  by  the  fibres 
of  the  internal  sphincter,  and  embraced  by  the  levatores  ani  muscles, 
which  form  a support  for  it.  Lastly,  at  its  termination  it  is  surround- 
ed by  the  external  or  proper  sphincter  ani  muscles  (Ji).  In  the  female, 
this  lower  portion  of  the  rectum  is  firmly  connected  with  the  back  of 
the  vagina. 

Structure. — The  rectum  differs  in  some  respects  from  the  rest  of 
the  large  intestine,  viz.,  in  regard  to  its  muscular  and  mucous  coats. 

The  muscular  coat  is  much  thicker:  the  external  or  longitudinal 
fibres  form  a uniform  layer  around  it  and  cease  near  the  lower  end  of 
the  intestine ; the  internal  or  circular  fibres,  on  the  contrary,  become 
more  numerous  in  that  situation,  where  they  form  what  is  named  the 
internal  sphincter  muscle.*  The  longitudinal  fibres  are  paler  than  the 

* The  longitudinal  muscular  fibres  of  the  rectum,  after  reaching  the  lower  margin  of 
the  internal  sphincter,  turn  in  between  it  and  the  e-xternal  sphincter,  and  then  ascend  for 


MUSCLES  OF  ANUS. 


469 


circular  fibres,  but  both  layers  become  darker  and  redder  towards  the 
termination  of  the  bowel.  The  bands  composing  the  internal  sphincter 
muscle  are  found  to  contain  striped  muscular  fibres. 

The  mucous  membrane  of  the  rectum  is  thicker,  redder,  and  more 
vascular  than  that  of  the  colon;  and  it  moves  freely  upon  the  muscular 
coats — in  that  respect  resembling  the  lining  membrane  of  the  oesopha- 
gus. It  presents  numerous  folds  of  different  sizes,  and  running  in  va- 
rious directions,  nearly  all  of  which  are  effaced  by  the  distension  of 
the  bowel.  Near  the  anus  these  folds  are  principally  longitudinal,  and 
seem  to  depend  on  the  contraction  of  the  sphincter  muscles  outside 
the  loosely  connected  mucous  membrane.  The  larger  of  these  folds 
were  named  by  Morgagni  the  columns  of  the  rectum  {columncc  recti). 
Higher  up  in  the  intestine,  the  chief  folds  are  transverse  or  oblique. 
Three  prominent  folds,  larger  than  the  rest,  being  half  an  inch  or  more 
in  width,  and  having  an  oblique  direction  in  the  interior  of  the  rectum, 
have  been  pointed  out  specially  by  Mr.  Houston.*  One  of  these  pro- 
jects backwards  from  the  upper  and  fore  part  of  the  rectum,  opposite 
the  prostate  gland ; another  is  placed  higher  up,  at  the  side  of  the 
bowel;  and  the  third  still  higher.  From  the  position  and  projection 
of  these  folds,  they  may  more  or  less  impede  the  introduction  of  in- 
struments. 

Vessels  and  JVerves. — The  arteries  of  the  rectum  spring  from  three 
sources,  viz.,  the  superior  htemorrhoidal  branches  from  the  inferior 
mesenteric  ; the  middle  hasmorrhoidal  branches  from  the  internal  iliac 
directly  or  indirectly ; and,  lastly,  the  external  or  inferior  hmmorrhoi- 
dal  branch  from  the  pudic  arteiw.  The  veins  are  very  numerous,  and 
form  a complex  interlacement,  the  hsemorrhoidal  plexus,  around  the 
low’er  end  of  the  bowel  above  the  anus.  They  end  partly  in  the  in- 
ternal iliac  vein  by  branches  which  accompany  the  middle  hsemor- 
rhoidal  artery,  and  partly  in  the  inferior  mesenteric  vein.  Hence,  the 
blood  from  the  rectum  is  returned  in  part  into  the  vena  cava,  and  in 
part  into  the  portal  system.  The  lymphatics  enter  some  glands  placed 
in  the  hollow  of  the  sacrum,  or  those  of  the  lumbar  series.  The  nerves 
are  also  very  numerous,  and  are  derived  from  both  the  cerebro-spinal 
and  the  sympathetic  systems.  The  former  consist  of  branches  de- 
rived from  the  sacral  plexus;  and  the  latter,  of  offsets  from  the  infe- 
rior mesenteric  and  hypogastric  plexuses. 

THE  ANUS  AND  ITS  MUSCLES. 

The  anus,  or  lower  opening  of  the  alimentary  canal,  is  a dilatable 
orifice,  surrounded  internally  by  the  mucous  membrane,  and  externally 
by  the  skin,  w’hich  two  structures  here  become  continuous  w'ith  and 
pass  into  each  other.  The  skin  around  the  borders  of  the  anus,  which 
is  thrown  into  wrinkles  or  folds  during  the  closed  state  of  the  orifice, 
is  covered  w'ith  numerous  sensitive  papillee,  and  is  provided  with  hairs 
and  sebaceous  follicles. 

an  inch  or  two,  to  be  inserted  into  the  fibro-vascular  layer  of  the  mucous  membrane.  Many 
of  the  terminating  fibres  are  collected  into  fasciculi,  which  form  the  base  of  the  columns 
of  the  rectum.  Horner,  Spec.  Anat.  and  Hist.  vol.  ii.  p.  49,  Phil.  1846. — J.  L.] 

* Dublin  Hospital  Reports,  vol.  v. 

VOL.  II. 


40 


470 


SPHINCTER  ANI. 


Fig.  460. 


The  lower  end  of  the  rectum  and  the  margin  of  the  anus  are,  more- 
over, embraced  by  certain  muscles,  which  serve  to  support  the  bowel, 
and  to  close  its  anal  orifice.  These  muscles,  proceeding  from  within 
outwards,  are,  the  internal  sphincter,  the  levatores  ani  (with  which  we 
may  associate  the  coccygei),  and,  lastly  the  external  sphincter  ani. 

The  internal  sphincter  muscle  (sphincter  ani  internus)  is  a muscu- 
lar ring  or  rather  belt,  surrounding  the  lower  part  of  the  rectum,  an 
inch  above  the  anus,  and  extending  over  about  half  an  inch  of  the  in- 
testine. It  is  two  lines  thick,  and  is  paler  than  the  external  sphincter. 
Its  fibres  are  continuous  above  with  the  circular  muscular  fibres  of  the 
rectum,  and,  indeed,  it  consists  merely  of  those  fibres  more  numerously 
developed  than  elsewhere,  and  prolonged  down  further  than  the  exter- 
nal longitudinal  fibres.  Opposite  to  the  internal  sphincter,  the  mucous 
membrane  of  the  rectum  is  elevated  into  a ring. 

The  external  sphincter  (figs. 
460,  e,  478,  h;  sphincter  ani 
externus)  is  a flat  oval  muscle, 
placed  immediately  beneath  the 
skin  surrounding  the  margin  of 
the  anus.  It  is  elliptical  inform, 
being  about  an  inch  wide  oppo- 
site to  the  anus,  and  becoming 
narrow  at  its  posterior  and 
anterior  extremities,  which  are 
between  three  and  four  inches 
apart,  and  are  fixed,  one  to 
the  coccyx,  and  the  other  to 
the  middle  point  of  the  peri- 
naeum. 

Posteriorly,  it  is  attached  to 

Muscles  of  the  perin:E.il  region.  (Santorini.) — 1.  the  tip  and  back  of  the  COCCyX, 

3.  Ischial  spine  460,^)  by  means  of  a nar- 
n.  b,  b.  Bulbo-  X a ’ / J 

, c.  ischio-caver-  row  bundle  ot  tendinous  fibres: 
nosus.or  erector  penis.  c(,  rf.  Transversi  periniei.  -yvlfilst,  anteriorly,  in  front  of  the 
e.  bxiernal  sphincter  am.  f.  Coccygeus.  I,  1.  . ^ . 

Levatores  ani.  n.  Layer  of  fascia  covering  levator  clHUS,  clDOUt  midWSy  DCtWGOn 

ani.  .9.  Spongy  part  of  the  urethra.  The  probe  is  that  orifice  and  the  bulb  of  the 

urethra  (in  the  male),  it  becomes 
blended,  (near  the  probe  in  fig. 
460,)  through  the  medium  of  a common  fibrous  structure,  with  the 
transverse  muscles  of  the  perinseurn,  (d,)  and  with  the  muscles  em- 
bracing the  urethral  bulb,  {b,  b.)  In  the  female,  the  anterior  extre- 
mity of  the  external  sphincter  unites  with  the  constrictor  vulvae  and 
the  transversi  perinasi  muscles.  The  intermediate  and  wider  portion 
of  the  sphincter  is  disposed  like  other  orbicular  muscles,  and  is  com- 
posed of  fleshy  bundles,  which  embrace  the  intestine  and  intersect 
eabh  other,  or  unite  in  a commissure  before  and  behind  it. 

The  lower  or  external  surface  of  this  muscle  is  covered  only  by  the 
skin;  the  upper  or  internal  surface  is  in  contact  with  the  paler  fibres 
constituting  the  internal  sphincter,  and  also  with  some  cellular  tissue 


Ramus  of  ischium. — 2.  Coccyx, 
ami  tuberosity.  4.  Side  of  sacr 
cavernosus,  or  acceleraior  urinae. 


placed  beneath  the  central  fibrous  structure  of  the 
perineum. 


LEVATORES  ANI. 


471 


which  separates  it,  though  imperfectly,  from  the  lowest  fibres  of  the 
levatores  ani  muscles. 

The  action  of  the  external  and  internal  sphincters  is  sufficiently 
obvious. 

The  levatores  ani  muscles,  (fig.  460,  Z,  Z,)  one  right  and  the  other 
left,  are  two  broad  and  thin  muscular  layers,  which  take  origin 
from  the  inner  surface  of  the  sides  of  the  true  pelvis,  and,  passing 
obliquefy  downwards  and  inwards,  meet  across  the  outlet  of  that 
cavity,  so  as  together  to  form  a thin,  funnel-shaped  muscle,  which 
embraces  the  parts  descending  through  it,  and  constitutes,  as  it  were, 
a movable  floor  to  the  pelvic  cavity. 

The  origin  of  each  levator  muscle  is  most  extensive  ; and,  in  order 
to  explain  it  clearly,  it  is  necessaiy  to  advert  for  an  instant  to  the 
arrangement  of  the  fasciee  of  the  pelvis,  with  which  it  is  intimately 
connected.  The  pelvic  fascia,  in  descending  from  the  brim  of  the 
pelvis,  covers  the  upper  part  of  the  internal  obturator  muscle,  and 
may  be  traced  as  a single  fibrous  layer,  as  far  as  to  a while  line  or 
band  which  stretches  from  near  the  symphysis  pubis  to  the  spine  of 
the  ischium.  Along  this  line,  the  fascia  may  be  said  to  split  into  two 
layers:  one,  named  the  obturator  fascia,  which  continues  downwards 
over  the  remainder  of  the  internal  obturator  muscle ; and  the  other, 
called  the  recto-vesical  fascia,  which  passes  inwards  and  downwards 
towards  the  side  of  the  rectum,  bladder,  and  prostate  in  the  male,  and 
of  the  rectum  and  vagina  in  the  female. 

Now  the  levator  ani  is  situated  between  the  obturator  and  recto- 
vesical fascim,  in  close  contact,  however,  with  the  under  surface  of 
the  last-named  fascia,  immediately  beneath  which  it  forms  a broad 
and  thin  muscular  stratum.  The  greater  part  of  the  muscle  arises 
above,  from  along  the  angle  of  divergence  of  the  obturator  and  recto- 
vesical fasciae,  that  is,  from  the  under  surface  of  the  white  band  above 
mentioned  as  stretching  from  near  the  symphysis  pubis  to  the  spine  of 
the  ischium.  Besides  this  long  line  of  origin  from  the  fasciae,  the 
levator  ani  arises  behind  from  the  spine  of  the  ischium  (^),  and,  in 
front,  from  the  posterior  surface  of  the  body  and  ramus  of  the  pubes, 
near  to  the  symphysis  and  close  above  the  pubic  arch. 

From  this  extensive  origin  the  fibres  of  the  levator  proceed  down- 
wards and  inwards  towards  the  middle  line  of  the  floor  of  the  pelvis. 
Its  hindmost  fasciculi  are  inserted  upon  the  side  of  the  lower  end  of 
the  coccyx ; the  bundles  next  in  order,  anteriorly,  interlace  or  unite  in 
a median  raphe  with  the  corresponding  muscle,  in  the  interval  between 
the  coccyx  and  the  margin  of  the  anus  ; the  middle  and  larger  por- 
' tion  of  the  muscle  is  prolonged  upon  the  low'er  part  of  the  rectum, 
where  it  is  connected  with  the  fibres  of  the  internal,  but  more  particu- 
larly of  the  external  sphincter;  and,  lastly,  the  anterior  muscular 
bundles  pass  between  the  rectum  and  the  genito-urinary  passages, 
and,  descending  (in  the  male)  upon  the  side  of  the  prostate,  unite  be- 
neath the  neck  of  the  bladder,  the  prostate,  and  the  neighbouring  part 
, of  the  urethra,  with  corresponding  fibres  from  the  muscle  of  the  oppo- 
site side,  and  blend  also  with  those  of  the  external  sphincter  and  deep 
transverse  perinaeal  muscles. 


472 


DEVELOPMENT  OF  ALIMENTARY  CANAL. 


The  anterior  portion  of  the  levator  ani,  which  arises  from  the  ramus 
of  the  pubes,  close  to  the  symphysis  and  above  the  pubic  arch,  and 
also  from  the  adjacent  fasciae,  is  sometimes  separated  at  its  origin  bv 
cellular  tissue  from  the  rest  of  the  muscle.  From  this  circumstance, 
and  from  its  connexion  with  the  prostate  gland,  it  was  described  bv 
Santorini,  and  since  by  Albinus  and  Soemmerring,  as  a distinct  muscle, 
under  the  name  of  the  levator  'prostatce.  In  the  female,  the  anterior 
fibres  of  the  levator  ani  descend  upon  the  sides  of  the  vagina,  and  are 
intimately  connected  with  it. 

I'he  upper  or  pelvic  surface  of  the  levator  ani  is  in  contact  with  the 
recto-vesical  fascia,  and  with  part  of  the  pelvic  viscera.  Its  under  cr 
perinmal  surface  appears  at  the  side  of  the  external  sphincter,  in  the 
ischio-rectal  fossa,  where  it  is  covered  by  a thin  layer  of  membrane 
derived  from  the  deep  perineeal  fascia,  and  also  by  a large  quantity 
of  fat.  The  posterior  border  of  the  muscle  is  continuous  with  the 
coccygeus.  Its  anterior  border  does  not  reach  the  middle  line  in 
front,  but  leaves  between  it  and  the  corresponding  border  of  the  oppo- 
site muscle  an  interval  beneath  the  pubic  arch,  through  which  the 
genito-urinary  passages  have  their  exit  from  the  pelvis. 

The  levatores  ani  support  and  elevate  the  lower  end  of  the  rectum, 
and  also  the  bladder  and  prostate.  They  flex  and  at  the  same  time 
fix  the  coccyx. 

The  coccygeus  muscle  is  placed  deeply  on  each  side,  at  the  back 
part  of  the  outlet  of  the  pelvis,  and  assists  in  closing  that  cavity, 
behind  and  below,  by  stretching  across  from  the  spine  of  the  ischium 
to  the  sides  of  the  sacrum  and  coccyx.  This  muscle  is  connected  to, 
or  even  continuous  with,  the  posterior  part  of  the  levator  ani.  It  is 
composed  of  fleshy  and  tendinous  fibres,  forming  a thin,  flat,  and  tri- 
angular plane,  which  arises  by  its  apex  from  the  spine  of  the  ischium 
and  the  lesser  sciatic  ligament,  and  is  attached  along  its  base  to  the 
border  of  the  coccyx  and  the  lower  part  of  the  sacrum.  Its  internal 
or  pelvic  surface  assists  in  supporting  the  rectum  ; its  external  or 
under  surface  rests  on  the  front  of  the  sacrosciatic  ligaments,  and  on 
the  glutaeus  maximus  muscle. 

f The  coccygei  muscles  merely  aid  in  flexing  and  fixing  the  coccyx. 

DEVELOPMENT  OF  THE  ALIMENTARY  CANAL. 

In  the  ovum  of  the  bird,  the  mucous  layer  of  the  germinal  membrane,  which 
lies  ne.xt  to  the  yolk,  soon  comes  to  be  distinguished  into  a central  And  a peri- 
pheral part.  From  the  central  part  the  alimentary  canal  is  afterwards  formed, 
whilst  the  circumference  extends  so  as  to  enclose  the  yolk  and  form  the  yolk  sac 
or  vitelline  sac,  which  after  a time  is  drawn  through  the  umbilicus  into  the  ab- 
domen of  the  chick. 

In  mammalia  and  man,  the  origin  of  the  alimentary  canal  is  precisely  similar. 
It  commences  in  the  mucous  layer  of  the  blastoderm  in  form  of  a groove,  which 
is  soon  changed  into  a tube  at  each  end,  but  is  left  open  in  the  middle  upon  die 
ventral  aspect,  and  communicates  by  means  of  a tube,  named  the  omphalo-eiileric 
canal  or  vitelline  duct,  with  the  vitelline  sac.  This  duct  is  soon  obliterated, 
a,nd  the  vitelline  sac  becomes  the  umbilical  vesicle,  which  is  henceforth  con- 
nected with  the  embryo  only  by  a slender  elongated  pedicle  containing  the  oui- 
phalo-mesenteric  vessels,  and  is  finally  atrophied. 

The  alimentary  canal  itself  is  at  first  a straight  tube  closed  at  each  end,  and 


DEVELOPMENT  OF  ALIMENTARY  CANAL. 


473 


placed  along  the  front  of  the  vertebral  column,  to  'which  it  is  closely  attached 
above  and  below  (supposing  the  embryo  to  be  placed  in  an  erect  position),  whilst 
in  the  middle  of  its  course  it  is  connected  by  a median  membranous  fold,  or 
mdimental  mesentery.  Soon,  however,  it  advances  from  the  spine,  and  forms  a 
simple  bend  in  the  middle  of  the  body,  with  a straight  portion  at  its  upper  and 
lower  end.  The  middle  or  apex  of  the  bend  advances  to  the  umbilicus,  where  it 
is  connected  with  the  umbilical  vesicle  by  the  pedicle,  and  also  by  the  omphalo- 
mesenteric vessels,  which  pass  out  there  to  the  vesicle. 

By  the  early  appearance  of  a slight  dilatation,  which  forms  the  future  stomach, 
the  primitive  simple  tube  is  divided  into  an  upper  and  a lower  portion. 

a.  From  the  upper  portion,  besides  the  oesophagus,  which  is  formed  by  a 
gradual  elongation  of  the  part,  there  are  ultimately  developed  the  mouth,  tongue, 
and  salivary  glands,  the  pharj'nx,  larynx,  trachea,  and  lungs.  At  first  the  upper 
end  is  closed ; at  length  a wide  aperture  appears,  which  is  not  the  mouth,  properly 
so  called,  but  an  opening  upon  which  the  mouth  and  lips  are  subsequently  de- 
veloped as  superadded  parts,  commencing  after  the  eighth  or  ninth  -week. 

b.  The  dilated  portion  of  the  tube  which  forms  the  stomach  turns  over  on  its 
right  side,  so  that  the  border,  which  is  connected  to  the  vertebral  column  by  the 
membranous  fold  (or  true  mesogastrium)  comes  to  be  turned  to  the  left, — the 
position  of  the  tube  being  still  vertical,  like  the  stomach  of  some  animals.  By 
degrees  it  becomes  more  dilated,  chiefly  on  what  is  now  the  left  border  but  sub- 
sequently the  great  curvature,  and  assumes  first  an  oblique  and  finally  a trans- 
verse position,  carrying  with  it  the  mesogastrium,  from  which  the  great  omentum 
is  afterwards  produced.  The  pylorus  is  seen  at  the  third  month,  but  is  very  slightly 
marked.  Immediately  below  the  stomach,  the  duodenum  is  formed ; and  upon 
this  part  of  the  canal  commence  the  rudiments  of  the  liver,  pancreas,  and  spleen, 
the  two  former  having  protrusions  of  the  mucous  membrane  growing  into  their 
blastemic  mass. 

In  the  mean  time  the  part  below  the  stomach  becomes  the  intestinal  canal ; 
that  portion  of  it  which  is  suspended  by  a mesentery  forming  (besides  the  duo- 
denum) the  jejunum,  the  ileum,  the  ccecum,  and  the  colon,  whilst  the  lower  and 
attached  part  constitutes  the  rectum.  The  place  of  distinction  between  the  small 
and  the  large  intestine,  which  is  soon  indicated  by  the  protrusion  of  the  ccecum, 
is  at  a point  just  below  the  apex  or  middle  of  the  simple  bend  already  mentioned. 
As  the  small  intestine  grows,  the  part  below  the  duodenum  forms  a coil,  which  at 
first  lies  in  the  commencing  umbilical  cord,  but  retires  again  into  the  abdomen 
about  the  tenth  week ; afterwards  it  continues  to  elongate,  and  its  convolutions 
become  more  and  more  numerous.  The  diverticula  sometimes  found  projecting 
from  the  small  intestine  are  supposed  to  be  developed  from  a persistent  portion 
of  the  vitelline  duct,  which  continues  to  grow  with  the  rest  of  the  bowel.  The 
large  intestine  is  at  first  less  in  calibre  than  the  small.  The  development  of  the 
cfficum  and  its  appendix  has  already  been  described  (p.  465).  It  appears  as  a 
protrusion  a httle  below  the  ape.x  of  the  bend  in  the  primitive  intestinal  tube,  and, 
as  well  as  the  commencing  colon,  is  at  first  lodged  in  the  umbilicus  with  the  coil 
of  small  intestine.  The  appendix  is  at  first  of  equal  width.  The  ileo-coecal  vmlve 
appears  at  the  commencement  of  the  third  month.  When  the  coils  of  intestine 
and  coBcum  have  retired  from  the  umbilicus  into  the  abdomen,  the  colon  is  at 
first  to  the  left  of  the  convolutions  of  the  small  intestine,  but  then,  together  with 
the  meso-colon,  crosses  over  its  upper  part  at  the  junction  of  the  duodenum  and 
jejunum.  The  ccecum  and  transverse  colon  are  then  found  just  below  the  liver ; 
finally,  the  ccecum  descends  to  the  right  iliac  fossa.  At  the  fourth  or  fifth  month 
the  parts  are  in  the  same  position  as  in  the  adult. 

The  lower  straight  and  attached  portion  of  the  tube  eventually  forms  the 
rectum.  The  anal  orifice  does  not  exist  at  first,  but  appears  a week  or  so  later 
than  the  oral  opening. 

Coats  of  the  intestine. — At  a very  early  period  the  walls  of  the  intestinal  tube 
appear  to  consist  of  two  layers,  both  of  which  are  originally  composed  of  nucle- 
ated cells.  The  outer  one  is  more  transparent  than  the  other,  and  is  supposed  by 
Bischoff  to  be  metamorphosed  into  the  muscular  and  cellular  coats,  whilst  the 
inner  layer  forms  the  mucous  membrane.  The  serous  coat  is  said  to  be  developed 
afterwards  upon  the  surface  of  the  intestine,  and,  at  the  same  time,  upon  that  of 

40* 


474 


THE  LIVER. 


all  the  other  abdominal  organs,  and  on  the  walls  of  the  abdomen.  The  mucous 
membrane  is  at  lirst  very  thick,  and  is  soon  provided  with  a conspicuous  layer  of 
epithelium,  which  after  a time  accumulates  in  considerable  quantities  in  the  in- 
testinal canal.  At  first,  villous  processes  or  folds  of  various  lengths  are  formed 
throughout  the  whole  canal.  After  a time  they  disappear  in  the  stomach  and 
large  intestine,  but  remain  persistent  in  the  intermediate  portions  of  the  tube. 
According  to  Meckel,  they  are  formed  from  larger  folds,  which  become  serrated 
at  the  edge  and  divided  into  villi. 

In  the  mean  time,  the  mucous  coat  is  completed  by  the  development  of  the 
gastric  tubules,  the  foUicles  of  Lieberkuehn,  and  the  solitary  and  agminaled 
glands. 

THE  LIVER. 

The  liver  {hepar,  jecur,  fig.  246,  is  the  large  gland  which  se- 
cretes the  hile.  It  is  very  constant  in  the  animal  series,  being  found 
in  all  vertebrate,  and,  in  a more  or  less  developed  condition,  in  most 
invertebrate  tribes. 

In  the  human  subject,  it  is  situated  in  the  upper  part  of  the 
abdominal  cavity,  occupying  the  right  hypochondriac  region,  and 
extending  across  the  epigastric  region  into  a part  of  the  left  hypo- 
chondrium.  It  is  placed  immediately  beneath  the  diaphragm,  above 
the  stomach,  duodenum,  and  colon,  behind  the  cartilages  of  the  ribs, 
and  in  front  of  the  vena  cava,  aorta,  and  crura  of  the  diaphragm, 
which  latter  parts  are  interposed  between  the  gland  and  the  vertebral 
column. 

The  liver  is  a solid  organ,  of  a dull  reddish  brown  colour,  with 
frequently  a dark  purplish  tinge  along  the  margin.  It  has  an. upper 
smooth  and  convex  surface,  and  an  under  surface  (fig.  461)  which  is 
uneven  and  concave:  the  circumference,  or  border  at  which  these 
two  surfaces  meet,  is  thick  and  rounded  behind  and  to  the  right,  that 
is,  at  the  posterior  border  and  right  extrernity  of  the  liver;  but  it 
becomes  gradually  thinner  towards  the  left  and  in  front,  where  it 
forms  the  left  extremity  and  the  sharp  anterior  margin. 

The  liver  is  the  largest  gland  in  the  body,  and  by  far  the  most 
bulky  of  the  abdominal  viscera.  It  measures  about  ten  or  twelve 
inches  transversely  from  right  to  left,  between  six  and  seven  inches 
from  its  posterior  to  its  anterior  border,  and  about  three  inches  from 
above  downwards  at  its  thickest  part,  which  is  towards  the  right  and 
posterior  portion  of  the  gland.  The  average  bulk  of  the  liver,  ac- 
cording to  Krause,  is  eighty-eight  cubic  inches.  Its  ordinary  weight 
in  the  adult  is  stated  to  be  between  three  and  four  pounds,  or  more 
nearly  from  fifty  to  sixty  ounces  avoirdupois. 

According  to  the  facts  recorded  by  Dr.  John  Reid,*  it  weighed,  in  43  cases  out 
of  82,  between  48  and  58  ounces  in  the  adult  male  ; and  in  17  cases  out  of  36, 
its  weight  in  the  adult  female  ranged  between  40  and  50  ounces.  It  is  generally 
estimated  to  be  equal  to  about  l-36th  of  the  weight  of  the  whole  body;  but  in  the 
foetus,  and  in  early  life  its  proportionate  weight  is  greater. 

The  specific  gravity  of  the  liver,  according  to  Krause  and  others, 
is  between  1-05  and  D06:  in  fatty  degeneration  this  is  reduced  to 
1-03,  or  even  less. 

* Lond.  and  Edin.  Monthly  Journal  of  Med.  Science,  April,  1843. 


FORM  OF  LIVER. 


475 


The  form,  position,  and  connexions  of  the  surfaces  and  borders  of 
the  Liver. — The  upper  convex  surface,  free,  smooth,  and  covered  by 
peritoneum,  is  accurately  adapted  to  the  vault  of  the  diaphragm 
above,  and  is  covered,  to  a small  extent  in  front,  by  the  abdominal 
parietes.  The  line  of  attachment  of  a fold  of  peritoneum,  named  the 
broad  ligament  of  the  liver,  marks  off  this  surface  unequally  into  a 
right  and  a left  portion.  The  right  portion  is  much  larger  and  more 
convex  than  the  left,  and  reaches  higher  beneath  the  ribs,  corre- 
sponding thus  with  the  elevated  position  of  the  diaphragm  on  that 
side.  By  means  of  the  diaphragm,  the  liver  is  separated  from  the 
concave  base  of  the  right  lung,  the  thin  margin  of  which  descends  so 
as  to  intervene  between  the  surface  of  the  body  and  the  solid  mass  of 
the  liver — a fact  well  known  to  the  auscultator. 

The  convex  surface  of  the  liver  is  protected,  on  the  right,  by  the  six 
or  seven  lower  ribs,  and  in  front  by  the  cartilages  of  the  same  and  by 
the  ensiform  cartilage — the  diaphragm,  of  course,  being  interposed. 
Being  suspended  by  ligaments  to  the  diaphragm  above,  and  supported 
below,  in  common  with  the  rest  of  the  viscera,  by  the  abdominal 
muscles,  the  situation  of  the  liver  is  modified  by  the  position  of  the 
body,  and  also  by  the  movements  of  respiration  : thus,  in  the  upright 
or  sitting  posture,  the  liver  reaches  below  the  marjjin  of  the  thorax  ; 
but  in  the  recumbent  position,  the  gland  ascends  an  inch  or  an  inch 
and  a half  higher  up,  and  is  entirely  covered  by  the  ribs,  except  a 
small  portion  opposite  the  siibsternal  notch.  Again,  during  a deep 
inspiration,  the  liver  descends  below  the  ribs,  and  in  expiration  retires 
behind  them.  In  females  the  liver  is  often  permanently  forced  down- 
wards below  the  costal  cartilages,  owing  to  the  use  of  light  stays : 
sometimes  it  reaches  nearly  as  low  as  the  crest  of  the  ilium ; and,  in 
many  cases,  its  convex  surface  is  indented  from  the  pressure  of  the 
ribs  upon  it. 

The  under  or  concave  surface  of  the  liver,  (fig.  461,)  which  is 
directed  downwards  and  backwards,  is  uneven.  Besides  several 
depressions  found  at  its  points  of  contact  with  other  organs,  as  the 
stomach,  colon,  and  kidneys,  it  presents  certain  divisions  or  lobes,  and 
several  fissures,  to  be  presently  described.  The  greater  part  of  this 
surface  is  free  and  covered  by  the  peritoneum  ; but  this  is  not  the  case 
where  the  large  vessels  enter  the  gland,  nor  where  it  is  attached  by 
cellular  tissue  to  adjacent  parts.  It  is  separated  into  two  unequal 
parts,  one  right  (*)  and  the  other  left  (®),  by  a longitudinal  or  antero- 
posterior fissure  (®).  The  part  to  the  left  of  this  fissure  is  supported 
on  the  pyloric  extremity  and  anterior  surface  of  the  stomach,  on 
which  it  moves  freely.  (See  fig.  473,  in  which  the  liver  is  represented 
as  turned  upwards,  w'ith  the  stomach.)  When  the  stomach  is  quite 
empty,  the  left  part  of  this  surface  of  the  liver  may  overlap  the  cardiac 
end  of  that  viscus.  To  the  right  of  the  longitudinal  fissure  the  liver 
rests  and  moves  freely  upon  the  first  part  of  the  duodenum,  and  upon 
the  hepatic  flexure  of  the  colon,  at  the  juncture  of  the  ascending  and 
transverse  portions  of  that  intestine.  Further  back  it  is  in  contact 
with  the  fore  part  of  the  right  kidney  and  suprarenal  capsule,  for 
which  it  presents  one  or  two  corresponding  depressions.  The  gall- 


476 


LOBES  OF  LIVER, 


bladder  is  also  attached  to  this  right  portion  of  the  under  surface  of 
the  liver  by  peritoneum,  loose  cellular  tissue,  and  vessels. 

The  anterior  border  of  the  liver,  a thin,  free,  and  sharp  margin,  is 
the  most  movable  part  of  the  gland.  Opposite  the  longitudinal  fissure 
and  the  line  of  attachment  of  the  broad  ligament,  this  anterior  bor- 
der presents  a notch  (^®),  which  separates  the  right  and  left  lobes  of  the 
liver,  and  lodges  the  round  ligament.  To  the  right  of  this  notch  there 
is  often  another  slight  one  opposite  the  fundus  of  the  gall-bladder  (*'’). 

The  posterior  border  of  the  liver,  which  is  directed  backwards  and 
upwards,  is  thick  and  rounded  on  the  right  side,  but  becomes  gradually 
thinner  towards  the  left.  It  is  the  most  fixed  part  of  the  organ,  and  is 
firmly  attached  by  cellular  tissue  to  the  diaphragm,,  the  peritoneum 
being  here  reflected  away  from  the  liver  on  to  the  diaphragm,  so  as  to 
form  the  coronary  ligament.  This  border  of  the  liver  is  curved  oppo- 
site to  the  projection  of  the  vertebral  column,  and  has  a deep  groove 
for  the  reception  of  the  ascending  vena  cava. 

Of  the  two  extremities  of  the  liver,  the  right  is  placed  lower  down, 
and  is  thick  and  obtuse;  whilst  the  left  is  the  thinnest  part  of  the  gland, 
and  ascends  to  a higher  level,  reaching  across  to  the  cardiac  end  of 
the  stomach.  Both  extremities  are  attached  to  the  diaphragm  by 
peritoneal  folds,  named  the  lateral  ligaments. 

Besides  being  attached  to  large  blood-vessels,  and  supported  by  the 
parts  beneath  and  by  the  abdominal  muscles,  the  liver  is  suspended  by 
its  ligaments,  which  are  five  in  number. 

The  Ligaments. — These  are  five  in  number,  and,  with  one  exception 
(the  ligamentum  teres),  are  formed  merely  by  folds  of  the  peritoneum. 
1.  The  broad,  falciform,  or  suspensory  ligament  is  a wide  thin  mem- 
brane, composed  of  two  layers  of  peritoneum,  closely  united  together. 
By  one  of  its  margins  it  is  connected  with  the  under  surface  of  the 
diaphragm,  and  with  the  posterior  surface  of  the  sheath  of  the  right 
rectus  muscle  of  the  abdomen,  as  low  as,  the  umbilicus;  and  by  another 
it  is  attached  along  the  convex  surface  of  the  liver,  from  its  posterior 
border  to  the  notch  in  its  anterior  border.  The  remaining  margin  of 
the  ligament  is  free,  and  contains  between  its  layers  the  round  liga- 
ment. 2.  The  round  ligament  (ligamentum  teres)  is  a dense  fibrous 
cord,  which  ascends  from  the  umbilicus,  within  the  lower  edge  of  the 
broad  ligament,  towards  the  notch  in  the  anterior  border  of  the  liver, 
and  there  enters  the  longitudinal  fissure  on  the  under  surface.  It  i.s 
the  remains  of  the  umbilical  vein  of  the  foetus.  3.  The  coronary  liga- 
ment is  formed  by  the  reflection  of  the  peritoneum  from  the  diaphragm 
to  the  posterior  border  of  the  liver.  In  this  situation  there  is  a broad 
triangular  portion  of  the  gland,  which  is  attached  by  firm  cellular 
tissue  to  the  diaphragm,  and  the  surrounding  reflection  of  the  peri- 
toneal membrane  constitutes  the  coronary  ligament.  4 and  5.  Bo'h 
on  the  right  and  the  left  end  of  the  liver  the  peritoneum  also  forms  a 
triangular  reflection,  extending  to  the  adjacent  part  of  the  diaphragm 
these  are  the  right  and  left  lateral  or  triangular  ligaments,  of  which 
the  left  is  longer  and  more  distinct  than  the  other. 

The  Lobes. — The  lobes  of  the  liver,  like  the  ligaments,  are  five  in 


FISSURES  OF  LIVER. 


477 


number;  and,  indeed,  ana- 
tomists have  endeavoured 
to  trace  the  number  five 
in  respect  also  of  the  fis- 
sures and  vessels  of  the 
gland.  The  lobes  are 
named  the  right  and  the 
left,  the  lobe  of  Spigelius, 
the  caudate  or  tailed  lobe, 
and  the  square  lobe.  1, 
2.  The  right  and  left  lobes 
(fig.  461,^  f)  are  separated 
from  each  other  on  the 
under  surface  by  the  lon- 
gitudinal fissure  (®),  and 
in  front  by  the  interlobular 
notch : on  the  convex  sur- 
face of  the  liver  there  is 
no  other  indication  of  a 
separation  between  them 
than  the  line  of  attach- 
ment of  the  broad  liga- 
ment. The  right  lobe  is 
of  a long  square  form  ; it 
is  much  larger  and  thicker 


[Fig.  461. 


The  under  surface  of  the  liver.  1.  The  right  lobe.  2. 
The  left  lobe.  3.  The  lobus  quadrates.  4.  The  lobus 
Spigelii.  5.  The  lobus  caudatus.  6.  The  longitudinal 
fissure;  the  numeral  is  placed  on  the  rounded  cord,  the 
remains  of  the  umbilical  vein.  7.  The  pons  hepatis.  8. 
The  fissure  for  the  ductus  venosus ; the  obliterated  cord  of 
tbe  ductus  is  seen  passing  backwards  to  be  attached  to  the 
coals  of  the  inferior  vena  cava  (9).  10.  The  gall-bladder 

lodged  in  its  fossa.  II.  The  transverse  fissure,  containing, 
from  before  backwards,  the  hepatic  duct,  hepatic  artery, 
and  portal  vein.  12.  The  vena  cava.  13.  A depression 
corresponding  with  the  curve  of  the  colon.  14.  A double 
depression  produced  by  the  right  kidney  and  its  supra-renal 
capsule.  15.  The  rough  surface  on  the  posterior  border  of 
the  liver  left  uncovered  by  peritoneum;  the  cut  edge  of 
peritoneum  surrounding  this  surface  forms  part  of  the  coro- 
nary ligament.  16.  The  notch  on  the  anterior  border,  sepa- 
rating the  two  lobes.  17.  The  notch  on  the  posterior  bor- 
der, corresponding  with  the  vertebral  column. — W]. 


than  the  left,  which  is 
nearly  triangular  in  out- 
line, and  constitutes  only 
about  one-fifth  or  one-sixth  of  the  entire  gland.  3,  4,  5.  The  other 
three  lobes  are  small,  and  might  be  said  to  form  a part  of  the  right 
lobe,  on  the  under  surface  of  which  they  are  situated.  The  Spigelian 
lobe  lobulus  Spigelii)  projects  in  the  form  of  a pyramidal  mass  from 
the  middle  of  the  back  part  of  the  liver,  and  is  bounded  by  three 
large  fissures,  to  be  immediately  described,  which  , lodge  the  vena 
portae,  the  vena  cava,  and  the  remains  of  the  ductus  venosus.  The 
caudate  or  tailed  lobe  (®)  is  a sort  of  ridge  which  extends  from  the 
base  of  the  Spigelian  lobe  to  the  under  surface  of  the  right  lobe.  This, 
in  the  natural  position  of  the  parts,  passes  forwards  above  the  foramen 
of  Winslow,  the  Spigelian  lobe  itself  being  situated  behind  the  small 
omentum,  and  projecting  into  the  omental  sac.  The  square  lobe  (% 
lobulus  anonymus,  lobulus  quadratus)  is  that  part  which  is  situated 
between  the  gall-bladder  and  the  great  longitudinal  fissure,  and  in 
front  of  the  fissure  for  the  portal  vein. 

The  Fissures. — Of  the  five  fissures  or  fosscB  of  the  liver,  which  are 
seen  on  its  under  surface  only,  all  are  not  of  equal  significance.  1. 
The  transverse  fissure,  or  portal  fissure  ('^),  is  the  most  important, 
because  it  is  here  that  the  great  vessels  and  nerves  enter,  and  the 
hepatic  duct  passes  out.  It  is  situated  across  the  middle  of  the  right 
lobe,  somewhat  nearer  to  its  posterior  than  its  anterior  border,  occu- 
pying its  inner  half  only,  and  meeting  nearly  at  right  angles  with  the 


478 


VESSELS  OF  LIVER. 


longitudinal  fissure.  It  is  bounded  in  front  by  the  square  lobe  (s),  and 
behind  by  the  Spigelian  lobe  ('‘)  and  the  caudate  lobe  (®).  These 
boundaries  were  compared  to  the  pillars  of  a gate,  the  fissure  itself 
being  likened  to  a gateway,  ; and  hence  the  large  vein  to  which 
it  gives  admission  was  named  vena  portce,  or  vena  portarum.  Besides 
this  vessel,  the  hepatic  artery  and  nerves  and  the  hepatic  duct  and 
principal  lymphatics  enter  or  pass  out  at  the  transverse  fissure,  which 
has  therefore  been  termed  the  hiliis  of  the  liver.  2,  3.  The  longitudinal 
fissure,  which  separates  the  right  and  left  lobes  of  the  liver  from  each 
other,  is  divided  into  two  parts  by  its  meeting  with  the  transverse 
fissure.  The  anterior  part,  named  the  umbilical  fissure,  contains 
the  umbilical  vein  in  the  foetus,  and  the  remains  of  that  vein  in  the 
adult,  which  then  constitutes  the  round  ligament.  It  is  situated  between 
the  square  lobe  and  the  left  lobe  of  the  liver,  the  substance  of  which 
often  forms  a bridge  (’’)  across  the  fissure,  so  as  to  convert  it  partially  or 
completely  into  a canal.  The  posterior  part  (**)  is  named  the  fissure 
of  the  ductus  venosus  (fossa  ductus  venosi) ; it  continues  the  umbilical 
fissure  backwards  between  the  lobe  of  Spigelius  and  the  left  lobe ; and 
it  lodges  the  ductus  venosus  in  the  foetus,  and  in  the  adult  a slender 
cord  or  ligament  into  which  that  vein  is  converted.  4.  The  fissure 
or  fossa  of  the  vena  cava  is  situated  at  the  back  part  of  the  liver, 
betw'een  the  Spigelian  lobe  on  the  left  and  the  right  lobe  on  the  righi, 
separated  from  the  transverse  fissure  by  the  caudate  lobe.  It  is  con- 
tinued upwards  in  an  oblique  direction  on  to  the  posterior  border  of 
the  liver,  and  may  almost  be  said  to  join  behind  the  Spigelian  lobe 
with  the  fissure  for  the  ductus  venosus.  It  is  at  the  bottom  of  this 
fossa  that  the  blood  leaves  the  liver  by  the  hepatic  veins,  which  end 
here  in  the  vena  cava.  The  sdbstance  of  the  liver  in  some  cases 
unites  around  the  vena  cava,  and  encloses  that  vessel  in  a canal.  5. 
The  last  remaining  fissure,  or  rather, /ossa,  (fossa  cystis  fellese,)  is  that 
for  the  lodgment  of  the  gall-bladder  (^“) : it  is  sometimes  continued 

into  a slight  notch  on  the  anterior  margin  of  the  liver. 

® ^..11 

Besides  these,  there  are  two  shallow'  impressions  on  the  under  sur- 
face of  the  right  lobe : one  in  front  {impressio  colica),  (^^)  corresponding 
with  the  hepatic  flexure  of  the  colon ; and  one  behind  {impressio  re- 
nalis),  (’^)  corresponding  with  the  right  kidney. 

Vessels  and  Ducts. — 1,  2.  The  two  vessels  by  which  the  liver  is 
supplied  with  blood  are  the  hepatic  artery  and  the  vena  portm.  The 
hepatic  artery,  (fig.  246,  d,)  a branch  of  the  cceliac  axis,  is  interme- 
diate in  size  between  the  other  two  branches  of  that  trunk,  being 
larger  than  the  coronary  artery  of  the  stomach,  but  not  so  large  fis 
the  splenic  artery.  It  is,  therefore,  a small  vessel  in  comparison  with 
the  size  of  the  organ  to  which  it  is  distributed.  It  enters  the  trans- 
verse fissure,  and  there  divides  into  a right  and  left  branch,  for  the 
two  principal  lobes  of  the  liver.  Sometimes  there  is  an  hepatic 
branch,  derived  from  the  coronary  artery  of  the  stomach  or  from  the 
superior  mesenteric.  The  coats  of  the  liver  also  receive  small  vessels 
from  other  sources,  as  from  the  branches  of  the  phrenic,  internal 
mammary,  and  epigastric  arteries. 

By  far  the  greater  part  of  the  blood  which  passes  through  the  liver. 


STRUCTURE  OF  LIVER. 


479 


— and  this  is  its  chief  peculiarity  as  a gland, — is  conveyed  to  it  by  a 
large  vein,  the  vena  portce  (fig.  263,  a).  This  vein  is  formed  by  the 
union  of  nearly  all  the  veins  of  the  chylopoietic  viscera,  viz.,  those 
from  the  stomach  and  intestines,  the  pancreas  and  spleen,  omentum 
and  mesentery,  and  those  from  the  gall-bladder  also.  It  enters  the 
porta,  or  transverse  fissure,  where,  like  the  hepatic  artery,  it  divides 
into  two  principal  branches. 

3.  The  bile-duct  or  hepatic  duct  is,  also,  formed  by  the  union  of  a 
right  and  left  branch,  which  issue  from  the  bottom  of  the  transverse 
fissure,  and  soon  unite  at  a very  obtuse  angle.  (Figs.  263  and  473.) 

The  three  vessels  'above  mentioned  ascend  to  the  liver  between  the 
layers  of  the  gastro-hepatic  omentum,  above  the  foramen  of  Winslow, 
and  thus  reach  the  transverse  fissure  together.  Their  relative  position 
is  as  follows : — The  bile-duct  is  to  the  right,  the  hepatic  artery  to  the 
left,  and  the  large  portal  vein  is  behind  and  between  the  other  two. 
They  are  accompanied  by  numerous  lymphatic  vessels  and  nerves, 
and  are  surrounded  by  a cellular  tissue  named  the  capsule  of  Glisson. 
The  branches  of  these  three  vessels  accompany  one  another  in  their 
course  through  the  liver  nearly  to  their  termination  ; and  in  this  course 
are  surrounded  by  a common  investment  (Glisson’s  capsule),  which  is 
prolonged  into  the  interior  of  the  organ. 

4.  The  hepatic  veins,  which  convey  the  blood  out  from  the  liver, 
pursue  an  entirely  different  and  independent  course  through  its  sub- 
stance, and  pass  out  at  its  posterior  border,  where,  at  the  bottom  of 
the  fossa  already  described,  they  end  by  two  principal  branches,  be- 
sides other  smaller  ones,  in  the  vena  cava. 

5.  The  last  order  of  vessels  belonging  to  the  liver  are  the  lym- 
phatics. They  are  large  and  numerous,  and  form  a deep  and  a 
superficial  set.  The  deep  lymphatics  accompany  the  vessels  in  the 
portal  canals,  to  be  presently  described,  and  emerge  at  the  transverse 
fissure.  The  superficial  set  form  a network  on  the  upper  and  under 
surfaces  of  the  organ,  and  communicate  freely  with  each  other  and 
also  with  the  deep  set. 

, Nerves. — The  nerves  of  the  liver  are  derived  partly  from  the  coeliac 
plexus,  and  partly  from  the  pneumogastric  nerves,  especially  from  the 
left  pneumogastric.  They  enter  the  liver  supported  by  the  hepatic 
artery  and  its  branches ; along  with  which  they  may  be  traced  a 
considerable  way  in  the  portal  canals,  but  their  ultimate  distribution 
is  not  known. 

Structure  of  the  Liver. 

Coats. — The  liver  has  two  coverings,  viz.,  a serous  coat  and  a 
proper  cellular  coat.  The  serous  coat,  smooth,  moist,  shining,  and 
transparent,  is  derived  from  the  peritoneum,  and  covers  every  part  of 
the  free  surface  of  the  gland;  but  it  is  deficient  at  the  part  of  the  liver 
round  which  the  suspensory,  coronary,  and  two  lateral  ligaments  are 
reflected  to  the  diaphragm,  and  also  at  the  bottom  of  the  several 
fissures  or  fossae,  especially  those  for  the  vena  portae,  vena  cava,  and 
gall-bladder.  It  adheres  closely  to  the  proper  or  cellular  coat. 

The  cellular  or  fibrous  coat,  as  it  is  also  called,  invests  the  whole 


480 


LOBULES  OF  LIVER. 


gland.  Opposite  to  the  parts  covered  by  ihe  serous  coat  it  is  thin 
and  difficult  to  demonstrate;  but  vi'here  the  peritoneal  coat  is  absent, 
as  at  the  posterior  border  of  the  liver,  and  in  the  portal  fissure,  it  is 
denser  and  more  evident.  Its  inner  surface  is  attached  to  the  hepatic 
glandular  substance,  being  there  continuous  with  the  delicate  cellular 
tissue  between  the  lobules  of  which  the  gland  is  composed.  At  the 
transverse  fissure  it  becomes  continuous  with  the  capsule  of  Glisson. 

The  proper  substance  of  the  liver,  which  has  a reddish  brown 
colour  and  a mottled  aspect,  is  compact,  but  not  very  firm.  It  is 
easily  cut  or  lacerated,  and  is  not  unfrequently  ruptured  during  life 
from  accidents,  in  which  other  parts  of  the  body  have  escaped  injury, 
When  the  substance  of  the  liver  is  torn,  the  broken  surface  is  not 
smooth  but  minutely  granular,  and  this  is  owing  to  the  fact  of  its 
being  composed  of  a multitude  of  small  masses  called  lobules  (fig.  402). 
These  lobules  vary  from  half  a line  to  nearly  a line  in  diameter; 
they  are  closely  packed  polyhedral  bodies,  about  the  size  of  a pin’s 
head,  which  are  held  together  by  fine  cellular  tissue,  and  by  the  blood- 
vessels and  ducts.  This  inter- 
Fig-.  462.  lobular  tissue  is  continuous  with 

the  fibrous  coat  on  the  exterior 
of  the  liver,  and  also  with  the 
capsule  of  Glisson  within  the 
portal  canals.  Such,  at  least, 
are  the  views  entertained  b\? 
Mr.  Kiernan.*  Some  anato- 
mists of  authority,  as  W eber  and 
Krukenberg,  while  they  admit 
the  existence  of  fissures  between 
the  lobules  to  give  passage  to 
the  vessels,  deny  that  the  lobules 
are  completely  insulated,  be- 
lieving that  they  coalesce  at  dif- 
ferent points.  After  a second 
investigation  of  this  point,  Mul- 
ler still  adheres  to  the  opinion  of 
Mr.  Kiernan.f  On  the  surface 
of  the  liver  the  lobules  are  trian- 
gular, and  more  or  less  flattened 
on  their  exposed  surface;  but 
deeper  within  the  substance  of 

H,  longitudinal  section  of  an  hepatic  vein ; a,  a,  gland,  they  have  usually  four 

Eortions  of  the  canal  from  which  the  vein  has  g . , rpi  „ „„„  „|| 

een  removed ; h.b,  orifices  of  intralobular  veins.  Of  tive  SlueS.  1 hey  are  all 
The  large  onhces  opening  into  the  hepatic  vein  are  compactlv  arranged  arOUnd  the 
the  mouths  oflhesublobular  veins.  (Af.er  Kiernan.)  branches  of  ihe 


hepatic  veins  (H),  each  lobule  resting  by  a smooth  surface,  or  base, 
upon  the  vein,  and  being  connected  with  it  by  a small  venous  trunk 
{b),  which  arises  in  the  centre  of  the  lobule,  and  passes  out  from 
the  middle  of  its  base  to  end  in  the  larger  subjacent  vessel.  The 


Philosoph.  Transactions,  1833,  vol.  ii. 


t Archiv,  1843, 


HEPATIC  VEINS. 


481 


small  veins  proceeding  from  the  centre  of  the  lobules  are  named  the 
intralobular  veins  (b)  and  those  on  which  the  lobules  rest,  the  sub- 
lobular  veins.  If  one  of  these  sublobular  veins  be  opened,  the 
bases  of  the  lobules  {b)  may  be  seen  through  the  coats  of  the  vein, 
which  are  here  very  thin,  forming  a tessellated  appearance,  each  little 
polygonal  space  representing  the  base  of  a lobule,  and  having  in  its 
centre  a small  spot,  which  is  the  mouth  of  the  intralobular  vein. 
When  divided  in  the  direction  of  a sublobular  vein,  the  attached 
lobules  present  a foliated  appearance,  for  that  part  of  their  surface 
which  is  not  in  contact  with  the  vein  is  itself  slightly  lobulated  or 
developed  into  blunt  processes.  Cut  in  a transverse  direction,  they 
present  a polyhedral  form.  (Fig.  463.) 

The  hepatic  veins,  which  may  now  be  traced,  commence  in  the 
centre  of  each  lobule  by  the  union  of  its  capillary  vessels  into  a single 
independent  intralobular  vein.  (Fig.  464,b)  These  minute  intra- 
lobular veins,  (fig.  462,  b)  open  at  once  into  the  sides  of  the  sub- 
jacent sublobular  veins.  The  sublobular  veins  are  of  various  sizes, 
and  anastomose  together.  Uniting  into  larger  and  larger  vessels,  they 
end  at  length  in  another  kind  of  hepatic  venous  trunks  (H),  which 
receive  no  intralobular  veins.  Lastly,  these  venous  trunks,  con- 
verging towards  the  posterior  border  of  the  liver,  and  receiving  in 
their  course  other  small  sublobular  veins,  terminate  in  the  vena  cava, 
at  the  bottom  of  the  fossa  already  described.  In  this  course,  the 
hepatic  veins  and  their  successive  ramifications  are  unaccompanied 
by  any  other  vessel.  Their 
coats  are  extremely  thin  ; the 
sublobular  branches  adhere  im- 
mediately to  the  lobules,  and 
even  the  larger  trunks  have  but 
a very  slight  cellular  invest- 
ment, which  connects  them  to 
the  substance  of  the  liver. 

Hence  the  divided  ends  of  these 
veins  are  seen  upon  a section 
of  the  liver  as  simple  open  ori- 
fices, sui'rounded  closely  by  the 
solid  substance  of  the  gland 
{a,  a). 

2.  The  vena  portae  and  hepatic 
artery, which, together  with  the 
biliary  ducts,  enter  the  liver  at 
the  transverse  fissure,  have  a 
totally  different  course,  ar- 
rangement, and  distribution 
from  those  of  the  hepatic  vein. 

Within  the  liver  the  branches 
of  these  three  vessels  lie  to- 
gether in  certain  canals,  called 
portal  canals,  which  are  tubu- 
lar passages  formed  in  the 

VOL,  II. 


Section  of  a portal  canal  and  portal  vein  lying  in 
if,  in  company  with  the  hepatic  artery  and  duct. 
(Kiernan.)  p.  Branch  of  vena  portiB,  situated  in  o,  a, 
a portal  canal,  formed  amongst  the  lobules  of  the  liver. 
The  large  orifices  opening  into  the  portal  vein  are  the 
mouths  of  the  vaginal  branches,  h.  Orifices  of  inter- 
lobular veins  arising  at  once  from  the  large  vein.  A. 
Hepatic  artery.  D.  Hepatic  duct. 

41 


482 


HEPATIC  ARTERY  AND  DUCT. 


substance  of  the  gland,  commencing  at  the  transverse  fissure,  and 
branching  upwards  from  that  part  in  all  directions.  Each  portal  canal 
(even  the  smallest)  contains,  as  shown  in  a longitudinal  section  (fig. 
4(53),  one  principal  branch  of  the  vena  portae  (p),  of  the  hepatic  artery 
(a),  and  of  the  biliary  duct  (d);  the  whole  being  invested  by  the  con- 
tinuation, along  the  canals,  of  the  cellular  sheath  named  Glisson’s 
capsule.  This  arrangement  of  the  parts  is  rendered  evident  by  mak- 
ing a cross  section  of  a portal  canal,  when  the  large  orifice  of  the 
portal  vein,  accompanied  by  the  biliary  duct  (of  much  smaller  size) 
and  a branch  of  the  hepatic  artery,  which  is  the  smallest  of  the  three, 
are  seen,  surrounded  by  a web  of  cellular  tissue,  which  separates  them 
from  the  substance  of  the  liver. 

The  portal  veins  (p),  as  they  lie  in  the  portal  canals,  give  offlatera! 
branches,  named  vaginal  veins,  which  ramify  and  form  a plexus  in 
Glisson’s  capsule,  and  then  send  off  smaller  branches,  called  inter- 
lobular veins,  which  enter  between  the  lobules  (fig.  464,  ^ ^),  and,  after 
ramifying  freely,  and,  according  to  Kiernan,  anastomosing,  penetrate 
the  surface  of  the  lobules  themselves,  and  end  in  a capillary  network 
within  them.  From  this  network  the  intralobular  (hepatic)  vein  of 
each  lobule  (‘)  takes  its  origin.  In  the  smaller  portal  canals  the 
vaginal  veins  and  plexuses  are  less  evident,  for  many  of  the  intralo- 
bular veins  (as  at  b,  fig.  463)  arise  at  once  from  the  principal  branch 
(p)  of  the  vena  portae.  In  the  smaller  canals,  too,  the  capsule  of  Glis- 
son  is  very  thin,  as  if  its  office  were  no  longer  needed  ; for  (like  the 
periosteum  and  pia  mater)  it  seems  principally  to  be  required  as  a 
tissue  in  which  the  vessels  may  divide  into  smaller  branches  before 
they  enter  the  structure  which  they  have  to  supply. 

The  hepatic  artery  (a)  also  gives  off  its  vaginal  and  interlobular 
branches.  These  are  distributed  to  the  coats  of  the  various  vessels, 
(especially  to  the  ducts,  which  become  very  red  in  a successful  injec- 
tion,) to  the  capsule  of  Glisson,  the  interlobular  cellular  tissue,  and  the 
proper  coat  of  the  liver  {rami  vasculares,  rami  capsulares).  There 
are  but  few  of  its  branches  between  the  lobules,  and  still  fewer  have 
been  found  within  their  margin.  Kiernan  believes  that  the  branches 
of  the  hepatic  artery  terminate  in  a system  of  capillary  vessels,  from 
which  the  blood  is  collected  and  conveyed  into  the  portal  veins,  by 
means  of  small  venous  radicles,  which  may  be  considered  as  intra- 
hepatic  tributary  branches  of  the  vena  portae,  analogous  to  the  supe- 
rior mesenteric,  the  splenic,  the  cystic,  and  other  extra-hepatic 
branches  or  roots  of  that  great  vein.  The  blood  from  the  hepatic 
artery,  therefore,  reaches  the  hepatic  veins  only  indirectly  through  the 
intervention  of  the  vena  portae. 

This  opinion,  which  was  also  that  of  Ferrein,*  and  is  now  supported 
by  Theile,f  is  opposed  to  the  view  that  the  hepatic  artery  and  vena  ; 
portae  communicate  by  means  of  a common  capillary  system,  with  the  j 
hepatic  veins, — an  opinion  still  maintained  by  several  anatomists  of 
authority. 

* Ferrein,  M6m.  de  I’Acad.  des  Sciences,  173.3. 

t Theile,  Hand-Worterbuch  der  Physiologie,  (Wagner’s,)  p.  342. 


STRUCTURE  OF  LOBULES. 


483 


The  branches  of  the  hepatic  ducts  (D)  have  been  traced  emerging 
from  the  surface  of  the  lobules  (®,  fig.  465),  and  forming  between  them 
an  interlobular  plexus  of  ducts.  Branches  from  this  plexus  enter  the 
portal  canals  as  vaginal  branches,  and  there  unite  into  larger  and 
larger  ducts,  which  do  not  anastomose.  There  is  always  one  princi- 
pal duct  in  each  portal  canal. 

Structure  of  the  Lobules. — From  what  has  preceded,  the  arrange- 
ment of  the  blood-vessels  within  each  lobule  will  be  readily  under- 
stood. The  ultimate  branches  of  the  vena  port®  (fig.  464,  s,  -,) 
having  ramified  upon  the  surface  of  a lobule,  enter  it  at  all  points,  and 
form  a plexus  within  it,  composed  of  radiating  and  transverse  con- 
necting vessels.  These  having  become  reduced  by  division  and  sub- 
division to  a capillary  size,  form  a netwmrk  from  which  arise  the 
commencing  radicles  of  the  intralobular  hepatic  vein  in  the  centre  (‘). 


Fig.  464.  Fig.  465. 


Fig.  464.  Diagram  showing  the  arrangement  of  the  blood-vessels  within  and  between  the 
I lobules.  (Kiernan.)  2,  2.  Interlobular  branches  of  portal  vein,  forming  the  intralobular  venous 
I plexus,  connecting  the  portal  veins  (2,  2)  with  the  intralobular  vein  (1)  in  the  centre,  which  is  the 


commencing  branch  of  the  hepatic  vein. 

! Fig.  465.  2,  2.  Branches  of  the  hepatic  duct,  which  is  supposed  to  commence  in  a ple.xus 
1 situated  towards  the  circumference  of  the  lobule  called  by  Kiernan  the  biliary  plexus.  Within  this 

■ is  seen  the  central  part  of  the  lobule,  containing  branches  of  the  intralobular  (hepatic)  vein  (1). 

; As  already  stated,  opinions  are  still  divided  as  to  the  relations  of  the 
I capillaries  of  the  hepatic  artery  to  the  capillary  network  within  the 
1 lobules.  From  the  ultimate  distribution  of  the  branches  of  the  vena 

■ port®,  it  is  evident  that  the  blood  of  that  vessel  is  largely  concerned 
1 in  the  secretion  of  the  bile.  The  hepatic  artery,  on  the  other  hand,  is 
I essentially  the  nutrient  vessel  of  the  constituent  parts  of  the  gland,  and 
‘ its  blood  either  previously  enters  the  portal  system  as  suggested  by 
] Kiernan,  and  thus  as  portal  blood  assists  in  the  secretion  of  the  bile, 
\ or,  as  supposed  by  others,  it  reaches  the  capillary  system  of  the  lobules 
i in  the  condition  of  arterial  blood. 

.rhe  distribution  of  the  portal  and  hepatic  veins  within  the  lobules,  as  just 
j described,  has  suggested  an  e.xplanation  of  the  mottled  aspect  of  the  liver,  an 
I appearance  which  has  led  to  the  erroneous  idea  of  there  being  two  substances 
I in  each  lobule,  one  darker  than  the  other.  The  colour  of  the  hepatic  substance 
? is  pale  yellow,  and  would  be  uniform  throughout,  were  it  not  varied  according 


484 


COMMENCEMENT  OF  DUCTS. 


to  the  quantity  of  blood  contained  in  its  different  vessels.  Thus,  if  the  system  of 
hepatic  veins  be  congested,  the  centre  of  each  lobule  is  dark,  and  its  margin 
pale ; this  is  the  common  case  after  death,  and  is  named  by  Mr.  Kiernan  passive 
congestion.  In  what  is  considered  an  active  state  of  hepatic  congestion,  the  dark 
colour  e.xtends  to  the  portal  system,  across  the  interlobular  fissures,  leaving  inter- 
mediate spaces,  which  remain  as  irregular  pale  spots : this  state  occurs  especially 
in  diseases  of  the  heart.  When,  on  the  other  hand,  the  portal  system  is  con- 
gested, which  is  rare,  and  occurs  generally  in  children,  the  margins  of  the  lobules 
are  dark,  and  their  centres  pale. 

The  interstices  between  the  blood-vessels  in  each  lobule  are  occu- 
pied by  the  commencement  of  the  biliary  ducts,  and  they  also  contain 
a peculiar  substance  (tlie  hepatic  substance),  composed  of  numerous 
microscopic  nucleated  corpuscles.  These  corpuscles  present  specific 
characters  ; they  are  evidently  concerned  in  the  secretion  of  the  bile, 
and  are  named  the  hepatic  cells  or  corpuscles. 

Ducts. — According  to  Mr.  Kiernan  the  biliary  ducts  (fig.  465,') 
commence  within  the  lobules  by  numerous  ramifications,  which 
form  a closed  network  or  plexus,  occupying  principally  the  outer  por- 
tion of  each  lobule.  The  anastomosis  of  the  ducts  was  doubted  by 
Muller,  who,  having  observed  that  in  the  lower  animals,, and  also  in 
the  embryo  of  birds,  the  biliary  ducts  terminate  in  tufts  of  tubes,  having 
free  and  blind  extremities,  thought  it  probable  that  a similar  structure 
existed  in  the  human  liver.  Since  the  discovery  of  the  hepatic  cells, 
both  of  these  views  have  undergone  considerable  modification  in  the 
opinion  of  anatomists.  Thus,  it  is  conceived  by  Krukenberg  and 
Theile  that  the  interstices  between  the  network  of  capillary  blood- 
vessels in  the  lobules  represent  the  reticular  ducts  of  Kiernan;  and, 
further,  that  these  interstices  or  ducts  are  lined,  and  in  a manner  filled 
by  the  secreting  nucleated  hepatic  cells.  It  has  been  questioned 
whether  these  intervascular  spaces  are  bounded  by  a proper  limitary 
or  constituent  membrane,  or  whether  the  nucleated  cells  lie  in  imme- 
diate contact  with  the  coats  of  the  capillaries ; but  the  former  opinion 
is  on  the  whole  the  more  probable.  It  has  been  further  noticed, 
first  by  Dujardin  and  Berger,  and  afterwards  by  Henle,  Muller,  and 
others,  that  the  nucleated  cfells  lie  in  linear  series  between  the  vessels, 
and  for  the  most  part  present  a similar  radiated  arrangement  from  the 
centre  towards  the  margin  of  the  lobules.  E.  H.  Weber  conceived 
that  a single  file  or  row  of  these  cells  was  contained  in  each  of  the 
finest  ducts,  or  rather  formed  the  tubular  cavity  of  such  a duct  by 
successively  opening  into  each  other.  Henld  conceives  that  the  com- 
mencing ducts  are  mere  interstitial  channels  in  a mass  of  cells  filled 
with  bile,  and  that  these  nascent  and  imperfect  ducts  pass  into  others, 
which  have  a distinct  bounding  membrane  and  lining  epithelium.  He 
supposes  that  the  bile  either  exudes  from  the  cells  into  the  intercellular 
channels,  or  escapes  into  these  channels  by  the  destruction  or  solution 
of  the  adjoining  cells,  which  give  place  to  others  successively  under- 
going the  same  process.  Other  anatomists,  again,  as  Theile,  suppose 
that  ducts  do  not  exist  at  all  as  such  wdthin  the  lobules,  but  commence 
upon  their  outer  surface;  and  that  the  secreted  bile  either  finds  its  way 
into  them  by  oozing  through  and  between  the  nucleated  cells,  or  is 
introduced  into  them  by  rupture  and  subsequent  intercommunication 


HEPATIC  CELLS. 


485 


Fig.  466. 


Hepatic  cells.  (Dr.  Baly.) — A. 
From  healthy  human  liver.  B. 
From  a case  oPsupposed  cirrhosis, 
c.  From  the  sheep’s  liver.- 


of  the  cells,  which  is  said  to  take  place  in  succession  along  the  rows 
of  cells  which  radiate  from  the  centre  to  the  margin  of  a lobule. 

The  hepatic  cells. — These  are  nucleated  cells  of  a spheroidal,  com- 
pressed, or  polyhedral  form,  (fig.  466,  a,) 
having  a mean  diameter  of  from  ^^Voth  to 
■j^oth  of  an  inch ; according  to  Henle  they 
are  some  of  them  only  TTre^h  of  an  inch  in 
diameter.  They  present  some  colour  even 
when  highly  magnified,  being  of  a faint 
yellowish  hue.  They  usually  include  a 
very  clear  bright  nucleus  of  a rounded  form, 
within  which  again  one  or  two  nucleoli  may 
be  seen.  The  cells  also  contain  very  fine 
granular  or  vesicular  molecules.  In  many 
cases,  too,  the  cells  of  the  human  liver  and 
of  that  of  quadrupeds  have  larger  and  smaller  semi-transparent  fat- 
globules  in  their  interior.  Their  nucleus  is  frequently  quite  indis- 
tinguishable; and  sometimes,  on  the  other  hand,  cells  are  observed 
which  are  provided  with  two  separate  nuclei.  As  already  stated,  they 
lie  in  rows  or  streaks  amongst  the  vessels,  radiating  from  the  centre  of 
the  lobules  towards  their  circumference. 

Aberrant  biliary  ducts. — In  the  duplicature  of  the  peritoneum  form- 
ing the  left  lateral  ligament  of  the  liver,  and  also  in  the  two  fibrous 
bands  which  sometimes  convert  the  fossa  for  the  vena  cava  and  the 
fissure  of  the  umbilical  vein  into  canals,  there  have  been  found  biliary 
ducts  of  tolerable  size  which  are  not  surrounded  with  lobules.  These 
aberrant  ducts,  as  they  might  be  called,  are  described  by  Ferrein  and 
by  Kiernan : they  anastomose  together  in  form  of  a netw’ork,  and  are 
accompanied  by  branches  of  the  vena  portas,  hepatic  artery,  and  hepa- 
tic vein. 


[“  In  vertebrated  animals  the  liver  is  of  large  size,  and  of  no  general  regular 
form.  It  is  usually  divided  by  deep  fissures  into  several  portions  or  lobes,  which 
are  invested  by  the  peritoneum.  In  colour  it  passes  through  all  the  shades  of 
light  pink  or  nearly  white,  yellow,  red,  brownish  purple,  and  brown.  When  the  sur- 
face is  closely  examined  beneath  the  transparent  peritoneum,  it  will  be  found  to  have 
somewhat  the  appearance  of  a mosaic  structure,  a dark  ground  inlaid  with  small 
portions  of  a lighter  colour.  In  intimate  structure  it  consists  of  numerous,  small, 
irregular  bodies,  or  lobules  (lobules  of  Kiernan),  corresponding  to  the  lighter  por- 
tions just  mentioned,  which  are  lobulated  themselves  and  closely  connected  to- 
gether by  means  of  white  and  yellow  fibrous  tissue  and  the  blood-vessels  belong- 
ing to  the  organ,  which  correspond  to  the  dark  ground-lines  separating  the 
lighter-coloured  masses.  The  lobules  are  not  regularly  arranged  side  by  side 
throughout  the  liver,  but  lie  in  all  directions,  principally,  however,  with  their  long 
diameters  at  right  angles  to  the  surfaces.  When  the  vessels  of  a liver  have  been 
injected,  and  the  organ  then  hardened  in  alcohol  so  that  it  may  be  rendered  more 
consistent  and  its  difference  of  stracture  more  perceptible,  and  a section  made  at 
right  angles  to  the  surfaces  of  the  organ,  a view  like  fig.  467,  will  be  obtained. 
In  such  a section,  lobules  wifi,  be  observed  to  be  cut  in  aU  directions : longitudi- 
nally, when  they  have  a foliated  appearance ; obliquely  or  transversely,  when 
they  have  a more  or  less  polygonal  form,  depending  upon  the  amount  of  mutual 
pressure  at  any  part -of  the  liver,  being  greatest  in  the  interior,  least  near  the  sur- 
face. In  their  interior,  sections  of  blood-vessels  are  seen,  which  belong  to  the 
' hepatic  veins;  and  the  vessels  occupying  the  interspaces  between  them  are 
branches  of  the  hepatic  artery  and  the  vena  portarum.  The  lobules  are  composed 

41* 


486 


BILIARY  TUBES. 


Fig.  467.  Fig.  468. 


Fig.  467.  Longitudinal  section  of  human  liver  from  the  posterior  part  near  the  upper  surface, 
magnified  3 diameters,  f rom  a preparation  made  by  Dr.  Horner.  The  three  sets  of  blood-vessels 
were  injected  with  colouring  malterand  the  preparation  then  preserved  in  alcohol.  The  blood- 
vessels represented  in  the  drawing  belong  to  the  hepatic  veins,  and  are  seen  at  various  parts 
coming  from  the  interior  of  the  lobules.  The  spaces  between  the  lobules,  which  are  filled  with 
branches  of  the  hepatic  artery  and  vena  portarum  and  hepatic  ducts,  have  been  purposely  left 
white,  so  as  not  to  obscure  the  view  of  the  lobules. 

Fig.  468.  Transverse  section  of  a lobule  of  the  human  liver,  taken  from  the  same  preparalio.n 
as  fig.  467,  highly  magnified,  and  presenting  to  view  the  reticulated  structure  of  the  biliary  tubes. 
In  the  centre  of  the  figure  is  seen  the  hepatic  vein  cut  across  and  several  small  branches  termi- 
nating in  it.  Where  the  injecting  matter  did  not  run  freely,  it  is  seen  standing  in  dots  along  the 
course  of  the  vessels.  At  the  periphery  are  seen  branches  of  the  hepatic  artery,  vena  portarum 
and  hepatie  duct. — J.  L ] 

of  an  intertexture  of  biliary  tubes,  (pori  biliari,)  (fig.  468,)  and  in  the  areolee  or 
interspaces  of  the  network  the  blood-vessels  ramify  and  form  amongst  themselves 
an  intricate  anastomosis,  the  whole  being  intimately  connected  together  by  a 
combination  of  the  white  fibrous  and  yellow  elastic  tissue. 

'•  In  structure  the  biliary  tubes  (figs.  469,  470)  correspond  with  those  of  the  in- 


[Fig.  469.  Fig.  470. 


Fig.  469.  A small  portion  of  fig.  468  more  highly  magnified.  The  secreting  cells  are  seen 
within  the  tubes,  and  in  the  interspaces  of  the  latter  the  fibrous  tissue  is  represpnted. 

F ig,  470.  Portion  of  a biliary  tube,  from  a fresh  human  liver,  very  highly  magnified.  The 
secreting  cells  may  be  noticed  to  be  polygonal  from  mutual  pressure. — J.  L.] 


BILIARY  TUBES. 


487 


rertebrata.  consisting  of  cylinders  of  basement  membrane  containing  numerous 
secreting  cells,  and  the  only  difference  exists  in  the  arrangement;  the  free  tubes 
of  the  invertebrata,  in  the  vertebrata  becoming  anastomosed  or  forming  an  in- 
tertexture-  The  tubuli  vary"  in  size  in  an  unimportant  degree  in  different  animals, 
and  also  in  the  same  animal,  being  generally  from  two  to  two  and  a half  times 
the  diameter  of  the  secreting  cells.  The  tubes  of  one  lobule  are  distinct  from 
those  of  the  neighbouring  lobuli,  or  only  communicate  indirectly  by  means  of  the 
trunks  or  hepatic  ducts  originating  from  the  tubes  and  lying  in  the  interspaces  of 
the  lobuli.  The  secreting  cells  are  irregularly  angular,  or  polygonal  in  form  from 
mutual  pressure,  and  line  the  interior  surface  of  the  tubes.  They  vary  in  size  in 
a moderate  degree  in  different  animals  and  also  in  the  same  animal,  appearing 
to  depend  upon  certain  conditions  of  the  animal  and  liver.  The  colour  is  light 
yellowish,  or  brownish  when  in  mass,  the  other  and  darker  colours  of  the  liver 
appearing  to  depend  upon  the  blood  in  the  organ.  They  contain  a fhrely  granular 
matter,  oil-globules,  a granular  nucleus,  and  a transparent  nucleolus. 

“The  finely  granular  matter  is  the  portion  from  which  the  colour  of  the  cell  is 
derived ; it  appears  to  be  made  up  of  mnumerable  exceedingly  minute  spheriform 
granules,  which,  when  under  a low  power  of  the  microscope  and  well  defined, 
look  like  so  many  minute  black  points.  This  substance,  from  its  quantity  and 
minute  state  of  division,  often  obscures  the  nucleus  so  that  it  cannot  be  dis- 
tinguished until  acetic  acid  is  applied  to  it,  when  it  is  rendered  more  translucent 
without  atfecting  the  nucleus.  The  oil  or  fat  varies  in  quantity  in  different  con- 
ditions of  the  liver,  and  in  different  cells.  It  exists  in  the  form  of  exceedingly 
minute  globules,  looking  like  so  many  intensely  black  points,  and  hardly  percep- 
tible from  the  granular  contents  of  the  cells,  up  to  larger  and  distinct  globules, 
sometimes  one-fourth  the  diameter  of  the  cell.  From  the  gradual  advance 
from  a state  hardly  distinguishable  from  the  granular  matter  of  the  cells  up  to  a 
large  size,  and  in  the  invertebrata  even  to  a distended  state  of  the  cell,  a gen- 
tleman, to  whom  I presented  the  observation,  supposed  that  the  liver  only  secreted 
fatty  matter,  while  the  gall-bladder  secreted  cholesterine,  the  latter  fact  being 
presented  to  his  observation  in  several  pathological  cases,  in  which  the  cystic 
duct  was  obstructed  and  the  bladder  filled  with  white  concretions  (biliary  calculi), 
which  consisted  of  pure  cholesterine.  This,  which  appears  plausible  at  first  view, 
falls  at  once  to  the  ground  when  it  is  recollected  that  some  animals  have  no  gall- 
bladder, as  the  horse,  sloth,  &c.,  and  yet  secrete  a bile  constituted  like  that  of 
animals  possessing  a gall-bladder.  The  giraffe,  it  is  also  well  knorvn,  in 
the  three  or  four  cases  in  which  the  animal  has  been  dissected,  in  two  cases 
had  no  gall-bladder,  and  m a third  instance  possessed  one  of  large  size.  I have 
mentioned  that  the  quantity  of  oil-globules  varies  in  different  conditions  of  the 
animal  or  organ.  If  the  animal  be  very  fat,  or  be  well  fed,  especially  on  sub- 
stances containing  much  starch,  it  will  be  found  in  greater  abundance  than  usual; 
as  may  be  readily  seen  m the  difference  between  poultry  which  run  about  and 
those  which  are  penned  up  for  fattening;  and  I have  no  doubt  that  in  the  prepa- 
ration of  the  liver  of  geese,  in  which  it  becomes  enormously  enlarged,  for  making 
the  ^paU  de  foie  gras  de  Strasbourg,’  there  is  not  the  addition  of  a single  secreting 
cell,  but  merely  an  accumulation  of  fat  globules,  within  the  secreting  cellules, 
derived  indirectly  from  the  starchy  matters  of  the  food,  which  ordinarily  are  con- 
sumed in  the  process  of  respiration.  In  phthisis,  in  which  more  or  less  of  the 
respiratory  surface  is  destroyed,  the  liver  appears  to  take  upon  itself  part  of  the 
office  of  the  lungs,  but  rids  the  blood  of  the  excess  of  carbon  in  another  way, 
that  is,  by  converting  it,  with  the  elements  of  water,  into  fat,  which  is  deposited 
within  the  cells,  producing  what  is  called  “ fat  liver.”  The  same  condition  of 
the  liver  is  produced  in  drunkards,  probably  from  the  stimulation  to  nutrition  and 
the  conversion  of  the  alcoholic  constituents  into  fat. 

“ The  nucleus  is  generally  central,  frequently  lateral,  globular,  and  pretty  uni- 
form in  size  in  the  same  animal.  It  is  granular  in  structure  and  never  contains 
oil-globules;  generally,  it  is  but  indistinctly  seen,  excepting  in  fishes  and  reptiles, 
and  frequently  not  at  all,  from  the  granular  contents  of  the  cell  obscuring  it,  but 
is  readily  brought  into  view  by  the  influence  of  acetic  acid  upon  the  latter.  Some- 
times there  are  two  nuclei  instead  of  one. 


488 


EXCRETORY  APPARATUS  OF'  THE  LIVER. 


“The  nucleolus  measures  about  ’001  millimetre,  is  round  in  form,  consistent, 
and  transparent,  and  is  situated  in  the  centre  of  the  nucleus. 

“ The  interlobular  trunks  or  commencement  of  the  hepatic  ducts,  as  they  origi- 
nate from  the  biliary  tubes  or  pores,  run  in  varied  direction  in  regard  to  the  lo- 
bules, and  freely  anastomose  with  each  other,  and  by  their  convergence  form 
trunks  which  take  a general  course  at  right  angles  to  the  surfaces  of  the  liv'er, 
and  finally  appear  by  several  trunks  externally  beneath  the  liver. 

“ The  blood-vessels  of  the  liver  consist  of  two  sets,  the  hepatic  artery  and  vena 
portarum,  which  convey  the  blood  to  it,  and  a third  set,  the  hepatic  veins,  which 
conduct  the  effete  blood  from  it  into  the  general  circulation  again. 

“The  hepatic  artery,  much  smaller  than  the  vena  portarum,  appears  to  be  ap- 
propriated to  the  nutrition  and  supply  of  oxygen  to  the  tissues  entering  into  the 
composition  of  the  liver;  while  the  vena  portarum  is  probably  devoted  to  the 
conveyance  of  blood  to  the  secreting  cells,  which  appropriate  the  peculiar  fluid 
of  the  liver,  or  bile  from  it.  These  two  vessels  enter  the  liver  at  the  place  of  exit 
of  the  hepatic  ducts,  and  follow  the  same  course  inwards  that  the  latter  did  in 
coming  out.  The  artery  in  its  passage  supplies  the  duct  with  branches  and  the 
vena  portarum  with  vasa  vasorum.  In  the  intervals  of  the  lobules  they  comport 
themselves  very  much  in  the  manner  of  the  interlobular  ducts,  and  form  an  intri- 
cate network  around  the  lobules,  but  whether  the  two  sets  of  vessels  anastomose 
I could  not  satisfactorily  determine.  They  both  send  off  numerous  branches, 
which  enter  the  lobules  at  right  angles  to  the  length  of  the  latter,  and  form  an 
intricate  plexus  by  turning  through  the  interspaces  of  the  biliary  tubes.  The 
vessels  within  the  lobules  freely  communicate  with  each  other  and  converge 
towards  their  interior,  where  they  terminate  in  trunks,  ■which  run  in  the  length 
of  the  lobules,  and  are  the  commencement  of  the  hepatic  veins.  This  free  in- 
tercommunication of  the  three  sets  of  vessels  within  the  lobules  has  been  fairly 
proved  to  me  by  a minute  injection  of  a young  liver,  made  by  Dr.  Horner,  and 
preserved  in  the  Wistar  Museum. 

“ The  commencing  branches  of  the  hepatic  veins  issue  from  the  base  of  the 
lobules,  and  by  their  convergence,  form  several  large  trunks,  which  pass  out  of 
the  liver  at  right  angles  to  the  other  two  sets  and  parallel  to  its  surfaces,  at  its 
dorsal  margin  close  to  the  spinal  column.” — J.  L.]* 

THE  BILE. 

The  bile,  as  it  flows  from  the  liver,  is  a thin  greenish  yellow  fluid;  but  that 
which  remains  in  the  gall-bladder  becomes  darker,  more  viscid,  and  ropy,  It 
contains  as  adventitious  particles  mucus  and  epithelium  corpuscles.  The  spe- 
cific gravity  of  the  bile  is  from  1-026  to  1-030.  It  has  a sweetish  bitter  taste,  and 
an  alkaline  reaction.  It  is  a saponaceous  compound,  containing  the  following 
ingredients  : — water,  mucus,  colouring  matters  (composed,  according  to  Berzelius, 
of  a yellow  substance  named  cholepyrrhine,  a brown  substance  named  bilifulvine, 
and  a green  matter  or  biliverdine),  ratty  acids,  viz.,  the  margaric  and  oleic,  com- 
bined with  soda,  free  fat,  cholesterine,  salts,  and,  lastly,  the  most  important  ingre- 
dient of  the  bile,  namely,  choleic  or  bilic  acid,  a resinous  or  fatty  acid,  which  is 
also  in  a state  of  combination  with  soda.  This  choleic  acid  consists  principally 
of  carbon  and  hydrogen,  but  it  also  contains  nitrogen  and  sulphur;  it  is  very 
easily  decomposed,  and  gives  rise  , to  ammoniacal  and  other  compounds. 

THE  EXCRETORY  APPARATUS  OF  THE  LIVER. 

The  excretory  apparatus  of  the  liver  consists  of  the  hepatic  duct, 
the  cystic  duct,  the  gall-bladder,  and  the  common  bile-duct,  or  ductus 
communis  choledochus. 

The  hepatic  duct,  (fig.  473,)  commencing  at  the  transverse  fissure 
of  the  liver,  descends  to  the  right,  -within  the  gastro-hepatic  omentum, 
in  front  of  the  vena  portae,  and  to  the  right  of  the  hepatic  artery.  Its 

* [Researches  into  the  Comparative  Structure  of  the  Liver,  by  Joseph  Leidy,  M.D., 
Amer.  Jour,  of  .Med.  Science,  Phil.  Jan.  1848. — J.  L.] 


STRUCTURE  OF  GALL-BLADDER. 


489 


diameter  is  about  two  lines,  and  its  length  nearly  two  inches.  At  its 
lower  end  it  meets  with  the  cystic  duct,  coming  down  from  the  gall- 
bladder; and  the  tw'o  ducts  uniting  together  at  an  acute  angle,  form 
the  ductus  communis  choledochus  (f). 

The  gall-bladder  {g)  is  a pear-shaped  membranous  sac,  about  three 
or  four  inches  long,  rather  more  than  an  inch  across  at  its  widest 
part,  and  capable  of  containing  about  eight  or  ten  fluid-drachms. 
It  is  lodged  obliquely  in  a fossa  on  the  under  surface  of  the  right  lobe 
of  the  liver,  so  that  its  large  end  or  fundus,  which  projects  beyond  the 
anterior  border  of  the  gland,  is  directed  downwards,  forwards,  and  to 
the  right,  w'hilst  its  body  and  narrow  end  or  neck  are  inclined  in  an 
opposite  direction,  viz.,’  upw’ards,  backwards,  and  to  the  left. 

The  upper  surface  of  the  gall-bladder  is  attached  to  the  liver  by 
cellular  tissue  and  vessels,  along  the  fossa  formed  between  the  square 
lobe  and  the  remainder  of  the  right  lobe.  Its  under  surface  '\s  free 
and  covered  by  the  peritoneum,  which  is  here  reflected  from  the  liver, 
so  as  to  include  and  support  the  gall-bladder  from  below.  Sometimes, 
however,  the  peritoneum  completely  surrounds  the  gall-bladder,  which 
is  then  suspended  by  a kind  of  mesentery  at  a little  distance  from  the 
under  surface  of  the  liver.  The  fundus  of  the  gall-bladder,  which  is 
free,  projecting,  and  always  covered  with  peritoneum,  touches  the 
abdominal  parietes  immediately  beneath  the  margin  of  the  thorax, 
opposite  the  tip  of  the  tenth  costal  cartilage.  Below,  it  rests  on  the 
commencement  of  the  transverse  colon  ; and,  further  back,  the  gall- 
bladder is  in  contact  with  the  duodenum,  and  sometimes  with  the 
pyloric  extremity  of  the  stomach.  In  consequence  of  these  relations 
with  the  hollow  viscera  and  with  the  surface,  gall-stones  occasionally 
make  their  way  from  the  gall-bladder  into  the  intestines,  or  even  exter- 
nally, by  a process  of  adhesion  and  ulcerative  absorption.  The  neck 
of  the  gall-bladder,  which  is  gradually  narrowed,  forms  two  curves 
upon  itself  like  an  S,  and  then,  having  become  much  constricted,  and 
changing  its  general  direction  altogether,  bends  downwards  and  ter- 
minates in  the  cystic  duct. 

Structure. — Besides  the  peritonea!  investment,  the  gall-bladder  has 
two  distinct  tunics,  viz.,  a cellular  and  a mucous  coat. 

The  cellular  coat  is  strong,  and  consists  of  bands  of  dense  shining 
white  fibres,  which  interlace  in  all  directions.  These  fibres  resemble 
those  of  cellular  tissue;  and,  as  a matter  of  inference  only,  they  are 
supposed  to  possess  contractility.  In  recently  killed  quadrupeds  the 
gall-bladder  contracts  on  the  application  of  a stimulus;  and  in  the 
larger  species,  such  as  the  ox,  muscular  fibres  of  the  plain  variety 
have  been  found  in  this  coat.  It  forms  the  framework  of  the  organ, 
and  supports  the  larger  blood-vessels  and  lymphatics. 

The  mucous  coat,  which  is  generally  strongly  tinged  of  a yellowish 
browm  colour  with  bile,  is  elevated  upon  its  inner  surface  into  innume- 
rable ridges,  which,  uniting  together  into  meshes,  leave  between  them 
depressions  of  different  sizes  and  of  various  polygonal  forms.  This 
structure  gives  to  the  interior  of  the  gall-bladder  an  areolar  aspect, 
which  is  similar  to  what  is  seen  on  a smaller  scale  in  the  vesiculse 
seminales.  These  areolar  intervals  become  smaller  towards  the  fundus 


490 


COMMON  BILE-DUCT. 


and  neck  of  tlie  gall-bladder;  and  at  the  bottom  of  the  larger  ones, 
other  minute  depressions,  rendered  visible  by  a lens,  apparently  lead 
into  numerous  mucous  recesses  or  follicles.  The  whole  of  the  mucous 
membrane  is  covered  by  columnar  epithelium,  and  it  secretes  an 
abundance  of  viscid  mucus. 

At  the  points  where  the  neck  of  the  gall-bladder  curves  on  itself, 
there  are  strong  folds  or  projections  of  its  mucous  and  cellular  coats 
into  the  interior. 

The  gall-bladder  is  supplied  with  blood  by  the  cystic  branch  of  the 
right  division  of  the  hepatic  artery,  along  which  vessel  it  also  receives 
nerves  from  the  coeliac  plexus.  The  cystic  veins  empty  themselves 
into  the  vena  portoB.  The  lymphatics  join  those  of  the  liver. 

The  gall-bladder  is  a receptacle  or  reservoir  for  such  bile  as  is  not 
immediately  required  in  digestion.  The  bile  contained  within  it 
becomes  darker  and  inspissated,  receiving  some  addition  of  mucus, 
and  becoming  more  ropy  and  viscid,  but  beyond  this  it  undergoes  no 
further  change. 

The  cystic  duct  is  about  an  inch  or  rather  more  in  length.  It  runs 
downward  and  to  the  left,  thus  forming  an  angle  with  the  direction  of 
the  gall-bladder,  and  unites  with  the  hepatic  duct  to  form  the  ductus 
communis.  In  its  interior,  the  mucous  membrane  is  elevated  in  a 
singular  manner  into  a series  of  crescentic  folds,  which  are  arranged  in 
an  oblique  direction,  and  succeed  closely  to  each  other,  so  as  to  pre- 
sent very  much  the  appearance  of  a continuous  spiral  valve.  When 
distended,  the  outer  surface  of  the  duct  appears  to  be  indented  in  the 
situation  of  these  folds,  and  dilated  or  swollen  in  the  intervals,  so  as  to 
present  an  irregularly  sacculated  or  twisted  appearance. 

The  common  bile-duct  (fig.  473,  f:  ductus  communis  choledoc/ms), 
the  largest  of  the  three  ducts,  being  from  two  to  three  lines  in  width, 
and  nearly  three  inches  in  length,  conveys  the  bile  both  from  the  liver 
and  the  gall-bladder  into  the  duodenum.  It  continues  downwards  and 
backwards  in  the  course  of  the  hepatic  duct,  between  the  layers  of  the 
gastro-hepatic  omentum,  in  front  of  the  vena  portae,  and  to  the  right 
of  the  hepatic  artery.  Having  reached  the  descending  portion  of  the 
duodenum,  it  continues  downwards  on  the  inner  and  posterior  aspect 
of  that  part  of  the  intestine,  covered  by  or  included  in  the  head  of  the 
pancreas,  and,  for  a short  distance,  in  contact  with  the  right  side  of 
the  pancreatic  duct.  Together  with  that  duct,  it  then  perforates  the 
muscular  wall  of  the  intestine,  and  after  running  obliquely  for  three- 
quarters  of  an  inch  between  its  several  coats,  and  forming  an  eleva- 
tion beneath  the  mucous  membrane,  it  becomes  somewhat  constricted, 
and  opens  by  a common  orifice  with  the  pancreatic  duct  on  the  inner 
surface  of  the  duodenum,  at  the  junction  of  the  second  and  third  por- 
tions of  that  intestine,  and  rather  more  than  three  inches  below  the 
pylorus. 

Structure. — 'The  structure  of  all  the  bile-ducts  is  alike.  Their  cellu- 
lar coat  is  strong  and  distensible.  The  mucous  membrane  is  provided 
with  numerous  glands,  the  openings  of  which  are  scattered  irregularly 
in  the  larger  ducts,  but  in  the  small  subdivisions  of  the  hepatic  duct 
are  arranged  in  two  longitudinal  rows,  one  at  each  side  of  the  vessel. 


DEVELOPMENT  OF  LIVER. 


491 


The  mouths  of  these  glands  have  been  long  known,  and  were  sup- 
posed to  be  merely  tbe  openings  of  mucous  follicles  ; but  the  structure 
of  the  glands  of  the  biliary  ducts  has  been  recently  found  by  Theile  to 
be  more  complicated.  According  to  his  observations,  which  we  have 
been  able  to  confirm,  some  of  them  are  ramified  tubes,  which  occa- 
sionally anastomose  together,  and  often  present  lateral  saccular  dilata- 
tions similar  to  the  Meibomian  glands.  Others,  again,  which  are 
more  solid  and  clustered  together,  are  little  cellular  glands  opening 
into  the  bile-duct  by  a single  orifice.  Sometimes  these  cellular  glands 
are  attached  to  the  tubular  glands,  and  open  into  them. 

Development. — According  to  some  the  gall-bladder  is  developed  as  a branch  or 
diverticulum  from  the  bile-duct  outside  the  liver;  but  Meckel  says  it  arises  in  a 
deep  notch  in  the  substance  of  the  gland.  It  is  at  first  tubular,  and  then  has  a 
rounded  form.  The  alveoli  in  its  interior  appear  about  the  sixth  month.  At  the 
seventh  month  it  first  contains  bile.  In  the  fcetus  its  direction  is  more  horizontal 
than  in  the  adult. 

Varieties  in  the  excretory  apparatus  of  the  liver. — The  gall-bladder  is  occasionally 
wanting;  in  which  case  the  hepatic  duct  is  much  dilated  within  the  liver,  or  in 
some  part  of  its  course.  Sometimes  the  gaU-bladder  is  irregular  in  form,  or  is 
constricted  across  its  middle,  or,  but  much  more  rarely,  it  is  partially  divided  in 
a longitudinal  direction.  Direct  communications  by  means  of  small  ducts, 
(named  hepato-cystic,)  passing  from  the  liver  to  the  gaU-bladder,  exist  regularly 
in  various  animals ; and  they  are  sometimes  found,  as  an  unusual  formation,  in 
the  human  subject. 

The  right  and  left  divisions  of  the  hepatic  duct  sometimes  continue  separate 
for  some  distance  within  the  gastro-hepatic  omentum.  Lastly,  the  common  bile- 
duct  not  unfrequently  opens  into  the  duodenum,  apart  from  the  pancreatic  duct. 

DEVELOPMENT  AND  FCETAL  PECULIARITIES  OF  THE  LIVER. 

The  liver  begins  to  be  formed  at  a very  early  period  of  foetal  life.  Its  develop- 
ment has  been  traced  in  the  bird  (fig.  471)  from  a conical  protrusion  of  the  in- 
testinal canal  (c),  surrounded  by  a soft  mass  or  blastema  (d),  in  which,  by  a sub- 
sequent process  of  growth,  the  ducts  are  formed.  In  the  mammalian  embryo 
(the  dog)  it  has  been  found  by  BischofF  to  commence  by  a double  mass  of  blas- 
tema attached  to  the  outer  wall  of  the  intestinal  tube  immediately  beneath  the 
dilatation  for  the  stomach,  and  having  a conical  protrusion  of  the  internal  mem- 
brane passing  into  each  division  of  the  mass.  In  a very  early  condition,  ramified 
lines  or  commencing  ducts  may  be  seen  as  in  other  glands ; but  this  appearance 
is  not  afterwards  visible,  owing  to  the  thickness  and  colour  of  the  gland,  and  also 
in  consequence  of  the  development  of  nucleated  cells. 

Size. — In  the  human  fcetus,  at  the  third  or  fourth  week,  the  liver  is  said  to  con- 
stitute one  half  the  weight  of  the  whole  body.  This  proportion,  however,  gradu- 
ally decreases  as  development  advances,  until  at  the  full  period  the  relative 
weight  of  the  foetal  liver  to  that  of  the  body  is  as  1 to  18. 

In  the  early  foetus  the  right  and  left  lobes  of  the  liver  are  of  equal,  or  nearly 
equal,  size ; and  just  before  birth  the  difference  between  them  is  not  great,  the 
relative  weight  of  the  left  lobe  to  the  right  being  nearly  as  1 to  1-6. 

Position. — In  consequence  of  the  greater  equality  as  to  size  between  the  two 
lobes,  the  position  of  the  foetal  liver  in  the  abdomen  is  more  symmetrical,  as  regards 
the  middle  line  of  the  body.  In  the  very  early  fcetus  it  occupies  nearly  the  whole 
of  the  abdominal  cavity ; and  at  the  full  period  it  stdl  descends  an  inch  and  a 
half  below  the  margin  of  the  thorax,  overlaps  the  spleen  on  the  left  side,  and 
reaches  nearly  down  to  the  crest  of  the  ilium  on  the  right. 

Form,  Colour,  ^c. — ^The  foetal  liver  is  thicker  from  above  downwards,  and  has 
therefore  a rounder  form  than  in  the  adult.  It  is  generally  of  a darker  hue.  Its 
consistence  and  specific  gravity  are  both  less  than  in  the  adult. 

Blood-vessels. — Lastly,  the  blood-vessels  of  the  foetal  liver  present  most  important 
peculiarities,  with  which,  indeed,  aU  those  previously  mentioned  are  more  or  less 
connected. 


492 


CHANGES  IN  LIVER. 


Fig.  472. 


Fiff.  471.  Early  condition  of  the  liver  in  the  chick  at  the  fifth  day  of  incubation.  (Miiller.)— 
n.  The  heart,  as  a simple  curved  tube.  b.  The  intestinal  tube.  c.  Contcal  protrtision  of  the 
coat  of  the  commencing  intestine,  on  which  the  bl.astema  of  the  liver  is  formed,  d.  The  rudi- 
mentary liver,  e.  Portion  of  the  mucous  layer  of  the  germinal  membrane. 

Fig.  472.  Under  surface  of  the  foeial  liver,  with  its  great  blood-vessels,  at  the  full  period. 
The  rounded  outline  of  the  organ,  atid  the  comparatively  small  difference  of  size  between  its 
two  lobes.  ,nre  seen.  a.  The  umbilical  vein,  lying  in  the  umbilical  fissure,  and  turning  to  the 
right  side  at  the  transverse  fissure  (o),  to  join  the  vena  portie  (p) : the  branch  marked  d,  named 
the  ductus  venosus,  continues  straight  on  to  join  the  vena  cava  inferior  (c).  A few  branches  of 
the  umbilical  vein  enter  the  substance  of  the  Itver  at  once.  g.  The  gall-bladder.  (After  an 
enlarged  model.) 

Up  to  the  moment  of  birth  most  of  the  blood  returned  from  the  placenta  by  the 
umbilical  vein  passes  through  the  liver  of  the  foetus  before  it  reaches  the  heart. 
At  this  period  the  umbilical  vein  runs  from  the  umbilicus  along  the  free  margin 
of  the  su.spensory  ligament  towards  the  anterior  border  and  under  surface  of  the 
liver,  beneath  which  it  is  lodged  (fig.  472,’)  in  the  umbilical  fissure,  and  proceeds 
as  far  as  the  transverse  fissure.  Here  it  divides  into  two  branches ; one  of  these 
('*),  the  smaller  of  the  two,  continues  onwards  in  the  same  direction,  and  joins 
the  vena  cava  ('=)  ; this  is  the  ductus  venosus,  which  occupies  the  posterior  part  of 
the  longitudinal  fissure,  and  gives  to  it  the  name  of  the  fossa  of  the  ductus  veno- 
sus. The  other  and  larger  branch  (the  trunk  of  the  umbilical  vein)  turns  to  the 
right  along  the  transverse  or  portal  fissure  (“),  and  ends  in  the  vena  portas  (p), 
which  in  the  fcetus  is  of  comparatively  small  dimensions.  Moreover,  the  umbi- 
lical vein,  as  it  lies  in  the  umbilical  fissure,  and  before  it  joins  the  vena  portae, 
gives  off  some  lateral  branches,  which  enter  the  left  lobe  of  the  liver.  It  also 
sends  a few  branches  to  the  square  lobe  and  to  the  lobe  of  Spigelius. 

The  blood  of  the  umbilical  vein  therefore  reaches  the  ascending  vena  cava  in 
three  different  ways.  Some  passes  directly  into  it  by  the  ductus  venosus ; another, 
and  the  principal  portion,  passes  first  through  the  portal  veins,  and  then  through 
the  hepatic  veins ; whilst  a third  portion  enters  the  liver  directly,  and  is  also  re- 
turned to  the  cava  by  the  hepatic  veins. 

Changes  after  birth. — Immediately  after  birth,  at  the  cessation  of  the  current 
hitherto  passing  through  the  umbilical  vein,  and  at  the  commencement  of  an 
increased  circulation  through  the  lungs,  the  supply  of  blood  to  the  liver  is  dimi- 
nished perhaps  two-thirds.  The  umbilical  vein  and  ductus  venosus  become 
empty  and  contracted,  and,  soon  after,  they  begin  to  be  obliterated,  and  are  ulti- 
mately converted  into  the  fibrous  cords  already  described — that  one  which  repre- 
sents the  umbilical  vein,  constituting  the  round  ligament  of  the  liver.  At  the  end 
of  six  days  the  ductus  venosus  has  been  found  to  be  closed;  but  it  sometimes 
continues  open  for  several  weeks. 

Concurrently  with,  and  doubtless  in  some  measure  dependent  on,  the  sudden 
diminution  in  the  quantity  of  blood  supplied  to  the  liver  after  birth,  this  organ 
appears  at  first  to  become  absolutely  lighter ; and,  according  to  some  data,  this 
decrease  of  weight  is  not  recovered  from  until  the  conclusion  of  the  first  year. 
After  that  period,  the  liver,  though  it  increases  in  size,  grows  more  slowly  than 


PANCREAS. 


493 


the  body,  so  that  its  relative  weight  in  regard  to  the  body,  which  was  1 to  18  just 
before  birth,  becomes  gradually  less  and  less.  At  about  five  or  si.v  years  of  age 
it  has  reached  the  proportion  maintained  during  the  rest  of  life,  viz.,  1 to  36. 

The  relative  weight  of  the  left  lobe  to  that  of  the  right  (which,  as  above  stated, 
is  about  1 to  1'6  immediately  before  birth)  undergoes  a diminution  afterwards. 
Thus,  at  a month  old,  it  has  been  found  to  be  as  1 to  3,  and  in  after  life  the  pro- 
portion is  generally  1 to  4 or  5. 

Varieties. — The  liver  is  not  subject  to  great  or  frequent  deviation  from  its  ordi- 
nary characters.  Sometimes  it  retains  the  thick  rounded  form  which  it  presents 
in  the  fostus;  and  it  has  occasionally  been  found  without  any  division  into  lobes. 
On  the  contrary,  Scnmmerring  has  recorded  a case  in  which  the  adult  liver  was 
divided  into  twelve  lobes  : and  similar  cases  of  multiple  liver  (resembling  that 
of  some  animals)  have  been  now  and  then  observed  by  others.  A detached 
portion,  forming  a sort  of  accessory  liver,  is  occasionally  found  appended  to  the 
left  extremity  of  the  gland  by  a fold  of  peritoneum  containing  blood-vessels. 

THE  PANCREAS. 

The  pancreas  (fig.  473,  h,  t:  ■na.g  x^sas,  all  flesh)  is  a long,  narrow, 
flattened  gland,  larger  at  one  end  than  the  other,  which  lies  deeply  in 
the  cavity  of  the  abdomen,  immediately  behind  the  stomach,  and  op- 


Fig.  473. 


In  this  figure,  which  is  altered  from  Tiedemann,  the  liver  and  stomach  are  turned  up,  to  show 
the  duodenum,  the  pancreas,  and  the  spleen.  1.  The  undersurface  of  the  liver,  g.  Gall-bladder. 
/.  The  common  bile-duct,  formed  by  the  union  of  a duct  from  the  gall-bladder,  called  the  cystic 
duct,  and  of  the  hepatic  duct  coming  f om  the  liver.  ‘ o.  The  cardiac  end  of  the  stomach,  where 
the  oesophagus  enters,  s.  Under  surface  of  the  stomach,  p.  Pyloric  end  of  stomach,  d.  Duode- 
num, h.  Head  of  pancreas  ; t,  tail ; and  i,  body  of  that  gland.  The  substance  of  the  pancreas  is 
removed  ^n  front,  to  show  the  pancreatic  duct  (e)  and  its  branches,  r.  The  spleen,  v.  The  hilus, 
at  which  the  blood-vessels  enter,  c.  Crura  of  diaphragm,  n.  Superior  mesenteric  artery,  a. 
Aorta. 

posite  the  first  lumbar  vertebra.  Its  larger  end,  which  is  turned  to  the 
right,  is  embraced  by  the  curvature  of  the  duodenum,  whilst  its  left  or 
narrow  extremity  reaches  to  a somewhat  higher  level,  and  is  in  con- 
tact with  the  spleen.  It -extends,  therefore,  across  the  epigastric  into 
both  hypochondriac  regions. 

In  its  general  form  the  pancreas  bears  some  resemblance  to  a 
hammer,  or,  what  is  a better  comparison,  to  a dog’s  tongue.  Its  broad 
end  is  named  the  head  {h),  the  narrow  extremity  the  tail  (t),  and  the 
intermediate  portion,  which  is  compressed  in  front  and  behind,  the 
body  of  the  gland  (i). 

VOL.  II. 


42 


494 


STRUCTURE  OF  PANCREAS. 


The  right  or  large  end  of  the  pancreas  is  bent  from  above  down- 
wards, and  accurately  fills  the  curvature  of  the  duodenum.  The  lower 
extremity  of  this  curved  portion  passes  to  the  left,  behind  the  superior 
mesenteric  vessels,  forming  the  posterior  wall  of  the  canal  in  which 
they  are  enclosed.  This  part  of  the  gland  is  sometimes  marked  off 
from  the  rest,  and  is  then  named  the  lesser  paiicreas. 

The  pancreas  varies  considerably,  in  diflerent  cases,  in  its  size  and 
weight.  It  is  usually  from  6 to  8 inches  long,  about  H inch  in  average 
breadth,  and  from  half  an  inch  to  an  inch  in  thickness,  being  thicker 
at  its  head  and  along  its  uppei;  border  than  elsewhere.  The  weight  of 
the  gland,  according  to  Krause  and  Clendinning,  is  usually  from  2i 
oz.  to  85  oz. ; but  Meckel  has  noted  it  as  high  as  6 oz.,  and  Soemmer- 
ring  as  low  as  H oz. 

The  principal  attachment  of  the  pancreas  is  to  the  duodenum  (d), 
with  which  it  is  connected  by  numerous  blood-vessels  and  cellular 
tissue,  but  more  particularly  by  its  own  excretory  duct  or  ducts.  It 
is  also  retained  in  its  position  by  its  connexion  with  several  large 
blood-vessels,  and  by  a layer  of  the  peritoneum.  Thus,  its  anterior 
surface,  concealed  by  the  lower  border  of  the  stomach,  which  moves 
freely  over  the  gland,  is  covered  by  that  part  of  the  peritoneum  which 
forms  the  ascending  layer  of  the  transverse  mesocolon,  along  the  root 
of  which  the  gland  may  be  said  to  lie.  Behind,  the  pancreas  is  attached 
by  cellular  tissue  to  the  vena  cava,  the  aorta,  the  superior  mesenteric 
artery  (n)  and  vein,  the  commencement  of  the  vena  portae,  and  the 
pillars  of  the  diaphragm,  all  of  which  parts,  besides  many  lymphatic 
vessels  and  glands,  are  interposed  between  it  and  the  upper  lumbar 
vertebra.  To  the  left  of  the  vertebral  column,  the  pancreas  is  attached 
behind  in  a similar  way  to  the  left  supra-renal  capsule  and  kidney  and 
to  the  renal  vessels.  Of  the  large  vessels  situated  behind  the  pancreas, 
the  superior  mesenteric  artery  and  vein  are  embraced  by  the  substance 
of  the  gland,  so  as  sometimes  to  be  enclosed  in  a complete  canal, 
through  which  they  pass  downwards  and  forwards,  and  then  appear 
beneath  the  lower  border  of  the  pancreas,  between  it  and  the  termina- 
tion of  the  duodenum.  The  coeliac  axis  is  above  the  pancreas;  and 
lying  in  a groove  along  the  upper  border  of  the  gland  are  found  the 
splenic  artery  and  vein,  the  vein  pursuing  a straight,  and  the  artery  a 
tortuous  course  (figs.  247,  263).  Both  of  these  vessels  supply  nume- 
rous branches  to  the  body  and  tail  of  the  pancreas,  the  narrow  extre- 
mity of  which  is  thus  suspended  or  attached  to  the  inner  border  of  the 
spleen.  The  head  of  the  pancreas,  embraced  by  tbe  inner  curved 
border  of  the  duodenum,  is  attached  more  particularly  to  the  descending 
and  transverse  portions  of  that  intestine,  beyond  which  it  projects 
somewhat  both  in  front  and  behind.  The  ductus  communis  choledo- 
chus  passes  down  behind  the  head  of  the  pancreas,  and  is  generally 
received  into  a sort  of  groove  or  canal  in  its  substance. 

Structure. — The  pancreas  belongs  to  the  class  of  compound  con- 
glomerate glands.  In  its  general  characters,  and  also  in  its  intimate 
structure,  it  closely  resembles  the  salivary  glands,  but  it  is  somewhat 
looser  and  softer  in  its  texture.  It  consists  of  numerous  lobes  and 
lobules,  of  various  sizes,  held  together  by  cellular  tissue,  blood-vessels, 


PANCREATIC  DUCT. 


495 


and  ducts.  The  cellular  tissue  penetrates  between  the  larger  and 
smaller  lobules,  and  connects  them  more  or  less  firmly  together  into 
groups  and  into  a whole;  it  also  serves  to  attach  the  entire  gland  to 
adjacent  parts,  but  it  forms  no  consistent  investment  or  capsule  around 
it.  The  lobules,  aggregated  into  masses,  are  rounded  or  slightly  flat- 
tened at  the  sides,  so  as  to  be  moulded  or  adjusted  compactly  to  each 
other;  their  substance  is  of  a reddish  cream-colour,  and  the  arrange- 
ment of  the  commencing  ducts  and  vessels  is  similar  to  that  in  the 
lobules  of  the  parotid  gland,  which  has  been  already  described  (p. 
438). 

The  principal  excretory  duct,  called  the  -pancreatic  duct  (fig.  473, 
e),  or  the  canal  of  Wirsung,  (by  whom  it  was  discovered  in  the  human 
subject  in  1642,)  runs  through  the  entire  length  of  the  gland,  from  left 
to  right,  buried  completely  in  its  substance,  and  placed  rather  nearer 
its  lower  than  its  upper  border.  Commencing  by  the  union  of  the 
small  ducts  derived  from  the  groups  of  lobules  composing  the  tail  of 
the  pancreas,  and  receiving  in  succession  at  various  angles,  and  from 
all  sides,  the  ducts  from  the  body  of  the  gland,  the  canal  of  Wirsung 
increases  in  size  as  it  advances  towards  the  head  of  the  pancreas, 
where,  amongst  other  large  branches,  it  is  usually  joined  by  one 
derived  from  that  portion  of  the  gland  called  the  lesser  pancreas. 
Curving  slightly  dowmwards,  the  pancreatic  duct  then  comes  into 
contact  with  the  left  side  of  the  ductus  communis  choledochus,  which 
it  accompanies  to  the  back  part  of  the  descending  portion  of  the  duo- 
denum. Here  the  two  ducts,  placed  side  by  Side,  pass  very  obliquely 
through  the  muscular  and  cellular  coats  of  the  intestine,  and  terminate, 
as  already  described,  (p.  490,)  on  its  internal  mucous  surface,  by  a 
common  orifice,  situated  at  the  junction  of  the  descending  and  hori- 
zontal portions  of  the  duodenum,  between  three  and  four  inches  below 
the  pylorus.  It  sometimes  occurs  that  the  pancreatic  duct  and  the 
common  bile-duct  open  separatdy  into  the  duodenum.  The  pan- 
creatic duct,  with  its  branches,  is  readily  distinguished  from  the 
glandular  substance,  from  the  very  white  appearance  of  its  thin  fibrous 
W'alls.  Its  widest  part,  near  the  duodenum,  is  from  1 line  to  \h  line 
in  diameter,  or  nearly  the  size  of  an  ordinary  quill ; but  it  may  be 
easily  distended  beyond  that  size.  It  is  lined  by  a remarkably  thin 
and  smooth  mucous  membrane,  w'hich  near  the  termination  of  the 
duct  occasionally  presents  a few  scattered  follicles. 

Sometimes  the  pancreatic  duct  is  double  up  to  its  point  of  entrance 
into  the  duodenum  ; and  a still  further  deviation  from  the  ordinary 
condition  is  not  unfrequently  observed,  in  which  there  is  a supplementary 
duct,  derived  from  the  lesser  pancreas  or  some  part  of  the  head  of  the 
gland,  opening  into  the  duodenum  by  a distinct  orifice,  at  a distance 
of  even  one  inch  or  more  from  the  termination  of  the  principal  duct. 
Like  the  salivary  glands,  the  pancreas  receives  its  blood-vessels  at  all 
points.  Iis  arteries  are  derived  chiefly  from  the  pancreatico-duodenal 
branch  of  the  hepatic  artery,  and  from  the  splenic  artery ; but  it  also 
receives  branches  from  the  root  of  the  superior  mesenterip.  Its  blood 
is  returned  by  the  splenic  and  superior  mesenteric  veins.  Its  lympha- 


496 


SPLEEN. 


tics  terminate  in  the  lumbar  vessels  and  glands.  The  nerves  of  the 
pancreas  are  derived  from  the  solar  plexus. 

Development. — In  its  origin  and  development,  the  pancreas  altogether  resembles 
the  salivarj-  glands.  It  appears  a little  earlier  than  these  glands,  in  the  form  of 
a small  bud  from  the  left  side  of  the  intestinal  tube,  close  to  the  commencing 
spleen. 

Secretion. — The  fluid  secreted  by  the  pancreas,  called  the  pancreatic  juice,  flows 
into  the  duodenum  through  the  common  orifice  of  the  two  ducts,  probably  accom- 
panied by  some  bile,  and,  then  being  mixed  with  the  chyme,  assists  in  the  further 
changes  of  the  latter.  Owing  to  the  striking  resemblances  in  structure  between 
tire  pancreas  and  the  salivary  glands,  the  former  was  named  by  the  German 
anatomists  the  abdominal  salivary  gland ; but  recent  analyses  have  shown  some 
important  differences  in  the  constitution  of  their  respective  secretions.  Like  the 
saliva,  the  pancreatic  juice  is  a clear  colourless  fluid,  which  has  diffused  in  it  a 
few  microscopic  corpuscles;  it  presents  sometimes  an  acid  and  sometimes  an 
alkaline  reaction,  and  it  contains  mucus,  chloride  of  sodium,  phosphate  and 
sulphate  of  soda,  and  phosphate  and  carbonate  of  lime.  It  differs  from  saliva,  in 
having  a larger  proportion  of  solid  constituents,  in  containing  albumen  and  caseine, 
and  in  bemg  quite  free  from  sulphocyanogen. 

THE  SPLEEN. 

The  spleen  (fig.  473,  r:  lien,  is  a soft,  highly  vascular,  and 

easily  distensible  organ,  of  a dark  bluish  or  purplish  gray  colour.  It 
is  situated  in  the  left  hypochondrium,  at  the  cardiac  end  of  the 
stomach,  between  that  viscus  and  the  diaphragm,  and  is  protected  by 
the  cartilages  of  the  ribs.  Though  extraordinarily  rich  in  blood-ves- 
sels, the  spleen  has  no  excretory  duct;  it  is  therefore  associated  by 
anatomists  with  the  thyroid  body  and  supra-renal  capsules,  as  one  of 
the  class  of  blood-glands  or  vascular  glands. 

The  shape  of  the  spleen  is  irregular  and  somewhat  variable:  it 
forms  a compressed  oval  mass,  placed  nearly  vertically  in  the  body, 
and  having  two  faces,  one  external,  convex  and  free,  which  is  turned 
to  the  left,  the  other  internal  and  concave,  which  is  directed  to  the 
right,  and  is  applied  to, the  cardiac  end  or  great  cul-de-sac  of  the 
stomach.  The  borders  or  circumference  resulting  from  the  junction 
of  these  two  faces  may,  for  the  purposes  of  description,  be  conveniently 
considered  as  forming  an  anterior  and  a posterior  border,  and  an 
upper  and  lower  end. 

The  external  free  convex  face  of  the  spleen,  smooth  and  covered  by 
the  peritoneum,  is  in  contact  with  the  under  surface  of  the  left  side  of 
the  diaphragm,  and  corresponds  with  the  ninth,  tenth,  and  eleventh 
ribs.  The  internal  concave  face  is  irregular,  and  is  divided  into  two 
unequal  portions  or  surfaces,  one  anterior  and  larger,  the  other  poste- 
rior and  smaller,  which  meet  at  a longitudinal  or  vertical  fissure, 
named  the  hlhis  or  fissure  of  the  spleen  (t>).  Along  the  bottom  of  this 
fissure  are  large  openings  or  depressions,  which  transmit  blood-vessels, 
with  lymphatics  and  nerves,  to  and  from  the  interior  of  the  organ.  In 
some  cases  there  is  no  distinct  fissure,  but  merely  a row  of  openings 
for  the  vessels;  and  in  others  the  situation  of  the  hilus  is  occupied  by 
a longitudinal  ridge,  interrupted  by  the  vascular  orifices.  Two  layers 
of  peritoneum,  reflected  from  the  spleen,  at  the  borders  of  the  hilus, 
on  to  the  great  cul-de-sac  of  the  stomach,  and  containing  between 
them  the  splenic  vessels  and  nerves  and  the  vasa  brevia,  constitute  the 


STRUCTURE  OF  SPLEEN. 


497 


gastro-splenic  omentum  (ligamentum  gastro-lienale),  which  thus  serves 
to  attach  the  spleen  to  the  cardiac  end  of  the  stomach.  In  front  of  the 
gastro-splenic  omentum,  the  concave  face  of  the  spleen  is  smooth, 
invested  with  peritoneum,  and  is  closely  applied  to  the  stomach  ; the 
posterior  portion  of  that  face,  situated  behind  the  ligament  and  hilus, 
is  in  contact  with  the  left  pillar  of  the  diaphragm  and  the  corresponding 
supra-renal  capsule.  The  tail  of  the  pancreas  touches  the  lower  end 
of  the  inner  surface  of  the  spleen. 

The  anterior  margin  of  the  spleen,  w'hich  is  free,  and  curved  so  as 
to  be  applied  to  the  stomach,  is  thin,  and  often  slightly  notched,  espe- 
cially towards  its  lower  part.  The  posterior  border  and  upper  end 
are  thick  or  rounded,  and  rest  against  the  left  kidney  and  the  dia- 
phragm. To  the  former  the  spleen  adheres  by  loose  cellular  tissue ; 
and  to  the  latter  it  is  attached  by  a reflection  of  the  peritoneum, 
named  the  suspensory  ligament  (ligamentum  phrenico-lienale).  The 
lower  end  is  pointed,  and  is  in  contact  with  the  left  end  of  the  arch 
of  the  colon,  or  with  the  transverse  mesocolon. 

As  the  spleen  is  attached  by  the  gastro-splenic  omentum  to  the  sto- 
mach, and  by  the  suspensory  ligament  to  the  diaphragm,  its  position 
in  the  abdomen  is  necessarily  changed  by  the  movements  of  those 
parts.  Thus,  during  expiration  and  inspiration,  it  rises  and  falls  with 
the  diaphragm, — not,  how'ever,  descending  below  the  margins  of  the 
ribs,  when  of  its  ordinary  size. 

The  spleen  varies  in  magnitude  more  than  any  other  organ  in  the 
body  ; and  this  not  only  in  different  subjects,  but  in  the  same  indi- 
vidual, under  different  conditions — sometimes  appearing  shrunk,  and 
at  others  being  much  distended.  On  this  account  it  is  difficult  or  im- 
possible to  state  what  are  its  ordinary  weight  and  dimensions:  in  the 
adult  it  is  generally  about  5 or  bh  inches  from  the  upper  to  the  lower 
end,  3 or  4 inches  from  the  anterior  to  the  posterior  border,  and  1 or 
\h  inch  from  its  external  to  its  internal  surface;  and  its  usual  volume, 
according  to  Krause,  is  from  93  to  15  cubic  inches.  In  the  greater 
number  of  a series  of  cases  examined  by  Dr.  John  Reid,  its  weight 
ranged  from  5 to  7 oz.  in  the  male,  and  was  somewhat  less  in  the 
female;  but  even  when  perfectly  free  from  disease,  it  may  fluctuate 
between  4 and  10  oz.  After  the  age  of  forty  the  average  weight 
gradually  diminishes.  The  specific  gravity  of  this  organ,  according 
to  Haller,  Soemmerring,  and  Krause,  is  about  T060  to  1-000.  In  in- 
termittent and  in  other  fevers  the  spleen  is  much  distended  and  en- 
larged, reaching  below  the  ribs,  and  weighing  as  much  as  18  or  20 
lbs.  In  enlargement  and  solidification  of  this  organ,  it  has  been  known 
to  weigh  upw'ards  of  40  lbs.;  and  it  has  been  found  reduced  by  atrophy 
to  tw'o  drachms. 

Structure. — The  spleen  has  two  membranous  investments, — a serous 
coat  derived  from  the  peritoneum,  and  a special  albugineous  fibro- 
elastic  tunic.  The  substance  of  the  organ,  which  is  very  soft  and 
easily  lacerated,  is  of  a dark  reddish  brown  colour,  but  acquires  a 
bright  red  hue  on  exposure  to  the  air.  Sometimes,  how'ever,  the  sub- 
stance of  the  spleen  is  paler,  and  has  a grayish  aspect.  It  also  varies 
in  density,  being  occasionally  rather  solid  though  friable.  The  sub- 

42* 


498 


SIZE  OF  SPLEEN. 


Stance  of  the  organ  consists  of  a reticular  framework  of  white  elastic 
bands,  of  an  immense  proportion  of  blood-vessels,  the  larger  of  which 
run  in  elastic  canals,  and  of  a peculiar  intervening  pulpy  substance, 
besides  lymphatic  vessels  and  nerves.  As  previously  mentioned,  it 
has  no  system  of  ducts. 

The  external  serous  or  peritoneal  coat  is  thin,  smooth,  and  firmly 
adherent  to  the  elastic  tunic  beneath,  but  it  may  be  detached  by  care- 
ful dissection,  commencing  at  the  borders  of  the  hilus.  It  forms  only 
a partial  covering  for  the  spleen,  for  though  it  closely  invests  the  free 
surface  of  this  organ,  it  is  wanting  opposite  the  hilus  and  at  the  poste- 
rior border,  where  the  peritoneum  is  reflected  from  the  spleen  on  to 
the  stomach  and  diaphragm. 

The  internal,  elastic,  or  proper  tunic  is  much  thicker  and  stronger 
than  the  serous  coat,  unlike  which  it  covers  the  entire  surface  of  the 
organ.  It  is  whitish  in  colour,  and  is  composed  of  interlaced  bundles 
of  cellular  tissue  mixed  with  a fine  elastic  tissue.  In  addition  to  these 
there  are  found,  especially  in  the  bullock’s  spleen,  pale  soft  fibres,  ap- 
parently plain  or  unstriped  muscular  fibres,  resembling  those  of  the 
middle  coat  of  arteries.*  This  elastic  tunic  cannot  be  raised  from  the 
spleen,  because  numerous  bands  or  prolongations  pass  from  its  in- 
ternal surface  into  the  substance  of  the  organ.  Along  the  hilus  this 
coat  is  reflected  into  the  interior  of  the  spleen,  in  the  form  of  elastic 
sheaths  or  canals,  which  surround  or  include  the  large  blood-vessels 
and  nerves,  and  their  principal  branches.  Stretching  across  in  all 
directions  between  these  sheaths,  and  traversing  the  intermediate  sub- 
stance of  the  spleen,  are  multitudes  of  small  elastic  bands,  named 
trabeculcB  (diminutive  of  trabs,  a beam);  many  of  these  bands,  more- 
over, are  attached  to  the  internal  surface  of  the  proper  tunic  of  the 
spleen,  which  they  exactly  resemble  in  structure,  and  of  which  they 
form  the  inward  prolongations  just  spoken  of.  The  proper  coat,  the 
sheaths  of  the  vessels,  and  the  trabeculae  being  all  of  a highly  elastic 
nature,  constitute  a distensible  framework,  which  contains  in  its  inter- 
stices or  areolae  the  vessels  and  the  red  pulpy  substance  of  the  spleen. 

It  is  owing  to  this  structure,  endowed  perhaps  with  vital  contracti- 
lity as  well  as  mere  elasticity,  that  the  organ  is  capable  of  such  great 

• The  statement  in  the  text  is  founded  on  what  I had  observed  more  than  two  years  ago, 
and  have  since  been  in  the  habit  of  mentioning  in  my  lectures.  The  observation,  however, 
was  not  followed  up.  Since  the  above  was  in  type,  I have  received  from  Professor  Kolliker 
a paper  (from  the  “ Mittheilungen  der  Zilrcher  naturforschenden  Gesellchaft,”  for  June, 

1847)  containing  the  results  of  investigations  made  by  him  into  the  structure  of  the  spleen 
in  many  different  animals,  from  which,  without  being  aware  of  my  observation,  he  arrives 
at  the  conclusion  that  the  spleen  is  a “muscular  organ.”  The  muscular  fibres  are  of  the 
plain  variety,  and  mixed  with  elastic  or  nuclear  fibres.  In  some  animals,  as  the  pig,  dog, 
and  cat,  they  exist  in  the  allugineous  or  proper  coat,  the  sheaths  of  the  vessels  and  the  tra-  i 

beculoB  ; in  the  rabbit  they  are  wanting  in  the  coat,  and  in  the  ox,  according  to  Kolliker,  ^ 

they  aie  found  only  in  the  small-sized  and  microscopic  trabeculae,  the  rest  of  the  trabecular  | 

structure  and  proper  coat  consisting  merely  of  elastic  and  cellular  tissue.  He  finds  that  i 

the  muscular  tissue  of  the  spleen  is,  for  the  most  part,  made  up  of  short,  flat,  pale  fibres,  | 

from  to  inch  long,  bearing  oblong  nuclei.  As  to  the  human  spleen,  he  could  dis-  ' 
cover  muscular  structure  neither  in  the  proper  coat,  nor  in  the  larger  traheculas ; but  the 
fine  microscopic  trabeculas  appeared  to  be  made  up  of  elongated  cells,  with  round  nuclei, 
which  he  is  disposed  to  regard  as  elements  constituting  a muscular  tissue.  He  could  ob- 
tain no  unequivocal  evidence  of  contraction  on  irritating  the  spleen  in  recently  killed  pni- 
mals. — W.  S. 


CORPUSCLES  OF  SPLEEN. 


499 


and  sudden  alterations  of  size.  The  arrangement  of  the  elastic 
sheaths  and  trabeculae  may  be  easily  displayed  by  pressing  and  wash- 
ing out  the  intervening  substance. 

The  splenic  artery  and  vein,  alike  remarkable  for  their  great  pro- 
portionate size,  having  entered  the  spleen  by  six  or  more  branches, 
ramify  in  its  interior,  enclosed  within  the  elastic  sheaths  already 
described.  The  smaller  branches  of  the  arteries  run  along  the  tra- 
beculae, and  terminate  in  the  proper  substance  of  the  spleen  in  small 
tufts  or  pencils  of  capillary  vessels.  The  veins,  which  greatly  exceed 
the  arteries  in  size,  anastomose  frequently  together,  so  as  to  form  a 
close  venous  plexus,  placed  in  the  intervals  between  the  trabeculae, 
and  supported  by  them.  It  is  stated  by  Krause  that  the  veins  form 
numerous  lateral  dilatations  or  diverticula,  which  communicate  with 
the  general  plexus,  and  the  walls  of  which  are  formed  principally  by 
the  lining  membrane  of  the  veins.  Each  large  vein  also  receives  in 
its  course  many  small  branches,  the  orifices  of  which  give  a dotted 
appearance  to  the  interior  of  the  vein.  From  the  facility  with  which 
fluid  injections  pass  from  the  arteries  into  the  veins,  the  communica- 
tion between  the  two  sets  of  vessels  must  be  very  free;  but  the  mode 
in  which  it  takes  place  is  not  yet  determined. 

The  ■proper  substance  of  the  spleen  is  a soft  pulpy  mass,  of  a dark 
reddish  brown  colour,  which,  when  squeezed  out  from  between  the 
trabeculae,  resembles  grumous  blood,  and,  like  that  fluid,  acquires  a 
brighter  hue  on  exposure  to  the  air.  I’his  pulpy  substance  lies  alto- 
gether outside  the  veins,  between  the  branches  of  the  venous  plexus. 
As  shown  by  the  microscope,  it  consists  chiefly  of  numerous  rounded 
granular  bodies,  which  have  a reddish  colour,  and  are  about  the  size 
of  the  blood  corpuscles.  Their  cohesion  is  very  slight,  and  the  termi- 
nal tufts  of  the  arterial  system  of  vessels  spread  out  amongst  them. 
In  examining  the  substance  of  the  spleen,  elongated  caudate  corpuscles 
are  seen  in  rather  large  numbers. 

On  closely  inspecting  the  surface  of  a section  of  the  spleen,  a num- 
ber of  white  spots  of  variable  size  are  always  seen.  For  the  most 
part  these  are  evidently  the  ends  of  divided  trabeculte  or  blood-ves- 
sels ; but  in  the  ox,  pig,  sheep,  and  some  other  animals,  and  also,  too,  in 
the  human  subject,  there  are  found  distinct  white  vesicular  bodies  at- 
tached to  the  trabecultB,  which  support  the  small  arteries,  and  em- 
bedded in  groups  of  six  or  eight  together  in  the  dark  red  substance  of 
the  spleen.  These  little  vesicles  or  capsules,  formerly  known  as  the 
Malpighian  corpuscles  of  the  spleen,  were  discovered  in  the  pig  by 
Malpighi,  who  thought  they  were  situated  within  the  veins.  They  are 
rounded  capsules,  varying  in  diameter  from  ^^th  to  g’gth  of  an  inch, 
and  consisting  of  two  coats,  the  external  apparently  continuous  with 
the  trabecular  tissue  supporting  the  arteries.  They  are  filled  with  a 
soft,  white,  semi-fluid  matter,  which  contains  microscopic  globules, 
resembling,  except  in  colour,  those  composing  the  red  pulp  of  the 
spleen.  It  may  be  remarked,  that  both  these  kinds  of  globules  are 
very  like  the  chyle  corpuscles. 

These  capsules  are  attached  in  groups  to  the  smaller  vascular 
sheaths  or  trabeculae,  by  the  minute  branches  of  a small  artery,  which 


500 


THE  PERITONEUM. 


is  itself  supported  by  the  elastic  sheath  or  band.  In  some  of  the  lower 
animals  they  are  sessile,  but  in  the  human  spleen  they  are  peduncu- 
lated. The  arterial  capillaries  do  not  penetrate  them,  but  appear  to 
form  around  them  a sort  of  vascular  coat  or  envelope.  It  has  been 
conjectured  by  some  that  these  vesicular  bodies  are  dilatations  of  the 
lymphatics  of  the  spleen,  but  their  true  nature  and  connexions  are  not 
yet  ascertained. 

The  lymphatic  vessels  of  the  spleen  are  very  abundant,  and  form  a 
superficial  and  deep  set.  The  superficial  set  appear  as  a network 
beneath  the  serous  coat,  receive  occasional  branches  from  the  sub- 
stance of  the  spleen,  and  run  towards  the  hilus.  The  deep  lymphatics 
accompany  the  blood-vessels,  and  emerge  with  them  at  the  hilus, 
whence,  communicating  with  the  superficial  set,  they  proceed  along 
the  gastro-splenic  omentum  to  the  neighbouring  lymphatic  glands. 
The  mode  in  which  the  lymphatics  commence  in  the  spleen  is  un- 
known. 

The  splenic  nerves  derived  from  the  solar  plexus  surround  and  ac- 
company the  splenic  artery  and  its  branches.  They  have  been  traced 
by  Remak  deeply  into  the  interior  of  the  organ. 

Development. — The  spleen  appears  in  the  fetus,  about  the  seventh  or  eighth 
week,  on  the  left  side  of  the  dilated  part  of  the  alimentary  tube,  or  stomach,  and 
close  to  the  rudiment  of  the  pancreas.  By  the  tenth  week  it  forms  a distinct 
lobulated  body  placed  at  the  great  end  of  the  stomach.  After  birth  it  increases 
rapidly  in  size ; and  in  comparison  with  the  weight  of  the  body,  it  is  as  heavy 
a few  weeks  after  birth  as  in  the  adult.  This  organ  is  peculiar  to  vertebrate 
animals. 

Small  detached  roundish  nodules  are  occasionally  found  in  the  neighbourhood 
of  the  spleen,  similar  to  it  in  substance.  These  are  commonly  named  accessory 
or  sapp/cTuentary  spleens  (splenculi;  lienculi).  One  or  two  is  the  most  common 
number,  but  four,  seven,  and  even  twenty-three  have  been  met  with  in  one  sub- 
ject. They  are  small  rounded  masses,  varying  from  the  size  of  a pea  to  that  of 
a walnut.  They  are  usually  situated  near  the  lower  end  of  the  spleen,  either  in 
the  gastro-splenic  omentum,  or  in  the  great  omentum.  These  separate  splenculi 
in  the  human  subject  bring  to  mind  the  multiple  condition  of  the  spleen  in  some 
animals,  and  also  the  notching,  often  deep,  of  the  anterior  margin  of  this  organ 
in  man. 

Uses. — The  function  of  the  spleen  is  unknown.  Besides  any  mechanical  office 
it  may  perform,  as  a diverticulum  for  the  blood,  it  is  thought  by  many  to  be  con- 
cerned in  the  formation  of  that  fluid.  It  has  been  imagined  to  be  an  appendage 
of  the  lymphatic  system ; and  it  has  also  been  supposed  to  assist  in  preparing 
blood  for  the  secretion  of  the  bile.  But  it  would  be  useless  to  recount  all  the 
various  hypotheses  which  have  been  at  different  times  entertained  respecting  its 
offices.* 

THE  PERITONEUM. 

The  common  cavity  of  the  abdomen  and  pelvis  is  lined  by  a serous 

* Kolliker  is  led  to  infer  from  his  observations  that  the  blood  corpuscles  suffer  destruc- 
tion, or  at  least  decomposition,  in  the  spleen.  He  supposes  that  they  deerease  in  size, 
group  together  in  round  clumps,  which  acquire  nuclei  and  envelopes,  so  as  to  constitute 
cells  filled  with  altered  blood  corpuscles;  that  the  substanee  of  the  contained  blood  corpus- 
cles is  then  resolved  into  pigment  granules,  of  a golden  yellow,  brown  or  black  colour,  and 
that  the  eells  may  thus  remain  or  become  blanched  into  colourless  cells  very  much  resera- 
bling  the  pale  corpuscles  of  the  blood.  He  is  uncertain  how  they  are  finally  disposed  of. — 
(See  his  paper  already  quoted.) 


THE  PERITONEUM. 


501 


membrane,  named  the  peritoneum  (fs^irsivu) , which  is  reflected  over 
the  contained  viscera.  It  is  the  most  extensive  and  complicated  of  all 
the  serous  membranes,  and  like  them  it  forms  a shut  sac,  on  the  out- 
side of  which  are  placed  the  viscera  which  it  covers.  In  the  female, 
however,  it  is  not  completely  closed,  for  the  two  Fallopian  tubes  at 
their  free  extremity  open  into  the  cavity  of  the  peritoneurh.  The  in- 
ternal surface  of  the  peritoneal  membrane  is  free,  smooth,  and  moist, 
and  is  covered  by  a thin  squamous  epithelium  (fig.  274,  p.  60).  Its 
external  or  attached  surface  adheres  partly  to  the  inner  walls  of  the 
abdomen  and  pelvis,  and  partly  to  the  outer  surface  of  the  viscera 
situated  within  them.  The  former  part,  named  the  parietal  portion, 
is  connected  loosely  with  the  fasciae  lining  the  abdomen  and  pelvis, 
but  more  firmly  along  the  middle  line  of  the  body  in  front,  as  well  as 
to  the  under  surface  of  the  diaphragm.  This  connexion  takes  place 
by  means  of  a cellular  layer,  distinct  from  the  abdominal  fasciae,  and 
named  the  sub-peritoneal  or  retro-peritoneal  membrane.  The  visceral 
portion,  which  is  thinner  than  the  other,  forms  a more  or  less  perfect 
investment  to  the  abdominal  and  pelvic  viscera.  Some  of  these 
organs,  as  the  liver,  spleen,  stomach,  and  small  intestine,  (except  the 
duodenum,)  the  transverse  colon,  sigmoid  flexure,  upper  end  of  the 
rectum,  and  the  uterus  and  ovaries,  are  almost  entirely  surrounded  by 
peritoneum.  Others  receive  only  a partial  covering  from  it,  as  the 
two  lower  portions  of  the  duodenum,  the  caecum,  the  ascending  and 
descending  colon,  the  middle  portion  of  the  rectum,  and  the  upper 
part  of  the  vagina  and  bladder.  Over  a few  parts,  the  peritoneum 
passes  without  forming  any  distinct  coat  for  them,  as  the  pancreas, 
supra-renal  capsules,  and  kidneys.  Lastly,  the  lower  end  of  the  rec- 
tum, the  base  and  neck  of  the  bladder,  the  prostate  in  the  male  and 
the  low’er  part  of  the  vagina  in  the  female,  have  no  peritoneal  invest- 
ment. 

Folds. — Besides  covering  the  viscera,  the  peritoneum  forms  nume- 
rous duplicatures,  which  not  only  serve  as  means  of  attachment  and 
support  to  the  various  organs,  but  also  enclose  the  vessels  and  nerves 
of  each  part,  as  they  pass  to  and  from  the  back  part  of  the  abdomen. 
Some  of  these  folds,  constituting  the  mesenteries,  connect  certain  por- 
tions of  the  intestinal  canal  with  the  posterior  wall  of  the  abdomen : 
they  are,  the  mesentery  properly  so  called  for  the  jejunum  and  ileum, 
the  meso-cascum,  transverse  and  sigmoid  meso-colon,  and  the  meso- 
rectum.  Other  duplicatures,  which  are  called  omenta,  proceed  from 
one  viscus  to  another : they  are  distinguished  as  the  great  omentum, 
the  small  omentum,  and  the  gastro-splenic  omentum.  Lastly,  certain 
reflections  of  the  peritoneum  from  the  walls  of  the  abdomen  or  pelvis 
to  viscera  which  are  not  portions  of  the  intestinal  canal,  are  named 
ligaments:  these  include  the  ligaments  of  the  liver,  spleen,  uterus,  and 
bladder,  and  are  elsewhere  described  with  the  organs  to  which  they 
are  respectively  attached. 

Omenta. — The  great  omentum,  gastro-colic  omentum,  or  great  epi- 
ploon (g'TTi'TrXsw ; fig.  246,  7),  is  a broad  process  of  peritoneum  which 
depends  from  the  lower  border  of  the  stomach  and  the  transverse 


502 


THE  PERITONEUM. 


colon,  and  below  that  point  lies  free,  in  front  of  the  convolutions  of 
the  small  intestine,  reaching  nearly  as  low  down  as  the  pelvis.  On 
the  left  the  great  epiploon  is  continuous  with  the  gastro-splenic  omen- 
tum : to  the  right  it  reaches  only  to  the  duodenum.  At  its  upper 
border,  which  is  concave,  and  attached  to  the  great  curvature  of  the 
stomach,  it  consists  of  two  coherent  layers  of  serous  membrane, 
descending,  one  from  the  front,  the  other  from  the  back  of  the  sto- 
mach (fig.  474,  s).  These  two  layers  (®)  applied  one  to  the  other, 
descend  to  the  lower  convex  limit  of  the  omentum,  which  hangs  freely 
in  the  abdomen,  and  there  turning  upwards,  ascend  to  be  attached 
along  the  transverse  colon  (c),  becoming  continuous  with  its  perito- 
neal coat;  hence  the  name,  gastro-colic  omentum.  In  its  lower  free 
portion,  that  is,  below  the  colon,  it  therefore  comprehends  in  its  thick- 
ness four  layers  of  peritoneum,  two  ascending  and  two  descending. 
This  maybe  demonstrated  in  young  subjects:  in  the  adult  the  two 
double  layers  become  inseparably  united.  The  compound  structure 
thus  formed  is  very  thin,  and  is  sometimes  perforated  with  holes  like 
lace.  It  always  contains  some  adipose  tissue,  and  in  fat  subjects  it  is 
much  loaded.  Large  vessels  descending  from  the  gastro-epiploic 
arteries  supply  it  with  blood. 

The  small  or  gastro-hepatic  omentum,  the  small  epiploon,  is  a dupli- 
cature  of  the  peritoneum,"*  which  extends  from  the  lesser  curvature  of 
the  stomach  to  the  transverse  fissure  and  to  the  fossa  of  the  ductus 
venosus,  on  the  under  surface  of  the  liver,  and  encloses  the  hepatic 
vessels  and  ducts.  At  the  left  border  of  this  omentum  its  two  layers 
pass  on  to  the  end  of  the  oesophagus;  but  at  the  right  border  they 
become  continuous  with  each  other,  so  as  to  form  a free  rounded 
margin,  and  enclose  the  vena  porlse,  the  hepatic  artery,  and  the  biliary 
duct.  Behind  this  free  margin  with  its  contained  vessels,  in  front  of 
the  ascending  vena  cava,  and  immediately  below  the  Spigelian  lobe 
of  the  liver,  is  an  opening  or  short  canal,  named  the  foramen  of 
Winslow.  This  canal  leads  down  behind  the  stomach  into  a space 
named  the  sac  of  the  omentum.  This  space,  which  may  be  shown  by 
holding  the  parts  asunder,  is  therefore  placed  behind  the  small  omen- 
tum and  below  the  liver:  it  extends  downwards  between  the  posterior 
surface  of  the  stomach  and  the  upper  or  ascending  layer  of  the  trans- 
verse mesocolon.  In  young  subjects,  by  forcing  air  into  the  foramen 
of  Winslow,  the  continuance  of  this  sac  is  further  shown  between  the 
two  descending  and  the  two  ascending  lamellse  of  the  great  omentum, 
down  to  the  lower  border  of  that  process  of  the  peritoneum.  Its 
smooth  lining  membrane  is  continuous  with  the  rest  of  the  peritoneum 
at  the  foramen  of  Winslow,  which  is  therefore  not  a perforation  in 
the  peritoneum. 

The  gastro-splenic  omentum  {or  ligament)  is  another  duplicature, 
which  passes  from  the  cul-de-sac  of  the  stomach  to  the  borders  of  the 
hilus  of  the  spleen.  It  contains  the  splenic  vessels  and  the  yasa 
brevia.  At  its  right  or  lower  margin  it  is  continuous  w'ith  the  great 
omentum. 

Mesenteries. — The  mesentery  proper  is  that  large  and  important 


THE  PERITONEUM. 


503 


diiplicature  of  the  peritoneum  which  is  attached  by  its  posterior 
border  to  the  front  of  the  vertebral  column,  and  is  connected  along  its 
anterior  border  with  the  convolutions  of  the  jejunum  and  ileum.  Its 
attachment  to  the  vertebral  column,  named  the  root  of  the  mesentery, 
is  not  more  than  six  inches  long,  and  extends  in  an  oblique  line  from 
the  left  side  of  the  second  lumbar  vertebra  to  the  right  sacro-iliac 
symphysis.  At  its  upper  end  this  border  of  the  mesentery  receives  the 
superior  mesenteric  vessels,  and  is  continuous  with  the  under  surface 
of  the  transverse  meso-colon ; at  the  lower  end  it  gradually  spreads 
into  the  peritoneum  of  the  ascending  colon,  The  anterior  border  of 
the  mesentery,  to  which  the  intestine  is  attached,  is  of  much  greater 
length. 

At  its  widest  part  the  mesentery  is  about  four  inches  from  its  verte- 
bral to  its  intestinal  border.  Between  the  two  layers  of  serous  mem- 
brane of  which  it  consists  are  placed,  besides  some  fat,  numerous 
branches  of  the  superior  mesenteric  artery  and  vein,  together  with 
nerves,  lacteal  vessels,  and  the  mesenteric  glands  (see  p.  44).  In 
front,  the  two  layers  open  out,  as  it  were,  to  embrace  the  intestinal 
tube,  and  become  continuous  along  its  free  border,  thus  forming  its 
peritoneal  covering. 

Meso-ccBcum. — In  some  cases  the  caecum  is  suspended  at  a short 
distance  from  the  right  iliac  fossa,  by  a distinct  duplicature  of  the 
peritoneum,  which  is  termed  the  meso-caecum  ; but,  more  commonly, 
the  peritoneum  merely  binds  down  this  part  of  the  large  intestine, 
and  forms  a distinct  but  small  mesentery  for  the  vermiform  appendix 
only. 

Meso-colon. — The  ascending  and  descending  portions  of  the  colon 
are  bound  down  by  the  peritoneum,  which  usually  passes  only  over 
the  front  and  sides  of  the  intestine,  but  sometimes  forms  a narrow 
duplicature  behind  them,  named  ascending  or  descending  meso-colon. 
The  transverse  part  of  the  colon,  however,  is  always  supported  by  a 
very  broad  duplicature,  named  the  transverse  meso-colon.  This  is,  in 
fact,  formed  by  the  continuation  backwards  of  the  two  ascending 
layers  of  the  great  omentum,  which,  after  reaching  the  front  of  the 
transverse  colon,  separate  so  as  to  enclose  that  intestine,  and,  meeting 
again  behind  it,  are  continued  backwards  (as  the  transverse  meso- 
colon) to  the  spine.  Here  its  two  layers  diverge,  one  continuing 
upwards  over  the  pancreas,  and  the  other  downwards  over  the  trans- 
verse portion  of  the  duodenum,  both  these  organs  thus  obtaining  a 
partial  peritoneal  covering.  The  peritoneum  forms  rather  a broad 
duplicature  behind  the  freely  suspended  sigmoid  flexure  of  the  colon. 

The  Meso-rectum  is  a narrow  duplicature  which  connects  the  upper 
part  of  the  rectum  with  the  sacrum. 

The  way  in  which  the  peritoneum  is  reflected  from  the  walls  of  the  abdomen 
and  from  one  organ  to  another,  and  the  mode  in  which  its  numerous  duplicatures 
are  formed,  may  now  be  traced  consecutively.  Commencing  at  the  small  omen- 
tum (fig.  474,  as  a starting-point,  that  Structure  will  be  found  to  consist  of  two 
layers  of  the  serous  membrane.  Of  these  we  shall  first  follow  the  upper  or 
anterior,  and  then  the  lower  or  posterior  layer.  1.  The  upper  layer  may  be  traced 
to  the  small  curvature  of  the  stomach  (s),  and  then  over  the  anterior  surface 


604 


THE  PERITONEUM. 


[Fiff.  474. 


of  that  organ  as  far  as  the  great  curva- 
ture ; from  this  it  reaches  down,  forming 
the  outermost  layer  of  the  great  omentum 
at  the  lower  border  of  which  it 
becomes  reliected  upwards,  and  ascends 
to  the  transverse  colon  (c)  ■ having  in- 
vested the  under  surface  of  this  part  of 
the  large  intestine,  it  passes  backwards, 
forming  the  under  layer  of  the  transverse 
meso-colon  (’),  and  reaches  the  back 
of  the  abdominal  cavity  beneath  the 
transverse  part  of  the  duodenum  (u). 
Below  this  point  it  is  continued  on 
either  side  to  the  right  and  left  colon, 
and  thus  on  to  the  anterior  wall  of  the 
abdomen,  whilst  in  the  middle  it  is 
prolonged  forwards  from  the  spine  to 
the  small  intestine  (i),  after  investing 
which,  it  returns  to  the  front  of  the 
spine,  and  thus  completes  the  mesentery 
('“),  which,  as  elsewhere,  mentioned, 
consists  of  two  contiguous  layers.  From 
the  root  of  the  mesentery  it  descends 
in  front  of  the  spine,  and  partially 
invests  the  rectum  (r),  the  uterus,  and 
the  bladder  (b),  forming  folds  at  the 
points  of  reflection  from  one  organ  to 
another,  as  is  elsewhere  more  particu- 
larly described.  From  the  summit  of 
the  bladder  it  is  prolonged  to  the  ante- 
rior wall  of  the  abdomen  (”),  and  then 
continues  to  ascend  as  high  as  the  costal 
cartilages,  where  it  comes  into  con- 
tact with  the  diaphragm  (u),  and  lines 

rr,.  n f ,,  r.  rnu  the  under  surface  of  that  muscle.  From 

Ine  refleclions  of  the  peritoneum.-  D.  The  i r 

diaphragm.  S.  The  stomach.  C.  The  transverse  diaphragm,  the  layer  of  peritoneum 
colon.  D.  The  transverse  dundemim.  P.  The  We  are  now  tracing  is  reflected  upon 
pancreas.  1.  The  small  intestines.  R.  The  the  liver  at  **,  forming  its  lateral  and  the 
rectum.  B.  The  urinary  bladder.  1.  The  upper  layer  of  its  coronary  ligamenfs  : 

anterior  layer  of  the  peritoneum,  lining  the  u dpanhes  the  liver  too  as  the  susnen- 
under  surface  of  the  diaphragm,  2.  The  pos-  “ reacnes  tno  liver,  100,  as  me  suspen 

terior  layer.  3.  The  coronary  ligament,  formed  sory  or  broad  hgament,  a nearly  median 
by  the  passage  of  these  two  layers  to  the  poste-  duplicature  passing  off  from  the  right 
nor  border  of  the  liVer.  4.  The  lesser  omentum  ; rectus  muscle  and  diaphragm ; it  next 
the  two  layers  passing  from  the  under  surlace  of  invests  the  upper  and  then  the  under 
!ne  iiver  to  the  lesser  curve  ot  Ihe  stomacli.  5.  r r .a.  v / \ r +1.^ 

The  two  layers  meeting  at  the  greater  curve,  ^'^rf^ce  of  the  liver  (l),  as  far  as  the 

then  passing  downwards  and  reluming  upon  transverse  fissure,  where  it  IS  reflected 
themselves,  forming  (6)  the  greater  omenliim.  7.  down  upon  the  hepatic  vessels,  forming 
The  transverse  tne'so-colon.  8.  The  posterior  the  upper  or  anterior  layer  of  the  small 
layer  traced  upwards  in  front  of.  D,  the  trans-  omentum  M,  from  which  we  began  to 
verse  duodenum,  and  1,  the  pancreas,  to  become  ^ v,  ..  „ me  ; 

continuous  with  the  posterior  layer  (2).  9.  The  reflections.  2.  The  under  or 

foramen  of  Winslow ; the  dotted  line  bounding  posterior  layer  of  the  small  omentum 
this  foramen  inferiorly  marks  the  course  of  the  may  be  traced  to  the  small  curvature  of 
hepatic  artery  forwards,  to  enter  between  the  the  Stomach,  and  thence  along  the  pos- 
10- The  mesentery  ^ f f ^^3  jtg 

encircling  the  small  intestine.  11.  The  redo-  „ , • • 

vesical  fbld,  formed  by  the  descending  anterior  great  curvature;  from  this  point  the  mem- 
layer.  12.  The  anterior  layer  traced  upwards  brane  reaches  down,  forming  the  inner- 
upon  the  internal  surface  of  the  abdominal  most  layer  of  the  great  omentum  (°), 
parietes  to  the  layer  (It,  with  which  the  exami-  ^he  lower  border  of  which  it  is  refle.Ct- 
iialion  commenced. — W.]  i i 

■'  ed  up  to  the  transverse  colon  (c) : alter 

investing  the  upper  surface  of  this  part  of  the  large  intestine,-  it  is  reflected  back 
towards  the  spine,  forming  the  upper  layer  of  the  transverse  meso-colon  (®) ; it 


REGIONS  OF  ABDOMEN. 


505 


is  thence  prolonged  in  front  of  the  pancreas  (p)  and  the  crura  of  the  diaphragm : 
from  the  under  surface  of  the  diaphragm  it  is  reflected  on  to  the  liver  at  and 
helps  to  form  the  under  layer  of  its  coronary  ligament;  having  invested  the  under 
surface  of  the  liver  as  far  as  the  transverse  fissure,  it  is  there  reflected  down- 
wards, and  forms  the  under  or  posterior  layer  of  the  small  omentum  (■»),  from 
which  we  commenced  the  description,  and  the  right  border  of  which,  being  free, 
forms  the  anterior  margin  of  the  foramen  of  Winslow.  In  ascending  along  the 
back  of  the  abdominal  cavity  to  the  liver,  this  posterior  layer  passes  to  the  right 
over  the  vena  cava,  and  there  bounds  the  foramen  of  Winslow  behind,  and  still 
further  to  the  right  becomes  continuous  with  the  general  peritoneal  membrane. 

The  peritoneum  may,  of  course,  also  be  traced  continuously  from  any  other 
point  of  its  surface. 

Vessels  and  nerves. — ^The  vessels  and  nerves  of  the  peritoneum  are  derived  from 
many  sources.  Its  internal  surface  is  moistened  with  a thin  fluid.  It  serves  to 
attach  or  suspend  the  viscera,  to  support  their  vessels  and  nerves,  and,  where 
that  is  required,  to  facilitate  their  movements  on  each  other. 


PARTS  SITUATED  IN  EACH  REGION  OF  THE  ABDOMEN. 


Subjoined  is  an  enumeration  of  the  organs  situated  in  the  different 
regions  of  the  abdomen. 


Epigastric  region 


Hypochondriac,  right 


Hypochondriac,  left 


Umbilical  . . 

Lumbar,  right 
Lumbar,  left  . 

Hypogastric  . 

Iliac,  right 
Iliac,  left  . . 


The  middle  part  of  the  stomach,  with 
its  pyloric  extremity,  the  left  lobe  of 
the  liver,  the  hepatic  vessels,  and  lobu- 
lus  Spigelii,  the  pancreas,  the  cceliac 
axis,  the  semilunar  ganglia,  part  of  the 
vena  cava,  also  of  the  aorta,  vena 
azygos  and  thoracic  duct,  as  they  lie 
between  the  crura  of  the  diaphragm. 

The  right  lobe  of  the  liver  with  the 
gall-bladder,  part  of  the  duodenum, 
the  hepatic  flexure  of  the  colon,  the 
right  suprarenal  capsule,  and  part  of 
the  corresponding  kidney. 

The  large  end  of  the  stomach  with  the 
spleen  and  narrow  extremity  of  the 
pancreas,  the  splenic  flexure  of  the 
colon,  the  left  suprarenal  capsule,  and 
upper  part  of  the  left  kidney.  Some- 
times also  a part  of  the  left  lobe  of 
the  liver. 

Part  of  the  omentum  and  mesentery, 
the  transverse  part  of  the  colon,  trans- 
verse part  of  the  duodenum,  with 
some  convolutions  of  the  ieiunum  and 
ileum. 

Ascending  colon,  lower  half  of  the 
kidney,  and  part  of  the  jejunum. 

Corresponding  parts  at  the  opposite 
side. 

The  convolutions  of  the  ileum,  the 
bladder  in  children,  and,  if  distended, 
in  adults  also ; the  uterus  when  in  the 
gravid  state. 

The  caecum,  ileo-cascal  valve,  the  ureter, 
and  spermatic  vessels. 

Sigmoid  flexure  of  the  colon,  the  ureter, 
and  spermatic  vessels. 


43 


VOE.  II. 


THE  URINARY  ORGANS. 


The  urinary  organs  consist  of  the  kidneys,  by  which  the  urine  is 
secreted,  and  of  the  ureters,  bladder,  and  urethra,  which  are  concerned 
in  its  excretion  and  evacuation.  As  locally  connected,  the 
capsules  are  usually  described  with  these  organs,  though  they  have  no 
relation,  as  far  as  is  known,  to  the  secretion  of  urine. 

THE  KIDNEYS. 

The  kidneys  (renes,  vaqjpoi),  two  in  number,  one  right  and  the  other 
left,  are  deeply  seated  in  the  lumbar  region,  lying  one  on  each  side  of 
the  vertebral  column,  at  the  back  part  of  the  abdominal  cavity,  behind 
the  peritoneum.  They  are  situated  on  a level  with  the  last  dorsal  and 
the  two  or  three  upper  lumbar  vertebrae,  the  right  kidney  however 
being  placed  a little  lower  down  than  the  left,  probably  in  consequence 
of  the  vicinity  of  the  large  right  lobe  of  the  liver.  They  are  main- 
tained in  this  position  by  their  vessels,  and  also  by  a quantity  of  sur- 
rounding loose  cellular  tissue,  which  usually  contains  much  dense  fat. 
The  size  of  the  kidneys  varies  in  different  cases.  Ordinarily,  they 
measure  about  four  inches  in  length,  two  inches  in  breadth,  and  an 
inch  or  rather  more  in  thickness.  The  left  kidney  is  usually  longer 
and  thinner,  whilst  the  right  is  shorter  and  wider  in  proportion. 

Weight. — The  average  weight  of  the  kidney  is  usually  stated  to  be  about  4^ 
ozs.  in  the  male,  and  somewhat  less  in  the  female.  According  to  Dr.  Clendin- 
ning,*  the  two  kidneys  of  the  male  weigh  on  an  average  ozs.,  and  those  of  the 
female  9 ozs.  The  estimate  of  M.  Rayerf  is  4^  ozs.  for  each  organ  in  the  male, 
and  3|  ozs.  in  the  other  sex.  Dr.  J.  Reid’sf  observations  (made  on  sixty-five 
males  and  twenty-eight  females,  between  the  ages  of  twenty-five  and  fifty-five) 
would  indicate  a higher  average  weight,  viz.,  rather  more  than  5J  ozs.  in  the 
former,  and  not  quite  5 ozs.  in  the  latter, — the  difference  between  the  two  sexes 
being  therefore  upwards  of  half  an  ounce.  The  prevalent  weights  of  the  kidney, 
as  deduced  from  the  tables  of  Dr.  Reid,  are,  in  the  adult  male  (160  observations) 
from  4i  ozs.  to  6 ozs.,  and  in  the  adult  female  (74  observations)  from  4 ozs.  to  5| 
ozs.  The  tables  more  recently  published  by  Dr.  Peacock  give  still  higher  average 
results  as  to  the  weight  of  these  organs.  ( The  two  kidneys  are  seldom  of  equal 
weight,  the  left  being  almost  always  heavier  than  the  right.  The  difference, 
according  to  M.  Rayer,  is  equal  to  about  one-sixth  of  an  ounce.  The  actual 
average  difference  was  found  by  Dr.  Reid,  in  ninety-three  cases  (male  and 
female),  to  be  rather  more  than  one-fourth  of  an  ounce.  The  proportionate  weight 
of  the  two  kidneys  to  the  body  is  about  1 to  240.  The  specific  gravity  of  the  renal 
substance  is,  on  an  average,  1 052. 

The  surface  of  the  kidney  is  smooth  and  has  a deep  red  colour.  Its 
/brm  is  peculiar : it  is  compressed  before  and  behind,  convex  on  its 
outer  and  concave  on  its  inner  border,  and  somewhat  enlarged  at  its 
upper  and  lower  ends. 

* Loc.  cit.  t Traits  des  Mai.  des  Reins.  Paris,  1839.  t Loc.  cit.  § Loc.  cit. 


STRUCTURE  OF  THE  KIDNEYS. 


507 


The  anterior  surface,  more  convex  than  the  posterior,  is  directed 
somewhat  outwards,  and  is  partially  covered  at  its  upper  end  by  the 
peritoneum,  which  is  separated  from  it  lower  down  by  loose  cellular 
tissue.  The  duodenum  and  ascending  colon,  both  destitute  of  peri- 
toneum behind,  are  in  contact  with  the  anterior  surface  of  the  right 
kidney,  and  the  descending  colon  with  that  of  the  left.  The  front  of 
the  right  kidney,  moreover,  touches  the  under  surface  of  the  liver,  and 
that  of  the  left  the  lower  extremity  of  the  spleen.  The  posterior 
surface,  flatter  than  the  anterior,  and  embedded  in  cellular  tissue,  rests 
partly  upon  the  corresponding  pillar  of  the  diaphragm,  in  front  of  the 
eleventh  and  twelfth  ribs,  partly  on  the  quadratus  lumborum  muscle, 
or  rather  on  the  anterior  layer  of  the  lumbar  fascia,  which  covers  it, 
and  lastly,  on  the  psoas  muscle.  The  external  border,  convex  in  its 
general  outline,  is  directed  outwards  and  backwards  towards  the  walls 
of  the  abdomen.  The  internal  border,  concave  and  deeply  excavated 
towards  the  middle,  is  directed  a little  downwards  and  forwards.  It 
presents  in  its  middle  a longitudinal  fissure  bounded  by  an  anterior  and 
posterior  lip,  and  named  the  hilus  of  the  kidney,  at  which  the  vessels, 
the  excretory  duct,  and  the  nerves  enter  or  pass  out.  In  this  hilus, 
the  renal  vein  lies  in  front,  the  artery  and  its  branches  next,  and  the 
expanded  excretory  duct  or  ureter  behind  and  towards  the  lower  part 
of  the  hilus.  The  upper  end  of  the  kidney,  which  is  larger  than  the 
lower,  is  thick  and  rounded,  and  supports  the  supra-renal  capsule, 
which  also  descends  a little  way  upon  its  anterior  surface.  This  end 
of  the  kidney  reaches,  on  the  left  side,  to  about  the  upper  border  of  the 
eleventh  rib,  and  on  the  right  half  a rib’s  breadth  lower.  It  is  more- 
over directed  slightly  inwards,  so  that  the  upper  ends  of  the  two 
kidneys  are  nearer  to  each  other  than  the  lower  ends,  which  are 
smaller  and  somewhat  flattened,  diverge  slightly  from  the  spine,  and 
reach  nearly  as  low  as  the  crest  of  the  ilium.  It  may  here  be  remarked 
that,  by  placing  the  larger  end  of  a kidney  upwards  and  its  flatter 
surface  backwards,  or  by  noticing  the  relation  of  the  parts  in  the 
hilus,  it  may  be  determined  to  which  side  of  the  body  the  organ 
belongs. 

Varieties. — The  kidneys  present  varieties  in  form,  position,  absolute  and  relative 
size,  and  number.  Thus,  they  are  sometimes  found  longer  and  narrovrer,  and 
sometimes  shorter  and  more  rounded  than  usual.  Occasionally  one  kidney  is 
very  small,  whilst  the  other  is  proportionately  enlarged.  In  either  of  these  con- 
ditions the  position  of  the  kidney,  especially  as  regards  its  height  upon  the  ribs, 
must  also  vary.  Independently  of  any  other  change,  the  kidneys  may,  one  or 
both,  be  situated  low  down,  even  in  the  pelvis. 

Cases  are  now  and  then  met  with  in  which  but  one  kidney  is  present,  the 
single  organ  being  sometimes,  though  not  always,  formed  by  the  apparent  junc- 
tion of  the  two  kidneys  across  the  front  of  the  great  blood-vessels  and  vertebral 
column.  The  transverse  connecting  portion  usually  has  its  upper  border  concave, 
so  as  to  give  the  organ  a form  which  has  suggested  the  appellation  of  the  horse- 
shoe kidney.  Sometimes  two  united  kidneys  are  situated  on  one  or  other  side  of 
the  vertebral  column,  in  the  lumbar  region,  or,  but  much  more  rarely,  in  the 
cavity  of  the  pelvis.  In  other  very  rare  cases,  three  distinct  glandular  masses 
have  been  found,  the  supernumerary  organ  being  placed  either  in  front  or  on  one 
side  of  the  vertebral  column,  or  in  the  pelvic  cavity. 

Structure. — Beneath  the  layer  of  fatty  tissue  (tunica  adiposa)  which 


508 


STRUCTURE  OF  THE  KIDNEYS. 


in  the  adult  usually  surrounds  the  kidney,  but  is  accumulated  especially 
upon  its  outer  and  inner  borders,  is  the  proper  fibrous  coat  of  the  organ. 
This  coat  forms  a thin,  smooth,  but  firm  investment,  immediately  and 
closely  covering  the  whole  kidney.  It  consists  of  dense  fibro-cellular 
tissue,  and  can  be  easily  torn  oflT  from  the  substance  of  the  gland,  to 
which  it  adheres  by  minute  processes  and  vessels. 

On  splitting  open  the  kidney  by  a longitudinal  section,  from  its  outer 
to  its  inner  border  (see  fig.  475),  the  fissure  named  the  hilus  {h,  h),  is 

found  to  extend  some  distance  into  the 
interior  of  the  organ,  forming  a cavity 
within  the  solid  substance  of  the  gland 
called  thes/ttMsof  the  kidney  (s).  The 
fibrous  coat  of  the  kidney,  passing  in 
by  the  hilus,  lines  the  sides  of  the 
sinus,  and  having  reached  the  bottom 
of  that  cavity,  surrounds  the  blood- 
vessels, giving  them  sheaths  which 
accompan)'  their  principal  branches 
in  the  substance  of  the  gland,  and  is 
reflected  upon  the  divisions  of  the 
ureter  or  excretory  duct  (c,  c,  c),  to 
be  afterwards  described.  The  solid 
part  of  the  kidney,  as  is  seen  on  a 
section,  consists  of  two  substances, 
differing  from  one  another  in  aspect, 
and  usually  named,  from  their  relative 
position,  the  cortical  and  medullary 
substances.  The  external  or  cortical 
substance  (a,  a,  a,)  is  situated  imme- 
diately beneath  the  fibrous  capsule, 
and  forms  the  superficial  part  of  the 
organ  throughout  its  whole  extent  and 
to  the  depth  of  about  two  lines.  The 
cortical  substance  moreover  sends  pre- 


plan of  a longitudinal  section  of  the  kid- 
ney and  upper  part  of  the  ureter,  through 
the  hilus,  copied  from  an  enlarged  model. 
— a,  a,  a.  The  cortical  substance,  h,  b. 
Broad  part  of  two  of  the  pyramids  of 
Malpighi,  e,  e.  Section  of  the  narrow 
partor  apex  of  twoof  these  pyramids,  lying 
within  the  divisions  of  the  ureter  marked 
c,  c.  d,  d.  Summits  of  the  pyramids, 
called  papillae,  projecting  into  and  sur- 
rounded by  the  divisions  of  the  ureter, 
c,  c.  Divisions  of  the  ureter,  called  the 
calices  or  infundibula,  laid  open.  d.  A 
calix  or  infundibulum  unopened,  p.  En- 
larged upper  end  of  ureter,  named  the 
pelvis  of  the  kidney,  s.  Central  cavity  or 
sinus  of  the  kidney. 


longations  inwards  towards  the  sinus 


(septula  renum),  between  whicli  the 
medullary  substance  is  found.  The 
internal  or  medullary  substance,  on 
the  other  hand,  does  not  form  a con- 
tinuous structure,  but  is  collected  into  a series  of  conical  masses  called 
the  -pyramids  of  Malpighi  {h,  h),  the  bases  of  which  are  directed 
towards  the  surface  of  the  kidney,  while  their  apices  (e,  e,  e),  are 
turned  towards  the  sinus.  There  are  generally  more  than  twelve 
pyramids,  but  their  number  is  not  constant,  varying  from  eight  to 
eighteen.  The  greater  part  of  each  pyramid  is  embedded  in  the  cor- 
tical substance,  but  the  summits  of  these  masses,  which  project  into  the 
sinus,  are  free,  and  are  named  the  papillaefox  mamillce)  of  the  kidney 
{d,  d).  The  cortical  portion  forms  about  three-fourths,  and  the  me- 
dullary the  remaining  fourth  of  the  substance  of  the  gland. 

The  cortical  substance  is  soft  and  easily  lacerated,  the  torn  surface 


THK  DUCTS. 


509 


presenting  a rough  irregular  aspect,  and  having  a tolerably  unifurm 
red  colour.  It  is  sometimes  said  to  be  darker  than  the  medullary 
portion,  but  this  is  not  the  fact,  for,  though  the  papillae  or  summits  of 
the  pyramids  are  often  lighter,  their  bases  are  usually  darker  than  the 
surrounding  cortical  substance.  On  closely  examining  a section  of  a 
recent  kidney,  either  with  or  without  the  aid  of  a lens,  a number  of 
small  round  dark  red  points  are  seen  lying  in  the  cortical  substance  only, 
but  nowhere  reaching  quite  to  the  surface  of  the  gland.  These  are 
the  Malpighian  bodies  or  corpuscles  of  the  kidney,  to  which  we  shall 
presently  have  again  to  refer.  The  medullary  portion  of  the  kidney, 
which,  as  already  said,  forms  the  pyramids,  is  more  dense  than  the 
cortical,  and  is  distinctly  striated,  owing  to  its  consisting  of  minute 
diverging  tubes : hence  it  is  often  named  the  tubular  substance,  but 
the  cortical  substance  is  also  tubular. 

The  pyramidal  masses  found  in  the  adult  kidney  indicate  the  origi- 
nal separation  of  this  gland  into  lobules  in  the  earlier  stages  of  its 
growth.  Each  of  these  primitive  lobules  is  in  fact  a pyramid,  sur- 
rounded by  a proper  investment  of  cortical  substance,  and  is  analogous 
to  one  of  the  lobules  of  the  divided  kidneys,  seen  in  many  of  the  lower 
animals.  As  the  human  kidney  continues  to  be  developed,  the  adja- 
cent surfaces  of  the  lobules  coalesce  and  the  gland  becomes  a single 
mass,  and  the  contiguous  parts  of  the  originally  separate  cortical 
investments,  being  blended  together,  fprm  the  partitions  between  the 
pyramids  already  described.  Moreover,  upon  the  surface  of  the  kid- 
ney even  in  the  adult,  after  the  removal  of  the  fibrous  capsule,  faintly 
marked  furrows  may  be  traced  on  the  cortical  substance,  opposite  the 
intervals  between  the  bases  of  the  pyramids,  which  also  indicate  the 
position  and  course  of  large  veins. 

The  entire  substance  of  the  kidney,  whether  cortical  or  medullary, 
is  composed  of  the  uriniferous  or  excretory  ducts,  the  blood-vessels, 
lymphatics,  and  nerves,  connected  in  some  parts  by  a fine  cellular 
tissue,  which,  however,  exists  but  in  very  small  quantity,  together  with 
an  intermediate  substance,  also  very  scanty,  which  has  been  described 
as  a proper  parenchyma. 

The  ducts. — The  ureter,  or  excretory  duct  of  the  gland  {u),  is 
dilated  at  its  upper  end  as  it  approaches  the  hilus,  into  a funnel-shaped 
cavity,  compressed  before  and  behind,  named  the  fehis  of  the  kid- 
ney {p).  On  entering  the  sinus,  partly  concealed  by  the  vessels,  the 
pelvis  divides  usually  into  three,  or  sometimes  tw’o,  principal  tubes, 
which  again  subdivide  into  several  smaller  tubes  named  the  calices  or 
ivfundibula  (c,  c,  c).  These  calices,  which  vary  in  number  from 
seven  to  thirteen,  embrace  the  prominent  portions  of  the  pyramids, 
forming  short  funnel-shaped  tubes,  into  which  the  papillae  {d,  d,)  pro- 
ject. Often  a single  calix  surrounds  two,  sometimes  even  three 
papillae,  which  are  in  that  case  united  together;  hence,  too,  the  calices 
are  in  general  not  so  numerous  as  the  pyramids  and  papillae. 

Like  the  rest  of  the  ureter,  the  calices  consist  of  two  coats,  viz.,  a 
strong  external  fibro-cellular  tunic,  which  becomes  continuous  around 
the  bases  of  the  papillae  with  that  part  of  the  proper  coat  of  the  kidne}'- 
which  is  continued  into  the  sinus;  and,  secondly,  a thin  internal 

43* 


510 


THE  URINIFEROUS  TUBES. 


mucous  coat,  which  is  reflected  over  the  summit  of  each  papilla,  and 
is  moreover  prolonged  into  a multitude  of  minute  orifices  opening  on 
the  surface  of  the  papilla,  and  from  which,  on  pressing  the  gland, 
urine  may  be  made  to  exude.  These  small  orifices  vary  in  diameter 
from  T^sth  to  asoth  of  an  inch  ; they  are  frequently  collected  in  large 
numbers  at  the  bottom  of  a slight  depression  ov  fvveola  found  near  the 
summit  of  the  papilla. 

Tubuli.  uriniferi. — On  tracing  the  minute  openings  just  mentioned, 
into  the  substance  of  the  pyramids,  they  are  discovered  to  be  the 
mouths  of  small  tubes  or  ducts,  called  the  uriniferous  tubes  (tubuli  uri- 
niferi), which  thus  open  upon  the  surface  of  the  several  papillse  into 
the  interior  of  the  calices. 

As  these  tubuli  pass  up  into  the  pyramidal  substance,  they  bifurcate 
again  and  again  at  very  acute  angles,  their  successive  branches 
running  close  together  in  straight  and  but  slightly  diverging  lines,  and 
continuing  thus  to  divide  and  subdivide  until  they  reach  the  sides  and 
bases  of  the  pyramids,  from  whence  they  pass,  greatly  augmented  in 
number,  into  the  cortical  substance.  Here,  however,  they  undergo  a 
complete  change  in  their  direction,  for  whereas,  in  the  pyramids  the 
radiating  tubes  are  quite  straight,  they  in  the  cortical  part  become  at 
once  convoluted  in  a most  intricate  manner,  and  retain  this  character 
through  the  remainder  of  their  course.  The  straight  portions  of  these 
tubuli  were  early  recognised,  and  are  sometimes  named  the  ducts  of 
Bellini,  but  the  existence  of  tubes  in  the  eortical  substance  was  for  a 
long  time  unknow’n;  in  this  situation  the  tortuous  uriniferous  ducts  are 
called  the  tubes  of  Ferrein.  Within  the  pyramids,  towards  their  base, 
the  straight  tubes  are  described  as  being  collected  into  fasciculi,  the 
tortuous  tubuli  given  off  from  which  into  the  cortical  substance  form 
little  indistinct  conical  masses,  reaching  to  the  surface  of  the  kidney, 
which  presents  in  consequence  a minutely  lobulated  or  granular  aspect. 
These  aggregations  of  the  uriniferous  tubes  in  separate  fasciculi  and 
masses,  appear  connected  in  some  degree  with  the  arrangement  of  the 
intermediate  blood-vessels,  especially  of  the  veins.  They  have  been 
named  the  'pyramids  of  Ferrein,  a great  number  of  which  are  included 
in  each  of  the  pyramids  of  Malpighi  and  its  corresponding  cortical 
substance. 

On  a section  made  across  the  base  of  a papilla,  Krause  has  counted 
the  openings  of  about  one  hundred  of  the  straight  tubes  in  a square 
line;  and  Huschke  has  enumerated  from  four  to  five  hundred  larger 
ones  with  as  many  of  smaller  size  on  the  entire  section  of  the  base  of 
a single  papilla.  The  uriniferous  tubes  are  largest  near  their  orifices, 
at  a short  distance  from  which,  within  the  papillae,  their  diameter 
varies,  according  to  Huschke,  from  4-J^th  to  of  an  inch.  Further 
on  in  the  pyramid  they  become  smaller,  measuring  about  g-^^th  of  an 
inch  in  diameter,  and  then  do  not  diminish  as  they  continue  to  bifur- 
cate, but  remain  nearly  of  the  same  uniform  average  diameter,  until 
they  enter  the  cortical  substance,  where  the  convoluted  tubuli  vary 
considerably  in  diameter,  and  many  of  them,  indeed,  (at  least  when 
injected,)  present  great  inequalities  at  intervals  along  their  course,  but 


BLOOD-VESSELS  OF  THE  KIDNEYS. 


511 


they  maintain  commonly  the  same  average  width  as  the  straight  tubes, 
namely  gcj^th  of  an  inch. 

The  uriniferous  tubes  form  a system  of  canals  apart  from  the  blood- 
vessels, which  latter  are  ramified  on  their  walls  in  form  of  a fine 
capillary  network,  and  at  certain  parts  have  a more  curious  relation 
to  them,  to  be  presently  described.  The  convolution  of  the  tubes  pro- 
vides for  a large  extent  of  secreting  surface  in  a small  space.  Their 
parietes  are  formed  of  a transparent  and  homogeneous  basement 
membrane,  or  membrana  propria,  lined  by  a spheroidal  epithelium, 
W’hich  usually  occupies  about  two-thirds  of  the  diameter  of  the  tube. 
(Fig.  476,  A,  B,  c.) 

Diflerent  statements  are  made  by  different  observers  as  to  the  mode 
in  which  the  convoluted  uriniferous  tubes  terminate  or  (tracing  them 
in  the  reverse  direction)  commence  in  the  cortical  substance.  Accord- 
ing to  the  description  given  by  Mr.  Bowman,  each  tubulus  begins  by 
a little  saccular  dilatation,  which  embraces  one  of  the  vascular  tufts 
named  the  Malpighian  bodies, — the  uriniferous  tubes,  in  fact,  being 
continued  from,  or  rather  forming  by  their  dilated  commencement,  the 
capsules  by  which,  as  noticed  by  previous  observers,  these  bodies  are 
surrounded.  The  tortuous  tubuli  have  also  been  seen  forming  loops, 
either  by  the  junction  of  adjacent  tubes,  or,  as  stated  by  Mr.  Toynbee,* 
by  the  reunion  of  two  branches  proceeding  from  the  same  tube  ; in 
either  case,  new  branches  may  arise  from  such  loops.  Other  anato- 
mists again  hold,  that  the  tubuli  also  arise  by  free  and  simply  closed 
extremities. 

Blood-vessels. — The  kidneys  are  highly  vascular,  and  derive  their 
blood  from  the  right  and  left  renal  arteries  (vol.  i.  p.  602),  which  are 
very  large  in  proportion  to  the  size  of  the  organs  they  supply.  Each 
renal  artery  divides  into  four  or  five  branches,  which,  passing  in  at 
the  hilus,  between  the  vein  and  ureter,  may  be  traced  into  the  sinus  of 
the  kidney,  where  they  lie  amongst  the  infundibula,  together  with 
which  they  are  usually  embedded  in  a quantity  of  fat.  Penetrating 
the  substance  of  the  organ  between  the  papillae,  the  arterial  branches 
enter  the  cortical  substance  found  in  the  intervals  between  the  medul- 
lary cones,  and  go  on,  accompanied  by  a sheathing  of  cellular  tissue 
derived  from  the  proper  coat  and  dividing  and  subdividing,  to  reach 
the  bases  of  the  pyramids,  where  they  form  numerous  anastomotic 
arches.  From  these  arches  a multitude  of  branches  are  given  oflf, 
and,  after  ramifying  through  the  cortical  substance,  at  length  end  in  a 
system  of  capillary  vessels,  which  exist  through  the  whole  substance 
of  the  kidney,  and  form  a network  upon  the  uriniferous  tubes.  In  the 
medullary  portion  of  the  kidney,  where  the  uriniferous  tubes  are 
straight,  the  blood-vessels  form  oblong  meshes  parallel  with  the  tubuli. 
In  the  cortical  substance,  the  distribution  of  the  small  arteries  is  pecu- 
liar, for,  before  terminating  in  the  common  capillary  system,  they, 
with  probably  very  few  exceptions,  enter  into  the  Malpighian  bodies, 
or  glomeruli.  All  the  capillaries  of  the  kidney  end  in  venous  radicles, 
which  unite  to  form  the  renal  vein. 


* Medico-Chir.  Transactions.  1846. 


512 


THE  MALPIGHIAN  CORPUSCLES. 


The  Malpighian  corpuscles. — These  small  red  bodies,  or  glomeruli, 
discovered  by  Malpighi  (who,  however,  did  not  know  their  intimate 
structure),  lie  embedded  in  the  cortical  substance,  surrounded  loosely 
by  little  capsules.  They  are  rounded  or  slightly  oblong  in  shape,  and 
have  an  ordinary  diameter  of  Tfiyth  of  an  inch,  but  sometimes  only 
of  2^oth  or  2To*h  of  an  inch.  When  oblong,  Krause,  has  found  them 
to  measure  of  an  inch  in  length,  and  TT0lh  in  width. 

These  glomeruli  were  described  by  Ruysch  as  consisting  of  a little 
coiled  artery.  They  are  really,  however,  little  vascular  tufts  formed. 


Fig.  476. 


Fig.  477. 


Fig.  476.  Portions  of  the  uriniferous  lubes,  magnified  (Baly).  a.  Portion  from  the  cortical 
Bubsiance,  lined  by  its  epithelium.  B.  Epithelial  cells,  more  highly  magnified  (about  700  times), 
c.  Portion  of  tube  from  the  medullary  subsl.ince,  at  one  part  deprived  of  its  epithelial  lining. 

Fig.  477.  Plan  of  the  renal  circulation;  copied  from  Mr.  Bowman’s  paper,  a.  A branch  of 
the  renal  artery  giving  off  several  Malpighian  twigs.  1.  An  afferent  twig  to  the  capillary  tuft 
contained  in  the  Malpighian  body,  m ; from  the  Malpighian  body  the  uriniferous  tube  is  seen 
taking  its  tortuous  course  to  f.  2,2.  Efferent  veins ; that  which  proceeds  from  the  Malpighian 
body  is  seen  to  be  smaller  than  the  corresponding  artery.  p,p.  The  capillary  venous  plexus, 
ramifying  upon  the  uriniferous  lube.  This  plexus  receives  its  blood  from  the  efferent  veins,  2,  2, 
and  transmits  it  to  the  branch  of  the  renal  vein,  v. 


not,  as  Ruysch  supposed,  by  the  convolutions  of  a single  vessel,  but 
by  those  of  two  vessels,  one  afferent  (fig.  477,’)  the  other  efferent  (®), 
which  enter  and  pass  out  of  the  glomerulus  (m)  close  to  one  another. 
The  afferent  vessel  immediately  divides  into  several  branches,  which 
cover  the  surface  of  the  glomerulus,  and  end  in  a finer  set  of  central 
vessels.  From  these  the  efferent  vessel  arises,  and,  passing  out  of  the 
tuft,  at  length  divides  into  capillaries,  which  form  a plexus  around  the 
adjacent  tubuli.  Mr.  Bowman  regards  the  efferent  vessel  as  a vein, 
and  consequently  as  having  an  arrangement  comparable  to  that  of  the 
portal  vein,  and  supports  his  view  by  a reference  to  the  peculiar  dis- 
position of  the  vessels  in  the  kidneys  of  reptiles.  Others  look  on  a 
Malpighian  tuft  as  merely  an  example  of  an  artery  breaking  up  into  a 
rete  mirabile,  and  then  after  being  reconstructed,  continuing  beyond 
as  the  efferent  vessel.  All  the  small  arteries  of  the  kidney,  it  must  be 
borne  in  mind,  do  not  form  glomeruli  before  ending  in  the  capillary 


VEINS  OF  THE  KIDNEY. 


513 


network  of  the  gland,  for  some  of  thena  divide  at  once  into  capillaries, 
without  entering  these  tufts. 

Relation  of  the  Malpighian  bodies  to  the  uriniferous  tubes. — It  was 
thought,  by  Ruysch,  that  the  single  convoluted  blood-vessel,  supposed 
by  him  to  form  the  glomerulus,  ultimately  became  continued  on  as  a 
straight  uriniferous  tube ; but  subsequent  researches  have  shown  that, 
though  the  Malpighian  bodies  have  peculiar  relations  with  the  com- 
mencing tubuli,  there  is  no  continuity  between  the  channels  of  the 
blood-vessels  and  those  of  the  secretina:  ducts.  The  true  relation  of 
the  two  was  discovered  by  Mr.  Bowman,  and  is  essentially  this, 
that  the  uriniferous  tube  (t),  by  becoming  enlarged,  forms  a capsule 
into  which  one  of  the  vascular  tufts  {m)  projects,  so  as  to  be  entirely 
enclosed  within  it ; and  that  the  two  vessels,  afferent  (^)  and  efferent 
(^),  which  form  the  tuft,  pierce  this  capsule  usually  close  to  each 
other.  Mr.  Bowman  inferred  from  his  observations  that  the  dilatation 
was  placed  at  the  end  or  rather  commencement  of  a tube,  but  it  has 
since  been  found  by  Gerlach  and  others,  that  it  may  be  formed  on  one 
side.  Hence  it  would  appear  that  the  capsules  in  question  may  be 
either  lateral  or  terminal;  and  for  aught  that  has  yet  been  proved  to 
the  contrary,  lateral  capsules  may  exist  both  on  tubes  which  issue 
from  terminal  ones,  and  on  tubes  which  at  their  commencement  are 
joined  with  others  or  form  loops. 

According  to  Bowman,  the  epithelium  becomes  remarkably  thin 
within  the  capsule,  and,  in  the  frog,  is  covered  with  cilia  at  the  neck 
of  the  dilated  portion.  By  the  same  observer,  it  is  further  stated,  that 
neither  the  epithelium  nor  the  basement  membrane  of  the  capsule  is 
reflected  over  the  glomerulus,  the  vessels  of  which  therefore  lie,  as  it 
were,  naked  in  the  capsular  cavity.  Gerlach,  on  the  other  hand, 
describes  the  tuft  of  vessels  as  covered  with  a thick  layer  of  nucleated 
cells,  continued  from  a similar  layer  lining  the  capsule.* 

Veins. — Small  veins,  arising  by  numerous  venous  radicles  from' the 
capillary  network  of  the  kidney,  are  seen  near  the  surface  of  the 
gland,  arranged  so  as  to  leave  between  them  minute  spaces,  which 
appear  nearly  to  correspond  with  the  bases  of  the  so-called  pyramids 
of  Ferrein.  These  vessels,  which  sometimes  have  a stellate  arrange- 
ment {stellulcB,  Verheyen,)  end  in  larger  veins,  which  again  unite  into 
arches  around  the  bases  of  the  pyramids  of  Malpighi.  From  thence 
venous  trunks  proceed,  in  company  with  the  arteries,  through  the 
cortical  envelope  between  the  pyramids,  to  the  sinus  of  the  kidney. 
Joining  together,  they  escape  from  the  hilus,  and  ultimately  form  a 
single  vein,  which  lies  in  front  of  the  artery,  and  ends  in  the  inferior 
vena  cava. 

A number  of  vessels,  both  veins  and  arteries,  enter  the  proper  coat 

* Mr.  Toynbee,  whose  views  are  different  from  those  above  given , conceives  that  the 
capsule  is  not  a dilated  portion  of  a uriniferous  tube,  but  is  an  independent  investment,  con- 
tinuous  neither  with  the  tube  nor  with  the  blood-vessels,  but  expanded  over  and  enveloping 
the  terminations  of  both.  Further,  he  believes  that  the  blood-vessels  passing  into  and  out 
of  the  tuft  perforate  one  end  of  this  proper  capsule,  whilst  the  uriniferous  tube  enters  at  the 
opposite  point,  becomes  twisted  into  a coil  in  contact  with  the  convoluted  blood-vessels,  and 
then  again  emerges  from  the  capsule. 


514 


THE  SUPRA  RENAL  CAPSULES. 


of  tlie  kidney  from  the  cortical  substance,  and  some  supply  also  the 
surrounding  cellular  or  adipose  tissue. 

Absorbents. — The  lymphatics  of  the  kidney  are  numerous,  consisting 
of  a superficial  set,  and  of  deep  lymphatics  which  issue  from  the  hilus 
with  the  blood-vessels. 

Nerves. — The  nerves  which  have  been  traced  into  these  organs  are 
small.  They  come  immediately  from  the  renal  plexus  and  the  lesser 
splanchnic  nerve,  and  contain  filaments  derived  from  both  the  sympa- 
thetic and  cerebro-spinal  systems. 

Intermediate  substance. — Bowman  has  pointed  out  the  existence  of 
a firm  granular  substance,  lying  betw'een  and  uniting  the  tubes,  as 
w'ell  as  the  vessels,  in  the  medullary  part  of  the  kidney;  he  compares 
it  to  a blastema,  and  states  that  it  is  probably  composed  of  ceils. 
Under  the  name  of  the  proper  parenchyma  of  the  kidney,  Mr.  Toynbee 
has  also  described  a substance,  composed  of  cells,  as  interposed 
between  and  surrounding  the  tubuli,  in  the  cortical  part  as  well  as 
elsew'here.  He  further  states,  that  the  fine  filaments  of  the  nerves 
within  the  kidney  have  appeared  to  him  to  be  connected  with  the 
intertubular  or  parenchymal  cells.* 

Development. — The  development  of  the  kidneys,  and  also  that  of  the  supra-renal 
capsules  next  to  be  described,  will  be  given  with  that  of  the  genito-urinary  organs 
generally. 

The  Urine. — This  is  a highly  complex  fluid,  containing  in  solution  animal  com- 
pounds characterized  by  having  a large  amount  of  nitrogen  in  their  composition, 
and  derived,  it  would  seem,  from  the  waste  of  the  tissues;  saline  substances,  and 
adventitious  matters  which  have  been  introduced  into  the  blood.  The  average 
quantity  secreted  daily  is  about  30  fluid  ounces.  Its  specific  gravity  varies  in 
health  from  1-015  to  1-030,  but  1-020  is  the  average  standard.  It  is  acid  in  its 
reaction,  and  contains  some  mucus  and  epithelium.  One  thousand  parts  of  ordi- 
nary urine  contain  933  pts.  of  water,  and  67  of  solid  matter.  Of  the  latter,  30  pts. 
con.sist  of  urea,  the  characteristic  nitrogenous  ingredient  of  urine;  17  pts.  consist 
of  extract  with  salts  soluble  in  alcohol;  15  pts.  are  fixed  salts,  and  1 pt.  is  uric 
acid. 

SUPRA-RENAL  CAPSULES. 

The  supra-renal  capsules,  or  supra-renal  glands  (glandulas  supra- 
renales;  capsulse  supra-renales,  seu  atrabilari®;  renes  succenluriati), 
are  two  gland-like  bodies,  situated  one  on  each  side  of  the  vertebral 
column,  and,  as  their  name  implies,  above  the  kidneys.  Each  of  them 
is  a flattened,  triangular  body,  somewhat  resembling  a cocked  hat  in 
shape,  which  surmounts  the  corresponding  kidney.  Its  upper  border, 
convex  and  thin,  is  directed  inwards  and  upwards.  Its  base  or  con- 
cave border,  which  rests  upon  the  anterior  and  inner  part  of  the 

* Mr.  Goodsir  (Lond.  and  Edin.  Journ.  of  Med.  Science,  May,  1842),  and  more  lately 
Dr.  Jolinson  (Cyclop,  of  Anat.  vol.  iv.  p.  239)  have  described  a fibro-cellular  framework  or 
matrix  as  pervading  every  part  of  the  renal  substance,  and  supporting  the  uriniferous  tubes 
and  blood-vessels.  We  must  confess,  that  although  small  bundles  of  fibrous  or  cellular 
tissue  are  met  with  here  and  there  accompanying  vessels  in  the  substance  of  the  kidney, 
we  have  not  been  able  to  observe  any  continuous  pervading  structure  of  fibro-cellular  tissue. 
The  apparently  reticular  framework  which  is  displayed  by  washing  a thin  slice  of  the 
kidney  lias  seemed  to  us  to  be  formed  by  the  basement membrane  of  the  transversely  or 
obliquely  cut  tubes,  deprived  of  epithelium  and  connected  by  a transparent  tissue,  which  is 
doubtless  made  up  principally  of  vessels  (although  in  the  uninjected  state,  these  do  not 
definitely  appear)  and  has  granular  corpuscles  irregularly  dispersed  in  it. 


SUPRA-RENAL  CAPSULES. 


515 


summit  of  the  kidney,  to  which  it  is  connected  by  loose  cellular  tissue, 
is  thick,  and  almost  always  deeply  grooved.  The  posterior  surface 
rests  upon  the  diaphragm.  Its  anterior  surface  is  covered  on  the 
right  side  by  the  liver,  and  on  the  left  by  the  pancreas  and  spleen. 
The  inner  border  of  the  right  supra-renal  capsule  is  in  contact  with 
the  vena  cava  inferior,  and  that  of  the  left  with  the  aorta.  The 
right  capsule,  like  the  right  kidney,  is  placed  lower  down  than 
the  left. 

The  supra-renal  capsules  vary  in  size  in  different  individuals,  and 
the  left  is  usually  somewhat  narrower  at  its  base,  but  is  longer  from 
above  downwards,  and  usually  larger  than  the  right.  They  measure 
from  an  inch  and  a quarter  to  an  inch  and  three  quarters  in  height, 
and  about  an  inch  and  a quarter  in  width  ; their  thickness  is  from  two 
to  three  lines.  The  weight  of  each  supra-renal  capsule  in  the  adult  is 
from  one  to  two  drachms. 

Besides  cellular  tissue  mixed  frequently  with  much  fat,  the  supra- 
renal capsules  have  a thin  fibrous  investment,  which  also  sends  nume- 
rous processes  into  their  interior,  accompanied  by  many  blood-vessels. 
These  processes  enter  certain  furrows,  varying  in  depth  and  extent, 
by  which  the  surface  of  the  organ  is  marked,  especially  in  front  and 
upon  its  base.  Externally,  the  supra-renal  capsules  have  a yellowish 
or  brownish-yellow  colour;  but,  when  divided,  they  seem  to  consist  of 
two  substances,  viz.,  one  external  or  cortical,  which  is  of  a deep  yellow 
colour,  firm  and  striated,  and  forms  the  principal  mass  of  the  organ  ; 
the  other  internal,  which  is  dark,  soft,  pulpy,  and  of  a brownish-black 
hue.  Many  anatomists  describe  a cavity  within  this  soft  central  sub- 
stance, but  some  attribute  the  seeming  cavity  to  accidental  laceration 
of  the  soft  substance,  while  others  look  upon  it  as  a venous  sinus. 
The  name  of  atrabiliary  capsules,  given  to  these  organs,  has  reference 
to  the  dark,  black  colour  of  their  interior. 

The  cortical  striated  part  of  the  supra-renal  capsules  has  been  found, 
by  Mr.  Simon,  to  consist  of  distinct  closed  tubes,  arranged  in  columnar 
masses,  perpendicularly  to  the  surface  of  the  organ.  These  tubes 
measure,  on  an  average,  about  y^gth  of  an  inch  in  diameter.  They 
have  no  communication  with  one  another,  but  each  consists  of  a very 
delicate  constituent  membrane,  which  is  complete  on  all  sides.  The 
small  blood-vessels  run  parallel  to  these  tubes,  frequently  anastomose 
together  between  them,  and  suri'ound  each  tube  with  a fine  capillary 
network.  In  the  interior  of  the  tubes,  are  found  nucleus-like  bodies, 
mixed  with  minute  yellowish  granules,  and  oily  particles  with  granular 
matter  adhering  to  them,  also  nucleated  cells  containing  granular 
matter  and  oily  molecules.  According  to  Mr.  Gulliver’s  observations, 
the  nucleated  corpuscles  or  cells  always  exist,  in  large  numbers,  in 
the  supra-renal  bodies  of  ruminant  animals,  but  they  occur  more 
sparingly  in  the  human  subject,  and  in  other  animals.  They  resemble 
the  lymph  globules  in  size,  but  are  often  of  a reddish  colour.  The 
granules,  or  minute  spherules  (Gulliver)  form,  however,  the  chief 
constituents  of  the  substance  of  the  supra-renal  gland.  Their  size 
is  very  unequal,  varying  from  gono^h  to  of  an  inch,  and 

averaging  about  Touo^th  of  an  inch.  Their  great  peculiarity  consists 


616 


THK  URETERS. 


in  iheir  undergoing  no  change  when  treated  by  chemical  reagents, 
(acids,  alkalies,  and  salts,)  excepting  after  the  lapse  of  a considerable 
time.  The  dark  pulpy  pori/ore  contained  in  the  of  the  supra- 

renal body  seems  to  be  principally  composed  of  a plexus  of  minute 
ramified  veins,  surrounded  by  the  peculiar  substance  of  the  organ, 
and  having  sometimes  amidst  them  a central  venous  sinus.  Mr.  Gul- 
liver has  frequently  found  in  the  blood  of  the  supra-renal  veins  numerous 
minute  spherules,  which  could  not  be  distinguished  from  those  of  the 
glands. 

No  excretory  duct  has  been  found  connected  with  these  organs,  the 
office  of  which  is  entirely  unknown. 

Vessels. — The  supra-renal  bodies  receive  arteries  from  three  sources, 
viz.,  from  the  aorta,  the  phrenic,  and  the  renal  arteries.  The  distribu- 
tion of  their  capillary  vessels  has  already  been  mentioned. 

The  veins,  which  pass  out  from  the  centre,  are  usually  united  into 
one  for  each  organ.  The  right  vein  enters  the  vena  cava  inferior 
immediately,  whilst  the  left,  after  a longer  course,  terminates  in  the 
left  renal  vein. 

The  lymphatics  are  but  little  known. 

Nerves. — The  nerves  are  exceedingly  numerous.  They  are  derived 
from  the  solar  plexus  of  the  sympathetic,  and  from  the  renal  plexuses. 
According  to  Bergmann,  some  filaments  come  from  the  phrenic  and 
pneumogastric  nerves. 

THE  URETERS. 

The  ureters  are  two  nearly  cylindrical  tubes,  one  right,  the  other 
left,  which  conduct  the  urine  from  the  kidneys  into  the  bladder.  The 
upper,  dilated,  funnel-shaped  end  of  these  excretory  ducts,  called  the 
pelvis  of  the  kidney,  together  with  its  branches  and  their  ultimate  divi- 
sions, named  the  calices,  have  already  been  described  (p.  509).  To- 
wards the  lower  part  of  the  hilus  of  the  kidney,  the  so-called  pelvis 
becomes  gradually  contracted,  and,  opposite  the  lower  end  of  the 
gland,  assumes  the  name  of  ureter,  which  extends  downwards  from 
thence  to  the  posterior  and  under  part  or  base  of  the  bladder,  into 
which  viscus  the  ureters  of  both  sides  open,  after  passing  obliquely 
through  its  coats. 

The  ureters  measure  from  sixteen  to  eighteen  inches  in  length,  and 
their  ordinary  width  is  about  that  of  a large  quill.  They  are  frequently, 
however,  dilated  at  intervals,  especially  near  their  lower  end.  The 
narrowest  part  of  the  tube,  excepting  its  orifice,  is  that  contained  in 
the  walls  of  the  bladder. 

(,  Each  ureter  (fig.  478,  u,)  passes,  at  first,  obliquely  downwards  and 
inwards,  to  enter  the  cavity  of  the  true  pelvis,  and  then  curves  down- 
wards, forwards,  and  inwards,  to  reach  the  side  and  base  of  the 
bladder  (a).  In  its  whole  course,  it  lies  close  behind  or  beneath  the 
peritoneum  (r),  and  is  connected  to  neighbouring  parts  by  loose 
cellular  tissue.  Superiorly,  it  rests  upon  the  psoas  muscle,  and  is 
crossed,  very  obliquely,  below  the  middle  of  the  psoas,  by  the  sper- 
matic vessels,  which  descend  in  front  of  it.  The  right  ureter  is  close 
to  the  inferior  vena  cava.  Lower  down,  the  ureter  passes  over  the 


THE  BLADDER. 


517 


common  iliac,  or  the  external  iliac  vessels,  behind  the  termination  of 
the  ileum  on  the  right  side  and  the  sigmoid  flexure  of  the  colon  on  the 
left.  Descending  into  the  pelvis,  and,  entering  the  fold  of  peritoneum, 
forming  the  corresponding  posterior  false  ligament  of  the  bladder,  it 
gains  the  lateral  part  of  the  base  of  that  viscus,  upon  which  it  runs 
downwards  and  forwards,  below  the  obliterated  hypogastric  artery, 
and  crossed  upon  its  inner  side,  in  the  male,  by  the  vas  deferens  (i), 
which  passes  down  between  the  ureter  and  the  bladder.  In  the  female, 
the  ureters  run  along  the  sides  of  the  cervix  uteri,  and  upper  part  of  the 
vagina  before  reaching  the  bladder,  and  hence  they  are  proportionally 
somewhat  longer  than  in  the  male. 

Having  reached  the  base  of  the  bladder  on  each  side,  about  two 
inches  apart  from  one  another,  the  ureters  (fig.  479,®)  enter  its  coats, 
and  running  obliquely  through  them  for  nearly  an  inch,  passing 
at  first  through  the  muscular  coat,  and  then  between  it  and  the  mucous 
membrane,  open  at  length  upon  the  inner  surface  by  two  narrow  and 
oblique  slit-like  openings,  w'hich  are  situated,  in  the  male,  about  an 
inch  and  a half  behind  the  prostate,  and  rather  more  than  that  distance 
from  each  other.  This  oblique  passage  of  the  ureter  through  the 
vesical  walls,  although  allowing  the  urine  to  flow  into  the  bladder,  has 
the  effect  of  preventing  its  return  up  the  ureter  towards  the  kidney. 

Structure. — The  walls  of  the  ureter  are  pinkish  or  bluish  white  in 
colour.  They  consist  externally  of  a dense,  firm,  cellular  coat,  which 
in  quadrupeds  decidedly  contracts  when  artificially  irritated,  and  pro- 
bably contains  pale  muscular  fibres.  According  to  Huschke,  it  con- 
sists of  two  layers  of  longitudinal  fibres,  with  an  intermediate  one 
composed  of  transverse  fibres.  It  becomes  continuous  above  at  the 
calices,  with  the  proper  capsule  of  the  kidney. 

Internally,  the  ureter  is  lined  by  a thin  and  smooth  mucous  mem- 
brane, which  presents  a few  longitudinal  folds  when  the  ureter  is  laid 
open.  It  is  prolonged  above  upon  the  papillte,  and  into  the  uriniferous 
tubes,  and  below  becomes  continuous  with  the  lining  membrane  of  the 
bladder.  The  epithelial  particles  are  of  the  spheroidal  or  transitional 
form. 

Vessels. — The  ureter  is  supplied  with  blood  from  small  branches  of 
the  renal,  the  spermatic,  the  internal  iliac,  and  the  inferior  vesical 
arteries.  The  veins  end  in  various  neighbouring  vessels.  The  nerves 
come  from  the  inferior  mesenteric,  spermatic,  and  hypogastric  plexuses. 

Varieties. — Sometimes  there  is  no  funnel-shaped  expansion  of  the  ureter  at  its 
upper  end  into  a pelvis,  but  the  calices  unite  into  tvro  narrow  tubes,  which  after- 
wards coalesce.  Occasionally,  the  separation  of  these  two  tubes  continues  lower 
down  than  usual,  and  even  reaches  as  low  as  the  bladder,  in  which  case  the 
ureter  is  double.  In  rare  cases,  a triple  ureter  has  been  met  with. 

THE  URINARY  BLADDER. 

The  urinary  bladder  (vesica  urinaria)  is  the  hollow  membranous 
and  muscular  viscus  which  receives  the  urine  poured  into  it  through 
the  ureters,  retains  it  for  a longer  or  shorter  period,  and  finally  expels 
it  through  the  urethra. 

During  infancy  it  is  pyriform,  and  is  found  in  the  abdomen,  but  in 
VOL.  II.  44 


518 


THE  BLADDER, 


the  adult  (fig.  478,  a,)  it  is  situated  in  the  pelvic  cavity  behind  the 
pubes  (g),  and  in  front  of  the  rectum  {b)  in  the  male;  but  separated 
Irom  that  intestine  by  the  uterus  and  vagina  in  the  female. 


Fig.  478. 


Lateral  view  of  the  viscera  of  the  male  pelvis.  (Qnain’s  Arteries,  PI.  LX.)  a.  Bladder,  b.b'. 
Rectum,  c.  Membranous  portion  of  the  urethra,  d.  Section  of  left  crus,  or  corpus  cavernosum. 
e.  Bulbous  extremity  of  corpus  spongiosum  or  bulb  of  urethra,  f.  Covvper’s  gland,  g.  Section 
of  body  of  pubes,  h.  Sphincter  ani  muscle,  i.  Part  of  left  vas  deferens,  m.  .Articular  surface 
ofs.icrum.  n.  Spine  of  left  ischium  sawn  off.  o.  Coccyx,  p.  Prostate  gland,  r,  r.  Peritoneum, 
r'.  Cul-de-sac  between  bladder  and  rectum,  u.  Left  ureter,  v.  Lett  vesicula  seminalis. 

The  size  and  shape  of  the  bladder,  its  position  in  the  abdomino-pelvic 
cavity,  and  its  relations  to  surrounding  parts,  vary  greatly,  according 
to  its  state  of  distension  or  collapse.  When  quite  empty,  the  bladder 
lies  deeply  in  the  pelvis,  appearing  as  a triangular  sac,  flattened  before 
and  behind,  having  its  base  turned  downwards  and  attached,  whilst 
its  apex  reaches  up  behind  the  symphysis  pubis.  When  slightly  dis- 
tended, it  is  still  contained  within  the  pelvic  cavity,  and  has  a rounded 
form  ; but  when  completely  filled,  it  rises  above  the  brim  of  the  pelvis, 
and  becomes  ovoidal,  or  egg-shaped,  its  larger  end,  which  is  also 
called  the  base,  or  inferior  fundus,  being  directed  downwards  and 
backwards  towards  the  rectum  in  the  male  and  the  vagina  in  the 
female;  and  its  smaller  end  or  summit,  or  superior  fundus,  poinUng 
towards  the  lower  part  of  the  anterior  wall  of  the  abdomen.  The 
long  axis  of  the  distended  bladder  is  therefore  inclined  obliquely  up- 
wards and  forwards  from  the  base  to  the  summit,  in  a line  directed 
from  the  coccyx  to  some  point  between  the  pubes  and  the  umbilicus. 
In  being  gradually  distended,  the  bladder  curves  slightly  forwards,  so 
that  it  becomes  more  convex  behind  than  in  front,  and  its  upper  end 
is  by  degrees  turned  more  and  more  towards  the  front  of  the  abdomen. 
Lastly,  the  bladder,  when  filled,  appears  slightly  compressed  from 
before  backwards,  so  that  its  diameter  in  that  direction  is  less  than 


THE  BLADDER. 


519 


from  side  to  side.  Its  longest  diameter  in  the  male  is  from  base  to 
summit,  but  in  the  female,  its  breadth  is  greater  than  its  height ; and 
its  capacity  is  said  to  be,  on  the  whole,  larger  than  in  the  former  sex. 
The  portion  of  the  bladder  situated  between  the  base  and  the  summit 
is  often  called  the  body. 

At  the  lower  part  of  the  anterior  surface  of  this  organ,  immediately 
in  front  of  the  base,  is  a narrow  funnel-shaped  portion,  named  the 
cervix,  or  neck,  which  forms  the  outlet  of  the  bladder,  and  serves  also 
to  attach  it  below  to  the  urethra.  While  freely  movable  in  all  other 
directions  upon  surrounding  parts,  the  bladder  is  still  further  fixed 
below  to  the  inside  of  the  pelvis,  by  certain  reflections  of  the  recto- 
vesical fascia,  named  the  true  ligaments  of  the  bladder.  It  is  supported, 
moreover,  by  firm  cellular  connexions  with  the  rectum  or  vagina, 
according  to  the  sex,  also  by  the  two  ureters,  the  obliterated  hypo- 
gastric arteries,  and  the  urachus,  by  numerous  blood-vessels,  and, 
lastly,  by  a partial  covering  of  the  peritoneum,  which,  as  it  is  being 
reflected  to  or  from  this  organ  in  different  directions,  forms  certain 
folds  or  duplicatures,  named  the  false  ligaments  of  the  bladder.  All 
these  parts  will  now  be  separately  described,  as  well  as  the  relations 
of  the  different  surfaces  of  the  bladder  itself,  supposed  to  be  moderately 
distended. 

The  anterior  surface  is  entirely  destitute  of  peritoneum,  and  is 
placed  behind  the  triangular  ligament  of  the  urethra,  the  sub-pubic 
ligament,  the  symphysis  and  body  of  the  pubes,  and,  if  the  organ  be 
full,  the  lower  part  of  the  anterior  wall  of  the  abdomen.  It  is  con- 
nected to  these  parts  by  loose  cellular  tissue,  and  to  the  back  of  the 
pubes  by  two  strong  bands  of  the  vesical  fascia,  named  the  anterior 
true  ligafnents.  This  surface  of  the  bladder  may  be  punctured  above 
the  pubes  without  wounding  the  peritoneum.  In  the  female,  the  front 
of  the  bladder  corresponds,  beneath  the  arch  of  the  pubes,  with  the 
part  of  the  vulva  between  the  orifice  of  the  urethra  and  the  clitoris. 

The  summit  (sometimes  named  the  superior  fundus)  is  connected 
to  the  anterior  abdominal  wall  by  a median  cord,  named  the  urachus, 
vphich  is  composed  of  fibro-cellular  tissue,  mixed  near  the  bladder 
with  some  muscular  fibres.  This  cord,  which  becomes  narrower  as 
it  ascends,  passes  upwards  fro.m  the  apex  of  the  bladder  behind  the 
linea  alba,  and  in  front  of  the  peritoneum,  to  reach  the  umbilicus, 
where  it  becomes  blended  with  the  dense  fibrous  tissue  found  in  that 
situation.  The  urachus  is  the  vestige  of  a foetal  structure,  to  which 
we  shall  have  again  to  advert.  Two  other  rounded  cords  formed  by 
the  obliterated  hypogastric  arteries,  and  found,  one  on  each  side  of  the 
urachus,  also  ascend  from  the  bladder  to  the  umbilicus.  In  front  of 
these  three  cords,  the  summit  of  the  bladder  has  no  peritoneal  covei’- 
ing,  and  when  the  viscus  is  filled,  touches  the  abdominal  parietes. 
Behind  them,  on  the  other  hand,  it  receives  a covering  from  that 
serous  membrane,  and  has  a few  convolutions  of  the  small  intestine 
resting  upon  it. 

The  posterior  surface  of  the  bladder  is  entirely  free,  and  covered 
everywhere  by  the  peritoneum  (?•),  w’hich  is  prolonged  also  for  a short 
distance  upon  the  base  of  the  bladder.  In  the  male,  this  surface  is  in 


520 


THE  BLADDER. 


contact  with  the  rectum  (b),  and  in  the  female  with  the  uterus,  some 
convolutions  of  the  small  intestine  descending  between  it  and  those 
parts,  unless  the  bladder  be  very  full.  Beneath  the  peritoneum,  on 
each  side  of  the  lower  portion  of  this  surface,  is  found  a part  of  the 
vas  deferens  (/). 

The  sides  of  the  bladder,  which,  when  it  is  distended,  are  rounded 
and  prominent,  are  each  of  them  crossed  obliquely  by  the  cord  of  the 
obliterated  hypogastric  artery,  which  springs  posteriorly  from  the 
superior  vesical  artery,  and  runs  forwards  and  upwards  towards  the 
summit  of  the  bladder.  Behind  and  above  this  cord  the  side  of  the 


bladder  is  covered  by  the  peritoneum,  but  below  and  in  front  of  it  the 
peritoneum  does  not  reach  the  bladder,  which  is  here  connected  to  the 
sides  of  the  pelvic  cavity  by  loose  cellular  tissue,  containing  fat,  and, 
near  its  anterior  and  lower  part,  by  a broad  expansion  from  the  vesi- 
cal fascia.  The  vas  deferens  (i)  crosses  over  the  lower  part  of  this 
lateral  surface,  from  before,  backwards  and  downwards,  and  turning 
over  the  obliterated  hypogastric  artery,  d'escends  upon  the  inner  side 
of  the  ureter  {u)  along  the  posterior  surface  to  the  base  of  the  bladder. 

The  base  or  fundus  (bas  fond ; inferior  fundus)  is  the  widest  and 
most  depending  part  of  the  bladder,  and  demands  special  attention. 
It  is  directed  somewhat  backwards  as  well  as  downwards,  and  differs 
in  its  relations  to  other  parts  according  to  the  sex.  In  the  male,  it 
rests  upon  the  second  portion  of  the  rectum  {b'),  and  is  covered  poste- 
riorly for  a short  space  by  the  peritoneum,  which,  however,  is  soon 

reflected  backwards  from  it  upon  the 


[Fig.  479. 


The  base  of  the  male  bladder,  with 


vesiculae  seminales  and  prostate  gland.  1. 
The  urinary  bladder.  2.  The  longitudinal 
layer  of  muscular  fibres.  3.  The  prostate 
gland.  4.  Membranous  portion  of  the  urethra. 
5.  The  ureters.  6.  Blood-vessels.  7.  Left; 
8.  Right  vas  deferens,  9.  Left  seminal  vesicle 
in  its  natural  position.  10.  Ductus  ejacula- 
toriusof  the  left  side  traversing  the  prostate 
gland.  11.  Right  seminal  vesicle  injected 
and  unravelled.  12.  13.  Blind  pouches  of 
vesiculae.  14.  Right  ductus  ejaculatorius 
traversing  the  prostate. — (Haller.)] 


rectum,  so  as  to  form  the  recto-vesical 
pouch  or  cul-de-sac  (/).  In  front  of 
the  line  of  reflection  of  the  serous 
membrane,  the  base  of  the  bladder 
presents  a triangular  surface,  desti- 
tute of  peritoneum,  and  separated 
from  the  rectum  by  some  dense  fibro- 
cellular  tissue  only,  which  adheres 
to  both  organs.  This  triangular  sur- 
face (fig.  479),  is  bounded  at  the 
sides  by  the  vasa  deferentia  (^)  and 
vesiculas  seminales  (®),  which  are 
here  firmly  attached  to  the  bladder, 
as  they  converge  forwards  to  the 
prostate  gland  (®);  behind,  it  is  limit- 
ed (at  the  lower  line^)  by  the  reflec- 
tion of  the  peritoneum  at  the  cul-de- 
sac,  whilst  its  apex  in  front  touches 
the  prostate  gland.  It  is  in  this 
space,  which  in  the  natural  state  of 
the  part  is  by  no  means  so  large  as 
it  appears  after  they  are  disturbed 
in  disseclion,  that  the  bladder  may 
be  punctured  from  the  rectum  with- 
out injury  to  the  peritoneum.  In  the 


THE  BLADDER. 


521 


female,  the  base  of  the  bladder  is  of  less  extent,  and  does  not  reach 
so  low  down  in  the  pelvis  as  in  the  naale ; for  it  rests  against  the  lower 
part  of  the  anterior  surface  of  the  uterus  and  the  anterior  wall  of  the 
vagina,  both  of  which  organs  intervene  between  it  and  the  rectum. 
This  part  of  the  bladder  adheres  to  the  vagina,  but  the  peritoneum 
forms  a pouch  between  it  and  the  uterus. 

The  cervix  or  neck  of  the  bladder,  situated  at  the  lower  part  of  the 
anterior  surface,  and  immediately  in  front  of  the  base,  is  the  con- 
stricted portion  which  is  directly  continuous  wdth  the  urethra.  In  the 
female  it  is  free,  being  merely  surrounded  by  cellular  tissue  and  blood- 
vessels, but  in  the  male  it  becomes  encircled  by  the  prostate  gland. 
In  the  male  also,  it  is  nearly  horizontal,  or  even  slightly  oblique  in  an 
upward  direction,  owing  to  the  fundus  of  the  bladder  being  on  a some- 
what lower  level,  but  in  the  female  its  direction  is  obliquely  downwards 
and  forwards,  for  the  cervix  is  the  low'est  part  of  the  female  bladder, 
and  such  is  also  the  case  in  male  infants.  The  neck  of  the  bladder  is 
supported  in  front  and  at  the  sides  by  the  vesical  fascia. 

Ligaments  of  the  bladder. — The  true  ligaments  of  the  bladder,  four 
in  number,  twm  anterior  and  two  lateral,  are  all  derived  from  the  vesi- 
cal portion  of  the  recto-vesical  fascia.  The  anterior  ligaments,  one 
right,  the  other  left,  are  two  strong  whitish  bands,  which  pass  from 
the  back  of  the  pubes  to  the  front  of  the  neck  and  lower  part  of  the 
anterior  surface  of  the  bladder.  A few  of  the  pale  vesical  muscular 
fibres  are  prolonged  into  them,  and  hence  they  are  considered  by 
some  as  tendons  of  attachment  for  the  muscular  fibres  of  the  bladder. 
In  the  male,  these  anterior  ligaments  {pubo-prostatic  ligaments),  in 
passing  backwards,  first  reach  the  upper  surface  of  the  prostate  and 
cover  in  the  anterior  fibres  of  the  levatores  ani,  which  spread  out  on 
that  gland  and  form  the  levatores  prostate.  Between  the  two  liga- 
ments is  a cellular  interval,  in  which  are  found  the  dorsal  vein  of  ihe 
penis,  or  of  the  clitoris.  The  lateral  ligaments,  much  broader  and 
thinner  than  the  anterior,  are  the  lateral  portions  of  the  vesical  fascia, 
which  proceed  inwards  to  be  fixed  to  the  neck  and  side  of  the  bladder, 
and  (in  the  male)  to  the  side  of  the  prostate. 

Peritoneal  folds  or  false  ligaments. — These  are  five  in  number. 
Two  of  them,  named  posterior  false  ligaments,  or  recto-vesical  folds, 
(plicfe  semilunares,  Douglas,)  run  forward  in  the  male  along  the  sides 
of  the  rectum  to  the  posterior  and  lateral  aspect  of  the  bladder,  curv- 
ing upwards  when  this  latter  is  distended,  and  bounding  the  sides  of 
the  recto-vesical  cul-de-sac  of  the  peritoneum.  In  the  female,  these 
posterior  folds  pass  forward  from  the  sides  of  the  uterus,  and  are 
comparatively  small.  The  two  lateral  false  ligaments  extend  from  the 
iliac  fossae  to  the  sides  of  the  bladder;  the  superior  false  ligament 
(ligamentum  suspensorium)  formed  by  the  projection  of  the  ascending 
part  of  the  epigastric  arteries  and  the  urachus,  into  a duplicature  of 
the  peritoneum,  reaches  from  the  summit  of  the  bladder  to  the  umbi- 
licus. 

Internal  surface. — On  opening  the  bladder  its  internal  surface  is 
found  to  be  lined  by  a smooth  membrane,  which  is  so  loosely  attached 
to  the  other  coats,  that  in  the  flaccid  condition  of  the  organ  it  is 

44* 


522 


FIBRES  OF  THE  BLADDER. 


nearly  everywhere  thrown  into  small  wrinkles  or  folds,  which  disap- 
pear so  soon  as  the  bladder  is  distended.  Besides  these,  the  interior 
of  the  bladder  is  often  marked  by  reticular  elevations  or  ridges,  cor- 
responding with  the  fasciculi  of  the  muscular  coat. 

At  the  lower  and  anterior  part  of  the  bladder  is  seen  the  orifice 
leading  from  its  neck  into  the  urethra,  around  which  the  mucous 
membrane  is  corrugated  longitudinally  (see  fig.  484).  Immediately 
behind  the  urethral  opening,  at  the  anterior  part  of  the  fundus,  is  a 
small  smooth  triangular  surface,  having  its  apex  turned  forwards, 
which,  owing  to  the  firmer  adhesion  of  the  mucous  membrane  to  the 
subjacent  tissues,  never  presents  any  rugae,  even  when  the  bladder  is 
empty.  This  surface  is  named  the  trigone  (trigone  vesical;  trigonum 
vesicas,  Lieutaud) ; at  its  posterior  angles  are  the  orifices  of  the  two 
ureters,  situated  about  If  inch  from  each  other,  and  about  inch 
from  the  anterior  angle,  which  corresponds  with  the  opening  into  the 
urethra.  At  the  last-named  point  is  found  a slight  elevation  of  the 
mucous  surfiice,  named  the  uvula  vesiccB  (luette  vesicale),  which  pro- 
jects from  below  into  the  urethral  orifice.  In  the  female,  the  trigone 
is  small,  and  the  uvula  indistinct.  In  the  male,  this  last-named  eleva- 
vation  lies  a little  in  advance  of  the  middle  lobe  of  the  prostate,  and  is 
sometimes  prolonged  on  the  floor  of  the  prostatic  portion  of  the  urethra. 
It  is  formed  by  a thickening  of  the  submucous  tissue.  It  can  scarcely 
act  as  a valve  to  the  urethral  orifice,  but  it  is  sometimes  very  much 
enlarged,  and  then  obstructs  that  passage. 

The  sides  of  the  trigone,  especially  when  the  muscular  coat  of  the 
bladder  is  strong,  are  bounded  by  tw'o  slight  ridges,  which  pass 
obliquely  backwards  and  outwards  to  the  orifices  of  the  ureters,  and 
indicate  the  course  of  two  small  bundles  of  muscular  fibres.  A pro- 
longation of  each  of  these  ridges  beyond  the  openings  of  the  ureters  is 
sometimes  seen,  caused,  it  would  appear,  merely  by  the  lower  ends  of 
those  canals,  as  they  pass  obliquely  through  the  parietes  of  the  bladder. 
The  posterior  boundary  of  the  trigone  is  slightly  curved,  its  concavity 
being  directed  backwards. 

Structure. — The  bladder  is  composed  of  a serous,  a muscular,  and  a 
mucous  coat,  united  together  by  cellular  tissue,  and  supplied  with 
vessels  and  nerves. 

The  serous  or  peritoneal  coat  is  a partial  covering,  investing  only 
the  posterior  and  upper  half  of  the  bladder,  and  reflected  from  its 
summit,  sides,  and  under  surface,  in  the  manner  already  described  in 
detail. 

The  muscular  coat. — This  consists  of  bundles  of  pale  unstriped 
involuntary  muscular  fibres,  which  are  arranged  in  two  principal  but 
imperfect  layers,  distinguished,  from  their  position  and  direction,  into 
the  external  or  longitudinal,  and  the  internal,  transverse  or  circular. 

The  external  or  longitudinal  fibres  are  most  distinctly  marked  on 
the  anterior  and  posterior  surfaces  of  the  bladder.  Commencing  in 
front  from  the  neck  of  the  organ,  from  the  anterior  true  ligaments, 
and,  in  the  male,  from  the  adjoining  part  of  the  prostate  gland,  they 
may  be  traced  upwards  along  the  anterior  surface  to  the  summit  of 
the  bladder,  whence  they  may  be  followed  down  over  the  posterior 


FIBRES  OF  THE  BLADDER. 


523 


surface  and  base  to  the  under  part  of  the  neck  of  the  bladder,  where 
they  become  attached  to  the  prostate  in  the  male,  and  to  the  front  of 
the  vagina  in  the  female.  Upon  the  sides  of  the  bladder  the  longi- 
tudinal fasciculi  run  more  or  less  obliquely,  and  often  intersect  one 
another:  in  the  male  they  reach  the  sides  of  the  prostate.  At  the 
summit  a few  are  continued  along  the  urachus.  The  longitudinal 
fibres,  taken  together,  constitute  what  has  been  named  the  detrusor 
urince  muscle. 

The  internal  or  circular  fibres  are,  for  the  most  part,  transverse, 
but,  upon  the  body  of  the  bladder  are  scattered  very  thinly  and  irregu- 
larly, having  various  arrangements  in  different  bladders.  Towards 
the  lower  part  of  the  organ,  they  assume  a more  decidedly  circular 
course,  and  upon  the  fundus  and  trigone  form  a tolerably  regular 
layer.  Close  to  and  around  the,  cervix,  immediately  behind  the 
prostate  in  the  male,  they  densely  encircle  the  orifice,  and  constitute 
what  has  been  named  the  sphincter  vesicce,  which,  however,  is  not 
distinct  from  the  other  circular  fibres. 

[According  to  Dr.  Homer,  the  inferior  semi-circumference  of  the  neck  of  the 
bladder  is  defined  by  a thick  fasciculus  of  muscular  (?)  fibre,  having  a texture 
resembling  that  of  the  middle  coat  of  the  arteries.  The  fasciculus  is  half  an  inch 
wide,  passes  transversely  above  the  third  lobe  of  the  prostate  gland,  and  has  its 
extremities  attached  to  the  lateral  lobes  of  the  latter.  The  superior  semi-circum- 
ference is  surrounded  by  a layer  of  muscular  fibres,  forming  a broad  thin  cres- 
centic band,  the  extremities  of  which  are  downwards,  and  are  insensibly  lost  by 
their  divergence  in  the  external  layer  of  the  general  muscular  investment  of  the 
bladder.*  The  elastic  character  of  the  transverse  fasciculus  in  a state  of  rest  Will 
keep  the  orifice  of  the  neck  of  the  bladder  closed,  while  the  muscular  fibres,  in 
the  general  contraction  of  the  muscular  coat  of  the  bladder,  it  is  to  be  presumed, 
will  stretch  the  band,  and  in  this  manner  open  the  orifice. — J.  L.] 

The  muscles  of  the  ureters  are  the  two  muscular  bundles,  sometimes 
more  clearly  seen  than  at  others  (and  especially  in  male  subjects), 
which  pass  obliquely  from  behind  the  opening  of  the  urethra,  or  from 
the  uvula,  backwards  and  outwards  to  the  orifices  of  the  ureters.  In 
the  male,  these  bundles  meet  behind  the  prostate,  and  there  end  by 
fibrous  tissue  in  the  middle  lobe  of  that  gland.  They  w'ere  known  to 
Morgagni,  but  have  more  recently  been  fully  described  under  the 
name  of  the  “ muscles  of  the  ureters”  by  Sir  C.  Bell,  who  supposed 
that,  during  the  contraction  of  the  bladder,  they  might  maintain  the 
due  obliquity  of  the  lower  end  of  the  ureters,  necessary  to  prevent 
reflux  of  urine  into  these  tubes ; others  have  thought  that  they  might 
facilitate  the  flow  of  urine  into  the  bladder  by  stretching  the  ureters 
and  their  orifice  downwards. 

The  muscular  coat  of  the  bladder  forms  so  incomplete  a covering, 
that  when  the  organ  is  much  distended,  intervals  arise  in  w'hich  the 
walls  of  the  organ  are  very  thin ; and  should  the  internal  or  mucous 
lining  protrude  in  any  spot  through  the  muscular  bundles,  a sort  of 
hernia  is  produced,  which  may  go  on  increasing,  so  as  to  form  what 
is  called  a vesical  sacculus,  or  appendix  vesicce,  the  bladder  thus 
affected  being  termed  sacculated.  Hypertrophy  of  the  muscular  fas- 
ciculi, which  is  liable  to  occur  in  stricture  of  the  urethra  or  other 

* [Spec.  Anat.  and  Hist.,  vol.  ii.  p.  103.  Philadelphia,  1846.] 


524 


THE  URETHRA. 


affections  impeding  the  issue  of  the  urine,  gives  rise  to  that  condition 
named  \\\e  fasciculated  bladder,  in  which  the  interior  of  the  organ  is 
marked  by  strong  reticulated  ridges  or  columns. 

Next  to  the  muscular  coat,  between  it  and  the  mucous  membrane, 
but  much  more  intimately  connected  with  the  latter,  is  a well-marked 
layer  of  cellular  tissue,  frequently  named  the  cellular,  or  vascular  coat. 
This  submucous  cellular  layer  contains  a large  quantity  of  very  fine 
coiled  fibres  of  elastic  tissue. 

The  mucous  membrane  of  the  bladder  is  soft,  smooth,  and  of  a pale 
rose-colour.  It  is  continuous  above  with  that  of  the  ureters  and 
kidneys,  and  below  with  that  lining  the  urethra.  It  adheres  but 
loosely  to  the  muscular  tissue,  except  at  the  trigone,  where  it  is  in 
consequence  always  smooth.  There  are  no  villi  upon  the  vesical 
mucous  membrane,  but  it  is  provided  with  minute  follicles,  which  are 
most  abundant  in  the  vicinity  of  the  neck  of  the  bladder.  It  is  covered 
with  an  epithelium,  the  particles  of  which  are  intermediate  in  form 
between  those  of  the  columnar  and  squamous  varieties.  The  vesical 
mucus  (according  to  Mandl)  is  alkaline,  and  appears  to  contain 
alkaline  and  earthy  phosphates. 

Vessels. — The  superior  vesical  arteries  are  the  remaining  pervious 
portions  of  the  hypogastrics ; in  the  adult  they  appear  as  branches  of 
the  internal 'Iliac.  The  inferior  vesical  arteries  are  usually  derived 
from  the  anterior  division  of  the  internal  iliac.  The  uterine  arteries 
also  send  branches  to  the  bladder  in  the  female.  The  neck  and  base 
of  the  organ  appear  to  be  the  most  vascular  portions.  The  veins  form 
large  plexuses  around  the  neck,  sides,  and  base  of  the  bladder;  they 
eventually  pass  into  the  internal  iliac  veins.  The  lymphatics  follow  a 
similar  course.  The  nerves  are  derived  partly  from  the  hypogastric 
plexus  of  the  sympathetic,  and  partly  from  the  sacral  plexus  of  the 
cerebro-spinal  system.  The  former  are  said  to  be  chiefly  distributed 
to  the  upper  part  of  the  bladder,  whilst  the  spinal  nerves  may  be  traced 
to  its  neck  and  base. 

THE  URETHRA. 

The  urethra  is  a membranous  tube  directed  in  the  median  line  from 
behind  forwards,  beneath  the  arch  of  the  pubes ; by  one  extremity  it  is 
continuous  with  the  neck  of  the  bladder,  by  the  other  it  opens  exter- 
nally. In  \\\e  female,  it  serves  simply  as  the  excretory  passage  for  the 
urine;  in  the  male,  it  conducts  also  the  seminal  fluid. 

a.  The  female  urethra,  as  compared  with  that  of  the  other  sex,  is 
very  short,  representing  only  the  commencing  part  of  the  male 
passage.  It  is  only  about  an  inch  and  a half  in  length,  but  is  wide 
and  capable  of  great  distension ; its  ordinary  diameter  is  about  three 
or  four  lines,  but  it  enlarges  towards  its  vesical  orifice.  The  direction 
of  this  canal  is  downwards  and  forwards,  and  it  is  slightly  curved  and 
concave  upwards.  It  lies  erribedded  in  the  upper  or  rather  the  anterior 
wall  of  the  vagina,  from  which  it  cannot  be  separated  ; the  two  pas- 
sages both  perforate  the  triangular  ligament ; the  upper  one,  or  urethra, 
is  covered  by  the  anterior  ligament  of  the  bladder. 

The  external  orifice,  or  meatus  urinarius,  opens  in  the  vulva,  beneath 


THE  URETHRA. 


525 


the  symphysis  pubis,  nearly  an  inch  below  and  behind  the  clitoris, 
between  the  nymphee  and  immediately  above  the  entrance  to  the 
vagina.  It  will  be  again  noticed  with  the  other  parts  in  the  vulva. 
From  its  orifice,  which  is  the  narrowest  part  of  the  canal,  it  passes 
upwards  and  backwards  between  the  crura  of  the  clitoris  and  behind 
the  pubes,  gradually  enlarging  into  a funnel-shaped  opening  as  it 
approaches  and  joins  the  neck  of  the  bladder.  There  is  also  a dilata- 
tion in  the  floor  of  the  canal,  just  within  the  meatus. 

The  mucous  membrane  is  whitish,  except  near  the  orifice ; it  is 
raised  into  longitudinal  plicae,  which  are  not  entirely  obliterated  by 
distension,  especially  one  which  is  particularly  marked  on  the  lower 
or  posterior  surface  of  the  urethra.  Near  the  bladder  the  membrane 
is  soft  and  pulpy,  with  many  tubular  mucous  glands.  Lower  down 
these  increase  in  size  and  lie  in  groups,  between  the  longitudinal  folds, 
and  immediately  within  and  around  the  orifice,  the  lips  of  which  are 
elevated,  are  several  larger  and  wider  crypts. 

The  lining  membrane  is  covered  with  a scaly  epithelium,  but  higher 
up  near  the  bladder  the  particles  become  spheroidal.  The  submucous 
cellular  tissue  contains  elastic  fibres.  Outside  this  there  is  a highly 
vascular  structure,  in  which  are  many  large  veins.  Between  the 
anterior  and  posterior  layers  of  the  triangular  ligament,  the  female 
urethra  is  embraced  by  the  fibres  of  the  compressor  urethrae  muscle, 
which  will  be  hereafter  described  (p.  538). 

The  vessels  and  verves  of  the  female  urethra  are  very  numerous, 
and  are  derived  from  the  same  sources  as  those  of  the  vagina. 

h.  The  male  urethra  is  much  longer,  and  its  anatomy  more  com- 
plex ; from  its  additional  function  and  anatomical  connexions,  the  de- 
scription of  it  is  most  conveniently  associated  with  that  of  the  organs 
of  generation. 


ORGANS  OF  GENERATION. 


THE  MALE  ORGANS  OF  GENERATION. 

The  male  organs  of  generation  consist  of  the  testes  and  their  excre- 
tory apparatus,  the  prostate  and  Coivper’s  glands,  and  the  penis,  with 
the  urethra  or  genito-urinary  passage. 

Taking  the  organs  according  to  their  local  connexion  with  parts 
previously  described,  rather  than  in  a physiological  order,  we  com- 
mence with 


THE  PROSTATE  GLAND. 

The  prostate  gland  (from  ■tfgoifl'T-iiiJ.i,  to  stand  before  ; fig.  478,  p)  is  a 
firm  glandular  body,  very  much  resembling  a chestnut  in  shape  and 
size,  which  surrounds  the  neck  of  the  bladder  and  the  commencement 
of  the  urethra,  and  is  placed  in  the  pelvic  cavity,  between  and  below 
the  pubes  and  behind  the  triangular  ligament.  It  has  been  compared 
to  a truncated  cone,  compressed  from  above  downwards,  having  its 
broader  part  or  base  turned  backwards  and  upwards  towards  the  neck 
of  the  bladder,  and  its  blunted  apex  in  the  opposite  direction  tow’ards 
the  membranous  part  of  the  urethra.  It  usually  measures  about  an 
inch  and  a half  across  at  its  widest  part,  an  inch  or  rather  more  from 
its  base  to  its  apex,  and  about  three  quarters  of  an  inch  in  depth  or 
thickness.  Its  ordinary  weight  is  about  six  drachms. 

The  anterior  or  upper  surface  of  the  prostate  is  flattened  and  marked 
with  a slight  longitudinal  furrow : it  is  about  half  an  inch  or  rather 
more  beneath  the  pubic  symphysis,  and,  as  well  as  the  sides  of  the 
gland,  is  connected  to  the  pubic  arch  by  a reflection  of  the  pelvic 
fascia,  forming  the  pubo-prostatic  ligaments  or  anterior  ligaments  of 
the  bladder.  The  posterior  or  under  surface  (fig.  479)  is  smooth,  and 
is  marked  by  a slight  depression,  or  by  two  grooves,  which  meet  in 
front,  and  correspond  with  the  course  of  the  seminal  ducts,  as  well  as 
mark  the  limits  of  the  lateral  lobes  in  this  situation ; it  is  closely 
united  to  the  rectum,  just  before  the  bowel  turns  downwards  to  reach 
the  anus,  by  means  of  cellular  membrane,  which  is  destitute  of  fat ; so 
that  this  surface  of  the  gland  and  also  its  posterior  border,  can  be  felt 
by  the  finger  introduced  into  the  intestine.  The  sides  are  convex  and 
prominent,  and  are  slung  as  it  were  by  the  anterior  portions  of  the 
levatores  ani  muscles,  which  pass  down,  on  either  side,  from  the 
symphysis  pubis  and  anterior  ligament  of  the  bladder,  and  spread  out 
on  the  sides  of  the  prostate.  This  part  of  each  levator  ani  is  occa- 
sionally separated  from  the  rest  of  the  muscle  by  cellular  tissue;  it  has 
been  named  levator  prostalce  (p.  472).  The  base  of  the  gland  is  of 
considerable  thickness,  and  is  notched  in  the  middle:  its  apex  is  turned 


THE  PROSTATE  GLAND. 


527 


towards  the  triangular  ligament.  As  already  stated,  the  prostate 
encloses  part  of  the  neck  of  the  bladder  and  the  commencement  of  the 
urethra.  The  canal  runs  nearer  to  the  upper  than  to  the  under  sur- ' 
face  of  the  gland,  so  that  in  general  it  is  about  two  lines  distant  from 
the  former  and  four  from  the  latter;  but  it  frequently  differs  greatly  in 
this  respect.  The  prostatic  portion  of  the  urethra  is  about  an  inch  and 
a quarter  long,  and  is  dilated  in  the  middle ; it  contains  the  verumon- 
tanum  and  the  openings  of  the  seminal  and  prostatic  ducts,  to  be  after- 
wards noticed.  The  common  seminal  ducts,  which  pass  forwards 
from  the  vesiculee  seminales,  also  go  through  the  lower  part  of  the 
prostate,  enclosed  in  a special  canal,  and  open  into  the  urethra.  This 
gland  is  usually  described  as  consisting  of  three  lobes,  two  of  which 
placed  laterally  and  separated  behind  by  the  posterior  notch,  are  of 
equal  size  ; the  third,  or  middle  lobe,  is  a smaller  rounded  or  triangular 
mass,  intimately  connected  with  the  other  two,  and  fitted  in  between 
them  on  the  under  side,  lying  beneath  the  neck  of  the  bladder  and  ihe 
immediately  adjacent  part  of  the  urethra.  This  third  lobe  is  exposed 
by  turning  down  the  seminal  vesicles  and  ducts,  between  which  and 
the  cervix  vesicse  it  is  placed.  When  rather  prominent  in  the  bladder, 
it  corresponds  to  the  elevation  already  described  in  that  organ,  and 
named  the  uvula  vesicre ; and  when  much  enlarged,  it  projects  in  such 
a way  as  to  impede  or  prevent  the  evacuation  of  the  urine. 

Structure. — The  prostate  is  enclosed  in  a dense  fibrous  coat,  which 
is  continuous  with  the  recto-vesical  fascia  and  with  the  posterior  layer 
of  the  triangular  ligament,  and  is  rather  difficult  either  to  tear  or  cut. 
Mr.  Adams  describes  the  fibrous  capsule  as  divisible  into  two  layers, 
between  which  the  prostatic,  plexus  of  veins  is  enclosed.*  The  sub- 
stance of  the  gland  is  spongy  and  more  yielding  ; its  colour  is  reddish 
gray,  or  sometimes  of  a brownish  hue.  It  consists  of  numerous  small 
follicles  or  terminal  vesicles  opening  into  elongated  canals,  which 
unite  into  a smaller  number  of  excretory  ducts.  These  appear  as 
pores  or  whitish  streaks,  according  to  the  way  in  which  they  are 
exposed  on  a section.  The  epithelium  in  the  vesicular  terminations  is 
thin  and  squamous,  whilst  in  the  canals  it  is  columnar.  Thecapillary 
blood-vessels  spread  out  as  usual  on  the  ducts  and  clusters  of  vesicles, 
and  their  different  elements  are  united  by  areolar  tissue,  and  supported 
by  processes  of  the  deep  layer  of  the  fibrous  capsule  (Adams).  The 
ducts  open  by  from  twelve  to  twenty  or  more  orifices  upon  the  floor 
of  the  urethra,  as  will  presently  be  noticed,  together  with  other  parts 
to  be  seen  in  the  prostatic  portion  of  that  canal. 

Vessels  and  Nerves. — The  prostate  is  supplied  by  branches  of  the 
vesical,  hemorrhoidal,  and  pudic  arteries.  Its  veins  form  a plexus 
around  the  sides  and  base  of  the  gland,  w'hich  is  particularly  marked 
in  old  subjects.  These  veins  communicate  in  front  with  the  dorsal 
vein  of  the  penis,  and  behind  with  branches  of  the  internal  iliac  vein. 
According  to  Mr.  Adams,  the  lymphatics,  like  the  veins,  are  seen 
ramifying  between  the  two  layers  of  the  fibrous  capsule.  The  nerves 
are  derived  from  the  hypogastric  plexus. 


Cyclop,  of  Anat.,  vol.  iv.,  p.  147. 


528 


THE  PENIS. 


Prosfatic  fliiiil. — This  is  mixed  with  the  seminal  fluid  during  emission;  as  ob- 
tained from  the  human  prostate  soon  after  death,  it  has  a milky  aspect,  which  is 
ascribed,  by  Mr.  Adams,  to  the  admixture  of  a large  number  of  epithelial  cells, 
and  he  thinks  it  probable  that,  as  discharged  during  life,  it  is  more  transparent. 
According  to  the  same  observer,  the  prostatic  fluid  has  an  acid  reaction,  and  pre- 
sents, under  the  microscope,  numerous  molecules,  epithelial  particles,  both  squa- 
mous and  columnar,  and  granular  nuclei,  about  inch  in  diameter.  As  age 
advances,  this  gland  is  disposed  to  become  enlarged ; and  its  ducts  often  con- 
tain small  round  concretions  about  the  size  of  a millet  seed,  which  are  composed 
of  carbonate  of  lime  and  animal  matter. 

THE  PENIS. 

The  penis,  which  supports  the  greater  part  of  the  urethra  in  the 
male,  is  composed  principally  of  an  erectile  tissue,  occupying  three 
long  and  nearly  cylindrical  compartments,  or  forming  three  bodies 
(corpora),  as  they  are  termed.  Of  these,  two,  named  corpoi'a  caver- 
nosa penis,  placed  side  by  side,  form  the  principal  part  of  the  organ, 
whilst  the  other,  situated  behind  or  beneath  the  two  preceding,  sur- 
rounds the  canal  of  the  urethra ; it  is  hence  named  corpus  cavernosum 
urethrce  or  corpus  spongiosum.. 

The  penis  is  attached  behind  to  the  front  of  the  pubes,  and  to  the 
pubic  arch,  by  what  is  termed  the  root;  in  front  it  ends  in  an  enlarge- 
ment named  \he  glans.  The  intermediate  portion  or  body  of  the  penis, 
owing  to  the  relative  position  of  its  three  compartments,  has  three 
sides,  and  three  rounded  borders  ; its  widest  side  is  turned  upwards 
and  forwards,  and  is  named  the  dorsum.  The  entire  organ  is  invested 
by  the  common  integument,  which  will  be  immediately  noticed.  The 
glans  penis,  which  is  slightly  compressed  above  and  below,  presents 
at  its  summit  a vertical  fissure,  the  external  orifice  of  the  urethra  ; its 
base,  which  is  wider  than  the  body  of  the  penis,  forms  a rounded  pro- 
jecting border,  named  the  corona  glandis,  behind  which  is  a constric- 
tion named  the  cervix ; the  posterior  boundary  of  the  glans  thus  marked 
oti’ passes  down  on  each  side  of  the  under  surface,  and  ends  behind 
the  urethral  opening,  on  the  sides  of  a median  fold  of  skin,  named  the 
frcenum. 

The  integuments. — The  prepuce  ov  foreskin  (prreputium)  is  a loose 
circular  fold  of  skin,  which  is  attached  around  the  penis  behind  the 
cervix,  and  covers  the  glans.  The  integument  of  the  penis,  which  is 
continued  from  that  upon  the  pubes  and  scrotum,  forms  a close  and 
simple  investment,  as  far  as  the  neck  of  the  glans.  At  this  part  it 
leaves  the  surface  and  is  doubled  up  to  form  the  prepuce.  The  inner 
layer  of  this  fold  returns  to  the  penis  behind  the  cervix,  where  it  is 
firmly  attached,  and  becoming  thus  again  adherent,  is  continued  for- 
wards over  the  corona  and  glans,  as  far  as  the  orifice  of  the  urethra, 
where  it  meets  with  the  mucous  membrane  of  the  urethra,  and  behind 
that  orifice  forms  the  fraenum  of  the  prepuce.  Upon  the  body  of  the 
penis  the  skin  is  very  thin,  entirely  free  from  fat,  and,  excepting  at  the 
root,  from  hairs  also,  in  these  respects  differing  remarkably  from  that 
on  the  pubes,  which  is  thick,  covers  a large  cushion  of  fat,  and,  after 
puberty,  is  beset  with  hairs:  the  skin  of  the  penis  is  moreover  very 
movable  and  distensible,  and  is  dark  in  colour.  At  the  free  margin  of 
the  prepuce  the  integument  changes  its  character,  and  approaches  to 


THE  CORPORA  CAVERNOSA. 


529 


that  of  a mucous  membrane,  being  red,  thin,  and  moist.  Numerous 
lenticular  glands  are  collected  around  the  cervix  of  the  penis  and 
corona ; they  are  named  the  glands  of  Tyson  (glandulas  Tysoni,  vel 
odoriferee),  and  secrete  a sebaceous  matter  of  a peculiar  odour 
{smegma  praputii),  which  appears  to  contain  caseine,  and  easily  runs 
into  decomposition.  Upon  the  glans  penis  the  membrane  again 
changes  its  character;  it  ceases  to  contain  glands,  but  its  papillee  are 
highly  developed  and  extremely  sensitive,  and  it  adheres  most  inti- 
mately and  immovably  to  the  spongy  tissue  of  the  glans. 

Beneath  the  skin,  on  the  body  of  the  penis,  the  ordinary  superficial 
fascia  is  very  distinct ; it  is  continuous  with  that  of  the  groin,  and 
also  with  the  dartoid  tissue  of  the  scrotum.  Near  the  root  of  the 
organ  there  is  a dense  band  of  fibro-elastic  tissue,  named  the  suspen- 
sory ligament,  lying  amongst  the  fibres  of  the  superficial  fascia ; it  is 
triangular  in  form  ; one  edge  is  free,  another  is  connected  with  the 
fore  part  of  the  pubic  symphysis,  and  the  third  to  the  dorsum  of  the 
penis,  with  the  fibrous  structures  of  which  it  is  blended  opposite  the 
divergence  of  the  two  corpora  cavernosa. 

The  integuments  of  the  penis  are  supplied  with  blood  by  branches 
of  the  dorsal  artery  of  the  penis  and  external  pudic ; the  veins  join  the 
dorsal  and  external  pudic  veins. 

THE  CORPORA  CAVERNOSA. 

The  corpora  cavernosa  form  the  principal  part  of  the  body  of  the 
penis,  and  necessarily  determine  its  form  and  consistence;  and  it  is 
owing  to  the  changes  which  can  take  place  in  the  erectile  tissue 
within  them,  that  the  size  and  direction  of  the  organ  undergo  such 
great  alterations.  The  two  corpora  cavernosa,  which  exactly  corre- 
spond, represent  two  cylindrical  or  rather  fusiform  bodies,  placed  side 
by  side,  flattened  on  their  median  aspects,  and  intimately  blended  to- 
gether along  the  middle  line,  for  the  anterior  three-fourths  of  their 
length,  whilst  at  the  back  part  they  separate  from  each  other  in  form 
of  two  tapering  processes  named  crura  (fig.  480,  c,  c),  the  whole 
somewhat  resembling  the  capital  letter  Y.  Commencing  behind  by  a 
pointed  extremity  somewhat  above  the  tuberosities  of  the  ischia  (d), 
these  crura  become  gradually  enlarged,  and  are  attached,  one  on 
each  side,  to  the  rami  of  the  ischia  and  pubes;  continuing  to  ascend, 
and  then  advancing  from  the  bones,  they  approach  and  speedily  be- 
come united  to  each  other  at  the  root  of  the  penis.  Immediately 
before  their  union  each  of  them  sw’ells  into  a slight  enlargement  {g  to 
g),  so  as  to  form,  what  are  named  by  Kobelt,  the  bulbs  of  the  corpora 
cavernosa,  parts  which  are  embraced  by  the  erectores  penis  muscles 
(d),  and  which  attain  a much  greater  proportionate  development  in 
some  quadrupeds.  Beyond  this  point  they  are  again  slightly  con- 
stricted, and  are  joined  firmly  together  along  the  middle  line  to  form 
the  body  of  the  penis,  and  finally  becoming  smaller  and  somewhat 
pointed  again  in  front,  are  completely  fused  together  into  a single 
anterior  rounded  extremity,  which  is  covered  by  the  glans  penis  and 
closely  connected  to  its  base. 

The  under  surface  of  the  united  cavernous  bodies  presents  a deep 
VOL.  IX.  45 


530 


THE  CORPORA  CAVERNOSA. 


longitudinal  groove,  in  which  is  lodged  the  corpus  spongiosum  (f), 
containing  the  greatest  part  of  the  canal  of  the  urethra.  ° The  upper 
or  anterior  surface  is  also  marked  with  a slight  median  groove  for  the 
dorsal  vein  of  the  penis,  and  near  the  root  is  attached  to"" the  pubes  by 
the  suspensory  ligament. 


Fig.  480. 


[Fig.  481. 


Fig.  480.  Part  of  the  ossa  pubis  and  isfiiia, 
with  the  rool  ol'tlie  penis  ailached  (Kobell). 
— a,  a.  Arceleralor  nrinae  nmsrle,  embracing 
the  bulb  of  the  urethra,  which  is  slightly 
notched  in  the  middle  line,  e,  behind,  b,  b. 
Anterior  slips  of  the  accelerator  muscle, 
which  pass  round  to  the  dorsum  of  the  penis, 
c,  c.  Crura  of  the  penis,  d,  d.  Erectores 
penis  muscles  lying  on  the  crura.  /.  The 
corpus  spongiosum  urethtfia.  g tog.  Enlarge- 
ment of  the  crus,  named  the  bulb  of  the 
corpus  cavernosum. 

[Fig.  481.  A seciiun  of  the  corpora  caver- 
nosa penis  (1),  and  corpus  spongiosum  ure- 
thrte  (4).  2.  Erectile  tissue  of  the  corpora  cavernosa.  3.  Septum  pectmiforiiie.  6.  Canal  of  the 
urethra.  6.  Internal  filaments  of  the  corpora  cavernosa  which  pass  from  the  median  septum  to 
the  external  fibrous  membrane. — S.  & H.] 


Structure. — A transverse  section  (fig.  481)  through  the  penis,  besides 
illustrating  the  structure  of  the  cavernous  bodies,  shows  their  form 
and  connexion  with  the  other  parts.  Above,  and  at  the  sides,  are 
seen  the  section  of  the  two  semi-cylindrical  cavernous  bodies  (', 
'),  bounded  by  a strong  fibrous  envelope,  containing  a mass  of  spongy 
erectile  tissue  in  their  interior,  and  separated  by  a vertical  fibrous 
septum  in  the  median  plane  (^).  Beneath  and  between  them  is  the 
other  erectile  mass,  named  the  corpus  spongiosum  (■*),  surrounding 
the  canal  of  the  urethra  (^). 

The  median  septum  is  thick  and  complete  behind,  where  the  two 
corpora  cavernosa  first  meet  each  other;  but  further  forward  it  be- 
comes thinner,  and  imperfectly  separates  their  two  cavities,  for  it 
presents,  particularly  towards  the  anterior  extremity,  numerous  clefts 
or  fissures,  extending  from  the  dorsal  to  the  urethral  edge  of  the  sep- 
tum, and  admitting  of  a free  communication  between  the  erectile 
tissue  of  the  two  sides.  From  the  direction  of  these  slits,  the  inter- 
mediate white  portions  of  the  septum  are  made  to  resemble  in  ar- 
rangement the  teeth  of  a comb,  and  hence  it  is  named  septum  pecti- 
niforme. 

The  external  fibrous  investment  of  the  cavernous  structure  is  white 


THE  CORPORA  CAVERNOSA. 


531 


and  dense,  from  half  a line  to  a line  thick,  and  very  strong  and  elastic. 
It  is  composed  for  the  most  part  of  longitudinal  bundles  of  shining  white 
fibres.  It  is,  perhaps,  the  strongest  fibrous  tunic  in  the  whole  body, 
but  yet  it  most  readily  admits  of  distension  up  to  a certain  point.  The 
septum  is  composed  of  the  same  kind  of  fibres. 

From  the  interior  of  the  fibrous  envelope,  and  from  the  sides  of  the 
septum,  numerous  lamellae,  bands  and  cords,  composed  also  of  an  ex- 
tensible fibrous  tissue,  and  named  trabecuIcB,  pass  inwards  and  run 
through  and  across  the  cavity  in  all  directions,  thus  subdividing  it 
into  a multitude  of  interstices,  and  giving  the  entire  structure  a spongy 
character.  Within  these  interstices  is  lodged  an  intricate  plexus  of 
veins,  into  which  the  arteries  open. 

a.  The  trabeculm,  whether  lamelliform  or  cord-like,  are  larger  and 
stronger  near  the  circumference  than  along  the  centre  of  each  cavern<jus 
body,  and  they  also  become  gradually  thicker  towards  the  crura.  The 
interspaces,  on  the  other  hand,  are  larger  in  the  middle  than  near  the 
surface,  and  also  become  larger  towards  the  fore  part  of  the  penis. 
The  trabeculae  contain  the  ordinary  white  fibrous  tissue  and  fine 
elastic  fibres.  A pale,  reddish  tissue  has  been  observed  in  them  by 
Muller  and  others,  wdiich  has  been  regarded  as  composed  of  involun- 
tary muscular  fibres ; this  tissue  is  much  more  abundant  in  the  penis 
of  the  horse  and  ass  : according  to  Muller,  it  resembles  muscular  sub- 
stance in  yielding  no  gelatine  on  boiling,  and  in  its  solution  in  acetic 
acid  being  precipitated  by  the  ferrocyanide  of  potassium. 

b.  The  veins  completely  fill  the  intertrabecular  spaces ; their  com- 
munications are  so  free  and  so  abundant  that  on  a section  the  caver- 
nous structure  appears  a labyrinth  of  intercommunicating  venous 
areolre  divided  by  the  trabecular  tissue.  The  walls  of  the  veins  are  very 
thin,  and  they  are  lined  by  a squamous  epithelium.  The  intertrabecular 
veins  of  the  two  sides  communicate  freely  through  the  septum,  espe- 
cially in  front;  but  not  directly  with  those  of  the  corpus  spongiosum  of 
the  urethra.  They  return  their  blood  partly  by  a series  of  branches  which 
escape  between  the  corpora  cavernosa  and  the  corpus  spongiosum, 
and  which,  accompanied  by  veins  from  the  latter,  mount  on  the  sides 
of  the  penis  to  the  vena  dorsalis  (p.  27),  partly  by  short  veins  issuing 
at  the  upper  surface,  and  immediately  joining  the  dorsal  vein,  but 
principally  by  veins  passing  out  near  the  root  of  the  penis  and  joining 
the  prostatic  plexus  and  pudendal  veins.  According  to  Kobelt,  there 
are  also  communications  with  the  cutaneous  veins  on  the  abdomen. 

c.  The  arteries  of  the  corpora  cavernosa  are  branches  of  the  pudic 
artery.  The  proper  cavernous  arteries  (profundae  penis),  right  and 
left,  supply  them  chiefly,  but  the  dorsal  artery  of  the  penis  also  sends 
twigs  through  the  fibrous  sheath,  along  the  upper  surface,  especially 
in  the  fore  part  of  the  penis  (vol.  i.  p.  615).  Kobelt  describes  a distinct 
small  branch  of  the  pudic  artery  which  enters  the  bulbous  enlargement 
of  each  corpus  cavernosum ; he,  moreover,  states  that  the  arteriae  pro- 
fundae  of  the  two  sides  form  an  anastomotic  arch,  from  which  the 
proper  cavernous  arteries  are  given  off.  Within  the  cavernous  tissue, 
the  numerous  branches  of  the  arteries  are  supported  by  the  trabeculae, 
in  the  middle  of  which  they  run  (fig.  482,  a).  There  is  some  uncer- 
tainty as  to  their  mode  of  termination,  but  it  is  generally  assumed  that 


532 


THE  HELICINE  ARTERIES. 


they  end  in  capillaries  wliich  open  into  minute  commencing  veins,  as 
in  other  parts.  Valentin,  however,  describes  the  minutest  arterial 
twigs  as  ending  by  rather  wide  funnel-shaped  orifices,  which  open  at 


Fig.  483. 


Fig.  482.  Portion  of  the  erectile 
tissue  of  the  corpus  cavernosum  mag- 
nified, to  show  the  areolar  structure 
and  the  distribution  of  the  arteries 
(Miiller).  a.  A small  artery,  sup- 
ported by  the  larger  trabeculte,  and 
branching  out  on  all  sides,  c.  The 
tendril-like  arterial  tufts,  or  helicine 
arteries  of  Muller,  d.  The  areolar 
structure  formed  by  the  finer  tra- 
beculse. 

Fig.  483.  A single  tuft  or  helicine 
arlery  projecting  into  a vein,  more 
highly  magnified  (Muller). 


once  into  the  venous  cavities ; but  this  has  not  been  confirmed.  Muller 
has  described  them  as  terminating  in  two  modes  : according  to  him, 
some  of  them,  which  he  considers  as  the  nutritive  arteries,  end  in  a 
capillary  network,  which  leads  in  the  usual  way  to  the  veins ; but 
others,  which  were  first  described  by  the  same  observer,  terminate  in 
an  entirely  different  and  peculiar  way.  Small  ramuscles,  he  says, 
consisting  of  short  tendril-like  branches  (c),  come  off  from  the  sides  of 
the  trabecular  arteries,  and  projecting  into  the  vein  so  as  to  be  covered 
by  its  lining  membrane,  end  abruplly  by  dilated  extremities  (fig.  48S). 
Sometimes  they  are  single,  and  sometimes  in  tufts;  he  has  named 
them  the  “helicine  arteries”  (arterise  helicime).  The  existence  of 
these  little  vessels  was  denied  strenuously  by  Valentin,  who  thought 
they  were  the  loose  flexuous  ends  of  the  vessels  of  the  smallest  tra- 
beculae coiled  up  by  the  retraction  of  the  latter  after  they  have  been 
broken  or  cut  across  in  making  a section.  They  may,  liowever,  be 
seen  in  the  deepest  cells,  which  have  not  been  affected  by  the  knife  ; 
and  the  observations  of  Krause,  Hyrll,  and  Erdl  appear  to  confirm  the 
original  statement  of  Muller,  as  far  at  least  as  regards  their  natural 
existence.  It  was  supposed  by  Muller  that  the  dilated  ends  of  these 
helicine  arteries  opened  into  the  venous  cavities,  and  Krause  also 
adopts  this  view ; but  no  opening  has  been  seen  in  them,  and  as  Muller 
himself  admits,  they  may  be  merely  arterial  diverticula.  They  are 
most  abundant  in  the  posterior  part  of  the  corpora  cavernosa,  and  are 
found  in  the  corresponding  part  of  the  corpus  spongiosum  also  ; but 
they  have  not  been  seen  in  the  glans  penis.  They  are  most  distinct  in 
man,  but  whatever  may  be  their  use,  they  do  not  appear  to  be  essential 
to  the  process  of  erection. 


CORPUS  SPONGIOSUM. 


5R3 

CORPUS  SPONGIOSUM. 

The  corpus  spongiosum  urethras  commences  in  front  of  the  triangular 
ligament  of  the  perineum,  between  the  diverging  crura  of  the  corpora 
cavernosa,  somewhat  behind  their  point  of  junction,  and  below  the 
membranous  portion  of  the  urethra,  by  an  enlarged  and  rounded  extre- 
mity named  the  bulb  (fig.  478,  e).  From  thence  it  extends  forwards 
as  a cylindrical,  or  slightly  tapering  body,  lodged  in  the  groove  on 
the  under  side  of  the  united  cavernous  bodies,  as  far  as  their  blunt 
anterior  extremity,  over  which  it  expands  so  as  to  form  the  glans  penis 
already  described. 

The  posterior  bulbous  extremity,  or  bulb  of  the  urethra  (figs.  478, 
480,  e),  varies  in  size  in  different  subjects.  It  receives  an  investment 
from  the  triangular  ligament,  and  is  embraced  by  the  accelerator 
urinae,  or  bulbo-cavernous  muscle  {a,  a).  The  canal  of  the  urethra 
(fig.  478,  c)  passes  into  the  bulb  behind  and  above,  so  that  the  latter 
projects  below  and  conceals  the  membranous  portion  of  that  canal. 
This  projecting  part  of  the  bulb  exhibits,  more  or  less  distinctly,  a sub- 
division into  two  lateral  portions  or  lobes,  between  which  a slight 
furrow  externally  and  a slender  fibrous  partition  internally  extends  for 
a very  short  distance  forwards:  in  early  infancy  this  is  more  marked. 
It  is  above  and  between  these  two  halves  that  the  urethra  enters,  sur- 
sounded  by  a portion  of  the  spongy  tissue,  named  by  Kobelt  the  colli- 
culus bulbi from  which  a layer  of  venous  erectile  tissue  passes  back  upon 
the  membranous  portion  of  the  urethra,  and  also  upon  tfie  prostatic 
part,  to  the  neck  of  the  bladder,  lying  closely  beneath  the  mucous 
membrane.  From  what  has  preceded,  it  will  be  evident  that,  at  first, 
the  urethra  is  nearer  the  upper  than  the  lower  part  of  the  corpus 
spongiosum,  but  it  soon  gains,  and  continues  to  occupy  the  middle  of 
that  body. 

Structure. — This  is  essentially  the  same  as  that  of  the  corpora 
cavernosa,  only  more  delicate.  Like  the  corpora  cavernosa,  it  is  dis- 
tended with  blood  during  erection;  but  never  acquires  the  same 
hardness.  The  outer  fibrous  tunic  is  much  thinner  ; the  trabeculae  of 
the  spongy  tissue  are  finer  and  more  equal  in  size,  and  the  veins  form 
a nearly  uniform  plexus  between  them  ; in  the  glans  the  meshes  of  this 
plexus  are  smallest  and  most  uniform.  The  helicine  arteries  are  also 
found  in  the  spongy  body,  excepting  in  the  part  which  forms  the  glans 
penis.  A considerable  artery,  derived  from  the  internal  pudic  (p.  615), 
enters  the  bulb  on  each  side,  and  supplies  the  greater  part  of  the 
spongy  body,  sending  branches  as  far  as  the  glans  penis,  which,  how- 
ever, is  chiefly  supplied  by  the  arteria  dorsalis.  Besides  these,  Kobelt 
describes,  as  constantly  present,  another  but  much  smaller  branch  of 
the  pudic  artery,  which,  he  says,  enters  the  bulb  on  the  upper  surface, 
about  an  inch  from  its  posterior  extremity,  and  runs  forwards  in  the 
corpus  spongiosum  to  the  glans.  Veins  issue  from  the  glans  and  ad- 
joining part  of  the  spongy  body,  to  end  in  the  vena  dorsalis  penis; 
those  of  the  rest  of  the  spongy  body  for  the  most  part  pass  out  back- 
wards through  the  bulb,  and  end  in  the  prostatic  and  pudic  venous 
plexuses:  some  emerge  from  beneath  the  corpora  cavernosa,  anasto- 

45* 


534 


URKTHRA  OF  THE  MALE. 


mose  with  their  veins,  and  end  partly  in  the  cutaneous  venous  system 
of  the  penis  and  scrotum,  and  partly  in  the  pudic  and  obturator  veins. 

The  lymphatics  of  the  penis  form  a dense  network  on  the  skin  of  the 
glans  and  prepuce,  and  also  underneath  the  mucous  lining  of  the 
urethra.  They  terminate  chietly  in  the  inguinal  glands.  Deep-seated 
lymphatics  are  also  described  as  issuing  from  the  cavernous  and 
spongy  bodies  and  passing  under  the  arch  of  the  pubes,  with  the  deep 
veins,  to  join  the  lymphatic  plexuses  in  the  pelvis. 

The  nerves  of  the  penis  are  derived  from  the  pudic  and  from  the 
hypogastric  plexus  of  the  sympathetic ; they  are  described  at  pp.  331 
and  354. 


URETHRA  OF  THE  MALE. 

The  male  urethra  extends  from  the  neck  of  the  bladder  to  the 
extremity  of  the  penis.  Its  total  length  has  been  very  differently 
stated  by  anatomists,  and,  indeed,  varies  much  according  to  the 
length  of  the  penis,  and  the  condition  of  that  organ.  An  examination 
of  a great  number  of  cases  gave  as  the  greatest  length  inches,  and 
the  least  7|.*  Its  diameter  varies  at  different  parts  of  its  extent,  as 
will  be  stated  more  particularly  in  detail.  The  tube  itself  consists 
essentially  of  a continuous  mucous  membrane,  supported  by  an  outer 
layer  of  submucous  tissue  connecting  it  with  the  several  parts  through 
which  it  passes.  In  accordance  with  the  name  or  character  of  those 
parts,  three  divisions  of  the  urethra  are  separately  described  as  the 
prostatic,  membranous,  and  spongy  portions. 

1.  The  first,  or  prostatic  portion,  is  the  part  which  passes  through 
the  prostate  gland.  It  is  from  12  to  15  lines  in  length,  is  the  widest 
part  of  the  canal,  and  is  larger  in  the  middle  than  at  either  end : at 
the  neck  of  the  bladder  its  diameter  is  nearly  4 lines,  then  it  widens  a 
little,  so  as  to  be  rather  more  than  4 lines,  and  in  old  persons  5 or  0, 
after  which  it  diminishes  like  a funnel,  until,  at  its  anterior  extremity, 
it  is  smaller  than  at  its  commencement.  It  passes  through  the  upper 
part  of  the  prostate,  above  the  middle  lobe,  so  that  there  is  more  of 
the  gland  below  it  than  above.  Though  enclosed  in  the  firm  glandular 
substance,  it  is  more  dilatable  than  any  other  part  of  the  urethra;  but 
at  its  upper  part,  immediately  at  the  neck  of  the  bladder,  it  is,  as  else- 
where stated,  much  more  resistant.  The  transverse  section  of  the 
urethra,  as  it  lies  in  the  prostate,  is  triangular,  the  apex  being  turned 
downwards. 

The  lining  membrane  of  the  prostatic  portion  of  the  urethra  is 
thrown  into  longitudinal  folds,  when  no  fluid  is  passing  along  it;  it 
forms  no  proper  valve  at  the  neck  of  the  bladder,  but  the  elevation 
named  the  uvula  vesica;  is  sometimes  seen  there.  Somewhat  in 
advance  of  this,  and  along  the  floor  of  the  passage,  projects  a narrow 
median  ridge,  about  8 or  9 lines  in  length,  and  Ih  line  at  its  greatest 
height:  this  ridge  gradually  rises  into  a peak  and  sinks  down  again  at 
its  anterior  or  lower  end,  and  is  formed  by  an  elevation  of  the  mucous 
membrane  and  subjacent  tissue.  This  is  the  crest  of  the  urethra 


* Whately  on  Strictures. 


THE  URETHRA. 


535 


(crista  urethrae),  more  generally  called  caput  gallinaginis  and  veru- 
monlanum.  On  each  side  of  this  ridge  the  surface  is  slightly  depressed, 
so  as  to  form  a longitudinal  groove,  named  the  prostatic  sinus,  the 
floor  of  which  is  pierced  by  numerous  foramina,  the  orifices  of  the 
prostatic  ducts.  Through  these  a viscid  fluid  oozes  on  pressure;  the 
ducts  of  the  middle  lobe  open  behind  the  urethral  crest,  and  some 
others  open  before  it. 

At  the  fore  part  of  the  most  elevated  portion  of  the  crest,  and 
exactly  in  the  middle  line,  is  a recess  usually  named  the  sinus  pocu- 
laris,  upon  or  within  the  margins  of  which  are  placed  the  slit-like 
openings  of  the  common  seminal,  or  ejaculatory  ducts,  one  at  each 
side.  This  median  depression  was  described  by  Morgagni,  who 
found  it  distinctly  present  in  twelve  out  of  fifteen  cases;*  and  it  has 
been  generally  noticed  by  anatomists  and  surgical  writers  since  his 
time,  but  it  has  lately  attracted  renewed  attention,  as  being  the 
probable  analogue  of  the  uterus  in  the  other  sex.  With  this  view  it 
has  been  examined  by  Weber,  and  named  by  him  vesica  prostaiica 
by  Huschke  it  is  more  appropriately  designated  the  utricle  (utriculus).j 
It  forms  a cul-de-sac  running  upwards  or  backwards,  from  three  to 
five  lines  deep,  and  usually  about  one  line  wide  at  its  entrance  and  for 
some  distance  up,  but  acquiring  a width  of  at  least  two  lines  at  its 
upper  end  or  fundus.  The  prominent  walls  of  the  narrow  portion 
form  the  urethral  crest,  and  its  fundus  appears  to  lie  behind  and 
beneath  the  middle  lobe,  and  between  the  two  lateral  lobes  of  the 
prostate.  Its  parietes,  which  are  distinct,  and  tolerably  thick,  are 
composed  of  fibrous  tissue  and  mucous  membrane,  and  inclose  on 
each  side  the  ejaculatory  duct ; numerous  small  glands  open  on  its 
inner  surface.  According  to  Kobelt  and  others,  the  caput  gallinaginis 
contains  some  well-marked  erectile  tissue,  and  it  has  been  supposed 
that  this  eminence  when  distended  with  blood,  may  offer  an  obstacle 
to  the  passage  of  the  semen  backwards  into  the  bladder. 

2.  The  membranous  portion  of  the  urethra  (fig.  478,  c),  comprises 
the  part  between  the  apex  ,of  the  prostate,  and  the  bulb  of  the  corpus 
spongiosum.  It  measures  three  quarters  of  an  inch  or  an  inch  along 
its  upper,  but  only  about  half  an  inch  on  its  lower  surface,  in  conse- 
quence of  the  projection  backwards  of  the  bulb  beneath  it.  This  is 
the  narrowest  division  of  the  urethra.  It  is  placed  beneath  the  pubic 
arch,  the  upper  concave  surface  being  distant  nearly  an  inch  from  the 
bone,  leaving  an  interval,  occupied  by  the  dorsal  vessels  and  nerves 
of  the  penis,  by  cellular  tissue,  and  some  muscular  fibres.  Its  lower 
convex  surface  is  turned  towards  the  perineum,  opposite  to  the  point 
of  meeting  of  the  transverse  muscles:  it  is  separated  by  an  interval 
from  the  last  part  of  the  rectum.  About  a line  in  front  of  the  prostate, 
at  a distance  of  nearly  an  inch  below  the  pubic  arch,  the  membranous 
part  of  the  urethra  passes  through  the  posterior  layer  of  the  triangular 
ligament  of  the  urethra,  and  is  then  placed  between  that  and  the 

* Adversaria  Anat.  iv.  animad.  3,  p.  6. 

t E.  H.  Weber,  Zusatze  zur  Lehre  vom  Baue  und  Verrichtungen  der  Geschlechts- 
Organe,  1846.' 

t Scemrnerring’s  Anatomie,  vol.  v. 


536 


THE  URETHRA. 


anterior  layer,  through  which  it  passes  some  way  further  forwards, 
but  both  of  these  fibrous  membranes  are  prolonged  upon  the  canal,  the 
one  backwards  and  the  other  forwards.  Between  these  two  layers 
the  urethra  is  surrounded  by  a little  erectile  tissue,  by  some  veins,  and 
also  by  the  fibres  of  the  compi-essor  urethrce  muscle:  beneath  it,  on 
each  side,  are  Cowper’s  glands.  This  portion  of  the  urethra  is  more 
forcibly  acted  on  by  muscular  structure,  in  consequence  of  the  sur- 
rounding muscular  fibres  immediately  investing  its  outer  surface. 

3.  The  spongy  portion  of  the  urethra,  by  far  the  longest  and  most 
variable  in  length  and  direction,  includes  the  remainder  of  the  canal, 
or  that  part  which  is  surrounded  by  the  erectile  tissue  of  the  corpus 
spongiosum.  Continuing  from  the  membranous  part,  it  ascends  at 
first  in  front  of  the  symphysis  pubis,  and  then  bends  downwards  and 
descends  to  the  extremity  of  the  penis.  Its  length  is  about  six  inches  ; 
and  its  form  and  diameter  vary  at  different  parts.  Thus  the  part 
contained  within  the  bulb,  sometimes  distinguished  as  the  bulbous 
portion,  is  somewhat  dilated,  especially  on  its  floor.  The  succeeding 
portion,  as  far  as  the  glans,  is  of  uniform  size,  being  intermediate  in 
this  respect  between  the  bulbous  and  membranous  portions,  and 
averaging  three  lines  or  upwards.  Seen  upon  a cross  section  it 
appears  like  a transverse  opening.  The  part  situated  in  the  glans 
has,  on  the  contrary,  a vertical  direction  on  a section,  and  is  again 
considerably  dilated,  forming  what  is  named  the  fossa  navicularis, 
which  is  about  four  or  six  lines  in  length,  and  is  most  evident  in  form 
of  a depression  on  the  floor  of  the  urethra. 

Lastly,  at  its  orifice,  which  is  a vertical  fissure  about  two  and  a 
half  to  three  lines  in  extent,  and  bounded  by  two  small  lips,  the 
urethra  is  again  contracted  and  reaches  its  narrowest  dimensions. 
In  consequence  of  its  form,  and  also  of  the  resistant  nature  of  the 
tissues  at  its  margin,  this  opening  does  not  admit  so  large  an  instru- 
ment as  even  the  membranous  portion  of  the  canal. 

General  direction  of  Urethra. — Considered  as  a whole  in  the  flaccid 
condition  of  the  penis,  the  urethra  describes  two  curves,  so  as  some- 
what to  resemble  an  italic  S;  the  prostatic  portion  runs  downwards 
and  fopwards, — the  membranous  portion  curves  upwards,  diverging 
from  the  rectum  at  a considerable  angle, — the  bulbous  portion  con- 
tinues to  ascend,  and  lastly,  having  bent  down  again  in  front  of  the 
pubes,  the  remainder  of  the  spongy  portion  descends.  When  the 
penis  is  in  a state  of  erection,  the  urethra  describes  only  a single 
curve,  having  its  concavity  turned  upwards.  From  the  details  already 
given,  it  will  further  be  seen  that  there  are  three  dilatations  along  the 
course  of  the  urethra;  viz.,  the  prostatic  sinus,  the  bulbous  sinus,  and 
the  fossa  navicularis. 

Mucous  Membrane. — The  lining  membrane  of  the  urethra,  which 
forms  a part  of  the  genito-urinary  mucous  membrane,  is  continuous, 
on  the  one  liand  with  that  of  the  bladder,  ureters,  and  kidneys,  and  on 
the  other  with  the  integument  of  the  glans  penis;  it  is  also  prolonged, 
as  it  were,  throughout  the  whole  length  of  the  seminal,  prostatic,  and 
other  ducts.  It  is  whitish  opposite  the  prostate,  but  redder  further 
down;  in  the  varial)le  parts  of  the  uretliral  canal  it  is  thrown  into 


THE  MUSCLES  OF  THE  PENIS. 


537 


longltudinalifolds,  which  disappear  during  the  state  of  distension.  The 
seminal  and  prostatic  ducts  open  into  the  prostatic  portion.  In  the 
bulbous  portion,  near  its  anterior  end,  are  the  two  openings  of  the 
ducts  of  Cowper's  glands. 

These  little  glands  themselves  (fig.  478,  /I)  are  seated  further  back 
than  the  bulb,  beneath  the  fore  part  of  the  membranous  portion  of  the 
urethra,  between  the  tw'O  layers  of  the  triangular  ligament,  the  ante- 
rior layer  supporting  them  against  the  urethra.  The  arteries  of  the 
bulb  pass  above,  and  the  transverse  fibres  of  the  compressor  urethrre 
beneath  these  glands.  They  are  two  small  firm  rounded  bodies,  about 
the  size  of  peas,  and  of  a deep  yellow  colour.  They  are  compound 
vesicular  or  racemose  glands,  composed  of  several  small  lobules  held 
together  by  a firm  investment.  The  branched  ducts,  which  commence 
in  cellular  crypts,  unite  to  form  a single  excretory  duct  for  each  gland, 
which  runs  forwards  with  its  fellow  for  about  an  inch  and  a half 
beneath  the  mucous  membrane,  and  the  two  terminate  in  the  floor  of 
the  bulbous  part  of  the  urethra  by  two  minute  orifices  opening  oblique- 
ly. These  glands  secrete  a viscid  fluid,  the  use  of  which  is  not 
known ; their  existence  is  said  not  to  be  constant,  and  they  appear  to 
diminish  in  old  age : sometimes  there  is  only  one  such  gland. 

Occasionally  a third  glandular  body  is  found  situated  in  front  of  and 
between  Cowper’s  glands;  this  has  been  named  the  anterior  prostate 
or  anti-prostatic  gland. 

The  whole  lining  of  the  urethra  is,  moreover,  beset  with  simple 
mucous  glands  and  follicles,  varying  much  in  size.  Besides  these, 
there  are  larger  recesses  or  lacunae,  opening  by  oblique  orifices  turned 
forwards  or  down  the  canal.  These  are  most  abundant  along  the 
floor  of  the  urethra,  especially  in  its  bulbous  part.  One  large  and  con- 
spicuous recess,  situated  on  the  upper  surface  of  the  fossa  navicularis, 
is  named  the  lacuna  magna. 

MUSCLES  OF  THE  PENIS  AND  URETHRA. 

Erector  penis,  or  ischio-cavernosus  (figs.  460,  507,  508,  c,  c ; fig. 
480,  d,  d).— This  muscle  embraces  the  unattached  surface  of  the 
crus  penis,  and  is  curved  to  correspond.  It  arises  behind  the  extre- 
mity of  the  crus  penis  from  the  tuber  ischii  (on  the  inner  aspect  of  the 
bone),  and  also  along  the  inner  and  the  outer  side  of  the  crus,  from 
the  corresponding  margins  of  the  ramus  of  the  pubes.  From  these 
points  of  origin  the  fleshy  fibres  are  directed  forward  to  a tendinous 
expansion,  which  is  spread  over  the  lower  surface  of  the  crus  penis  at 
its  fore  part. 

This  muscle  serves  to  compress  the  erectile  tissue,  with  which  its 
tendinous  fibres  are  connected,  and  thus  it  contributes  to  produce,  or  at 
least  maintain,  the  erection  of  the  penis.* 

* By  Krause  the  muscles  of  the  two  sides  have  been  described  as  in  some  cases  con- 
nected by  a thin  tendinous  expansion,  which,  according  to  that  anatomist,  extends  along 
the  outer  side  of  the  penis  over  the  dorsal  surface  of  the  organ,  and  at  the  same  time  over 
the  vessels  lying  upon  it  (Muller’s  Archiv.  1832),  but  this  connexion  between  the  muscles 
has  been  in  vain  sought  for  by  Theile  and  Kobelt  (Die  mannlichen  und  weiblichen  Wol- 
lust  Organe,  1844).  Mr.  Houston  has  also  described  (Dublin  Hosp.  Reports,  vol.  v.),  under 
the  name  of  compressores  vena  dorsalis  penis , two  slips  of  muscle,  separated  from  the  erec- 


53S 


MUSCLES  OF  THE  URETHRA. 


Accelerator  urincc — ejaculator  seminis,  or  bulbo  cavernosus  (figs. 
460,  507,  503,  h,  h;  fig.  480,  a,  a). — This  is  a single  muscle,  consist- 
ing of  two  s}mimetrical  parts,  which  together  surround  a portion  of 
erectile  structure  of  the  penis,  the  fibres  being  connected  at  both  ends. 

The  fleshy  fibres  of  the  muscle  take  origin  from  the  central  tendon  of 
the  perineum  (by  means  of  which  structure  the  accelerator  is  con- 
nected with  the  sphincter  ani,  together  with  the  two  transverse 
muscles),  and  from  the  median  tendinous  raphe  (e)  interposed  between 
the  two  halves  of  the  muscle.  The  larger  number  of  the  fibres  is 
directed  round  the  bulb  and  adjoining  part  of  the  corpus  spongiosum 
urethras,  and  those  from  opposite  sides  are  joined  above  that  body  by 
a strong  aponeurosis.  At  its  fore  part,  a portion  of  the  muscle  {b,  h) 
passes  over  the  sides  of  the  corpus  cavernosum,  to  the  dorsum  of  the 
penis,  to  be  inserted  into  a fascia,  which  covers  the  dorsal  vessels  of 
the  organ.  The  fibres  which  invest  the  posterior  and  most  prominent 
part  of  the  bulb  are  concealed,  more  or  less,  by  those  contiguous  to 
them  ; hence  they  have  been  described  as  constituting  a deep  layer  of 
the  muscle.  This  muscle  compresses  the  bulb  and  adjoining  part  of 
the  corpus  spongiosum  of  the  urethra  so  as  to  evacuate  fluid  lodged  in 
the  canal,  as  well  as  increase  the  turgescence  of  the  glans  during 
erection. 

The  transverse  muscle  of  the  perineum  (figs.  460,  507,  d,  d)  arises 
from  the  inner  surface  of  the  ascending  ramus  of  the  ischium,  and  is 
directed  transversely  or  obliquely  forwards  and  inwards  to  join  with 
the  muscle  of  the  opposite  side,  as  well  as  with  the  sphincter  ani  and 
accelerator  urinae  at  the  middle  of  the  perineum  ; the  several  muscles 
being  connected  by  fibrous  or  dense  cellular  tissue,  which  is  known  as 
the  central  tendon  of  the  perineum.  This  muscle  supports  the  peri- 
neum, and  is  accessory  to  the  levator  ani.  It  is  said  to  be  sometimes 
wantincr. 

O 

Besides  the  transverse  muscle,  one  or  more  small  slips  of  muscular  fibres  are 
occasionally  found  on  the  same  plane  with  it,  and  connected  at  one  end  like  that 
muscle  with  the  bone,  while  by  the  other  end  some  slips  are  joined  with  the 
fibres  of  the  accelerator  urinae  (or  constrictor  vaginae  in  the  female),  and  others 
with  the  external  sphincter  ani. 

Muscular  fibres  of  the  urethra. — With  the  membranous  portion  or 
isthmus  of  the  urethra  of  the  male  is  connected  a considerable  mass  of 
muscular  structure,  to  which  the  general  term  of  “ compressor  of  the 
canal”  is  applicable;  but  it  consists  of  parts  which  will  be  noticed 
separately.  The  whole  is  placed  between  the  layers  of  the  triangular 
ligament  or  the  deep  perineal  fascia,  with  the  arteries  of  the  bulb  and 
Cowper’s  glands. 

Compressor  urethrce  (new  muscles  of  the  membranous  part  of  the 
urethra,  Guthrie;  compressor  isthmi  urethra;,  constrictor  urethrae  mem- 
branaceae,  Muller). — This  muscle  consists  of  two  strata  (fig.  484, 

tores  penis  on  each  side  by  an  interval,  though  apparently  belonging  to  them.  They  are 
said  to  arise  from  the  rami  of  the  pubes,  above  the  origin  of  the  erector  muscles  and  crura 
of  the  penis,  and,  ascending  forwards,  are  inserted  above  the  dorsal  vein,  by  joining  each 
other  in  the  middle  line.  The  presence  of  such  muscular  slips  in  the  human  subject  must 
be  very  rare. 


MUSCLES  OF  THE  URETHRA. 


539 


one  of  which  passes  transversely 
above  the  urethra,  while  the  other  is 
beneath  the  canal.  The  two  layers 
are  fixed  together  to  the  ramus  of 
the  pubes  on  each  side  by  narrow 
ends ; in  the  middle  they  are  con- 
nected respectively  with  the  upper 
and  the  lower  surface  of  the  urethra, 
on  which  they  are  expanded  so  as 
to  cover  the  membranous  portion  of 
the  canal  in  its  whole  length.  In 
some  bodies  a tendinous  raphe, 
placed  over  the  middle  of  the  urinary 
canal,  separates  each  stratum  into 
lateral  halves;  in  such  cases  the 
fibres  may  be  said  to  arise  from  the 
bone  on  each  side,  and  to  be  inserted 
at  the  median  raphe,  where  those  of 
opposite  sides  join.  The  fibres  of 
the  lower  part  of  the  muscle  cover 
Cowper’s  glands. 

In  the  female,  the  compressor  ure- 
thr®  muscle  has  a precisely  similar 
arrangement. 


Fig.  484. 


Posterior  view  of  the  pubes,  with  part  of 
the  bladder  and  urethra  attached  (Santorini). 
— 1.  Body.  2.  Ramus  of  the  left  os  pubis. 
3.  Obturator  internus  muscle.  5.  Portion  of 
the  fundus  and  neck  laid  open,  showing  the 
orifices  of  the  ureters,  the  opening  leading 
into  the  urethra,  and  the  part  called  the 
trigone.  6.  The  prostate  gland.  7.  Trans- 
verse fibres  of  the  compressor  urethras  muscle, 
passing  above  the  urethra.  8.  Similar  fibres 
passing  beneath  that  canal. 


Circular  fibres,  Santorini  (stratum 

internum  circulare,  Muller). — A series  of  circular  muscular  fibres 
encircles  the  entire  of  the  membranous  part  of  the  urethra,  beneath 
the  transverse  muscle  just  described. 

Wilson's  muscles  (m.  pubo-urethrales). — By  this  name  are  known 
two  small  triangular  bundles  of  muscular  fibres  arising  each  by  a ten- 
don, which  “ is  affixed  to  the  back  part  of  the  symphysis  of  the  pubes, 
in  the  adult  about  an  eighth  of  an  inch  above  the  cartilaginous  arch  of 
the  pubes,  and  nearly  at  the  same  distance  below  the  attachment  of  the 
tendon  of  the  bladder.”*  The  tendons  give  rise  to  muscular  fibres, 
which  expand  as  they  descend,  and  are  connected  on  the  membranous 
part  of  the  urethra  with  the  muscular  structure  above  described,  one 
of  the  muscles  being  placed  at  each  side  of  the  urethra. 


The  transverse  compressor  of  the  urethra  was  known  to  Santorini.  One  of  the 
representations  of  it,  contained  in  his  posthumous  work,f  has  been  copied  for  the 
wood-cut.  Indistinctly  or  partially  noticed  by  other  anatomists,  the  muscle  was 
first  fully  described  by  Mr.  Guthrie  and  the  whole  of  the  muscular  structure  con- 

* A description  of  two  muscles  surrounding  the  membranous  part  of  the  urethra,  by 
James  Wilson,  in  Medico-Chirurg.  Trans,  vol.  i.  p.  176  (with  a plate).  London,  180P. 

As  regards  Wilson’s  muscles  : — Professor  Muller,  after  careful  examination  made  in  many 
bodies,  satisfied  himself  that  there  are  no  muscular  fibres  directed  downwards  from  the 
pubes  in  the  manner  assigned  to  these  muscles.  Mr.  Guthrie  arrived  at  the  same  conclu- 
sion. Still,  as  Wilson’s  statement  and  delineation  are  very  clear,  and  as  in  one  case  I 
myself  saw  a few  vertical  muscular  fibres  connected  with  the  transverse  compressor,  it  has 
been  thought  best  to  retain  the  muscles  in  the  text.  (R.  Q.) 

t Septemdecim  Tabulae. 

t The  Anatomy  and  Diseases  of  the  Neck  of  the  Bladder,  &c.,  1834. 


540 


COVERINGS  OF  THE  TESTES. 


nected  with  the  membranous  part  of  the  urethra  was  about  the  same  time  inves- 
tigated by  Professor  Miiller;  but  the  results  were  not  published  till  a later  period.* 

THE  TESTES  AND  THEIR  EXCRETORY  APPARATUS. 

The  testicles  or  testes,  the  two  glandular  organs  which  secrete  the 
seminal  fluid,  are  situated  in  the  scrotum,  each  being  suspended  by  its 
spermatic  cord. 

The  spermatic  cord. — The  parts  which  form  this  cord  are  the  ex- 
cretory duct  of  the  testicle,  named  the  vas  deferens,  the  spermatic 
artery  and  veins,  lymphatics,  nerves,  and  connecting  cellular  tissue. 
Besides  this,  both  the  cord  and  the  testis  have  several  coverings. 

The  spermatic  cord,  thus  composed,  extends  from  the  internal  abdo- 
minal ring  (vol.  i.  p.  303)  to  the  back  part  of  the  testicle.  Its  upper  por- 
tion lies  in  the  inguinal  canal,  an  oblique  passage  formed  in  the  lower 
part  of  the  abdominal  walls,  and  is  directed  downwards,  inwards,  and 
forwards  ; but,  on  escaping  from  that  canal  on  the  external  abdominal 
ring,  (vol.  i.  p.  415,)  it  descends  nearly  vertically  over  the  front  of  the 
pubes  into  the  scrotum.  The  construction  of  the  inguinal  canal,  the 
connexions  of  the  spermatic  cord  in  passing  through  it,  and  the  rela- 
tion of  both  to  inguinal  hernia,  will  be  considered  in  the  account  of  the 
“ inguinal  region.” 

O O 

COVERINGS  OF  THE  TESTIS  AND  CORD. 

Originally,  and  nearly  up  to  the  seventh  month  of  fcetal  life,  the 
testes,  with  their  ducts  and  vessels,  are  situated  at  the  back  part  of  the 
abdomen,  behind  the  peritoneum.  About  the  last-mentioned  period 
each  testicle  enters  the  corresponding  inguinal  canal,  and,  followed  by 
the  spermatic  cord,  passes  into  the  scrotum.  During  this  change  of 
position,  the  testis  and  cord  become  invested  with  certain  coverings, 
as  they  are  called,  derived  partly  from  the  serous,  muscular,  and 
fibrous  layers  of  the  abdominal  parietes,  and  partly  from  the  proper 
tissues  of  the  scrotum.  These  coverings,  as  found  in  the  adult,  and 
as  enumerated  from  without  inwards,  are,  after  the  sHn,  superficial 
fascia,  and  dartos  tissue  of  the  scrotum,  the  intercolumnar  fascia,  the 
cremaster  muscle  and  cremasteric  fascia,  and  the  inf undibuli form  fas- 
cia, which  is  united  to  the  cord  by  a layer  of  loose  cellular  tissue  ; 
lastly,  the  testicle  has  a special  serous  tunic,  named  the  tunica  vagi- 
nalis, which  forms  a closed  sac,  and  covers  the  proper  fibrous  coat  of 
the  gland. 

The  scrotum. — The  scrotum  forms  a purse-like  investment  for  the 
testes  and  part  of  the  spermatic  cords.  Its  condition  is  liable  to  cer- 
tain variations  according  to  the  state  of  the  health  and  other  circum- 
stances : thus,  it  is  short  and  corrugated  in  robust  persons  and  under 
the  effects  of  cold,  but  becomes  loose  and  pendulous  in  persons  of 
weak  constitution,  and  under  the  relaxing  influence  of  heat.  Its  sur- 
face is  marked  off  into  two  lateral  halves  by  a slight  median  ridge, 
named  the  raphe,  extending  forwards  to  the  under  side  of  the  penis, 
and  backwards  along  the  perineum  to  the  margin  of  the  anus. 

1.  The  skin  in  this  situation  is  very  thin,  and  is  of  a darker  colour 

* Ueber  die  organischen  Nervcn  der  ereclilen  mannliclien  Geschleclits-Organe,  &c.,  18.16. 


THE  DARTOS. 


541 


than  elsewhere  ; it  is  generally  thrown  into  rugae  or  folds,  which  are 
more  or  less  distinct  according  to  the  circumstances  already  men- 
tioned. It  is  furnished  with  sebaceous  follicles,  the  secretion  from 
which  has  a peculiar  odour,  and  it  is  covered  over  with  thinly  scat- 
tered crisp  and  flattened  hairs,  the  bulbs  of  which  are  seen  through  the 
skin  when  the  scrotum  is  extended.  The  superficial  blood-vessels  are 
also  readily  distinguished  through  this  thin  integument. 

2.  Immediately  beneath  the  skin  of  the  scrotum  (here  is  found  a thin 
layer  of  a peculiar  loose  reddish  tissue,  endowed  with  contractility, 
and  named  the  dartos.  This  subcutaneous  layer  is  continuous  with 
the  superficial  fascia  of  the  groin,  perineum,  and  inner  side  of  the 
thighs,  but  acquires  a different  structure,  and  is  perfectly  free  from 
fat.  This  dartoid  tissue  is  more  abundant  on  the  fore  part  of  the 
scrotum  than  behind,  and,  moreover,  it  forms  two  distinct  sacs,  which 
contain  the  corresponding  testes,  and  are  united  together  along  the 
middle  line  so  as  to  establish  a median  partition  between  the  two 
glands,  named  the  septum  scroti,  which  is  adherent  below  to  the  deep 
surface  of  the  raphe  and  reaches  upwards  to  the  root  of  the  penis. 
The  dartos  is  very  vascular,  and  consists  of  a loose  areolar  tissue 
containing  reddish  fasciculi,  which  have  long  been  recognised  as  pos- 
sessing peculiar  physiological  characters.  The  microscopical  and 
chemical  examination  of  the  dartos  did  not,  however,  appear  to  justify 
the  opinion  that  it  contained  muscular  tissue,  and,  accordingly  the 
slow  contractions  of  the  dartos  were  held  to  afford  an  example  of 
non-muscular  contractility ; but,  more  recently,  distinct  muscular 
fibres,  of  the  plain  or  unstriped  variety,  have  been  recognised  in  it 
(vol.  i.  p.  322).  Its  contractility,  as  just  stated,  is  slow  in  its  action ; it 
is  excited  by  the  application  of  cold  and  of  mechanical  stimuli,  but, 
apparently,  not  by  electricity.  By  its  action  the  testes  are  drawn  up 
or  sustained,  and  at  the  same  time  the  skin  of  the  scrotum  is  more  or 
less  corrugated. 

The  five  succeeding  layers  or  coverings  are  those  which  are  derived 
from  the  parietes  and  lining  membranes  of  the  abdomen. 

3.  fl'he  intercolumnar  or  spermatic  fascia  is  derived  from  the  tendon 
of  the  external  oblique  muscle  of  the  abdomen.  On  passing  forward 
through  the  opening  in  that  tendon,  named  the  external  abdominal 
ring,  the  spermatic  cord  receives  a tbin  membranous  investment, 
which  is,  as  it  were,  continuous  with  the  layer  of  so-called  interco- 
lumnar fibres  passing  obliquely  across  the  upper  border  of  that  open- 
ing. This  is  the  intercolumnar  fascia.  It  is  attached  above  to  the 
margins  of  the  external  ring,  and  is  prolonged  dowmwards  upon  the 
cord  and  testicle.  It  lies  at  first  beneath  the  superficial  fascia,  but 
lower  down  beneath  the  dartos,  and  it  is  intimately  connected  with 
the  layer  next  in  order. 

4.  The  succeeding  layer  is  composed  of  scattered  bundles  of  mus- 
cular tissue,  connected  together  into  a continuous  covering  by  inter- 
mediate cellular  membrane.  The  red  muscular  portion,  which  is 
continuous  with  the  lower  border  of  the  internal  oblique  muscle  of  the 
abdomen,  constitutes  the  cremaster  muscle,  or  tunica  erythroides,  and 
the  entire  covering  is  named  the  cremasteric  fascia. 

VOL.  II.  46 


542 


THE  CREMASTER  MUSCLE. 


The  cremaster  muscle,  so  named  because  it  serves  to  suspend  the 
testicle  (xp£|xaw,  to  suspend),  commences  within  the  inguinal  canal,  im- 
mediately beneath  the  lower  border  of  the  internal  oblique  muscle,  in 
the  form  of  two  bundles  of  muscular  tissue,  which  cross  obliquely  over 
the  front  of  the  spermatic  cord  ; lower  down,  the  muscular  fasciculi 
form  a series  of  loops  or  slings  with  their  concavities  turned  upwards, 
which  descend  upon  the  front  and  sides  of  the  cord,  and  which,  be- 
coming in  succession  longer  and  longer,  ultimately  reach  as  low  as 
the  testicle.  The  scattered  bundles  of  the  cremaster  muscle  would 
seem  to  be  derived  from  the  internal  oblique  muscle,  and  sometimes, 
perhaps,  from  the  transversalis  also.  The  lowermost  fibres  of  one  or 
both  muscles  may  be  supposed  to  be  carried  forward  by  the  testicle  in 
its  descent  into  the  scrotum.  The  attachments  of  the  cremaster  cer- 
tainly coincide  with  this  idea  of  its  formation.  When  carefully  ex- 
amined it  is  found  to  consist  of  an  external  and  an  internal  portion, 
the  separate  bundles  of  which  join  to  form  the  loops  upon  the  sper- 
matic cord  already  spoken  of.  The  external  and  larger  portion  arises 
from  the  deep  surface  of  Poupart’s  ligament,  or  rather  from  the  outer 
end  of  the  deep  crural  arch,  immediately  below  the  internal  oblique 
muscle,  and  passing  along  the  spermatic  cord,  through  the  external 
abdominal  ring,  descends  upon  it,  rather  on  its  outer  side,  and  spreads 
out  into  bundles,  differing  in  thickness  and  length  in  different  subjects. 
The  shorter  bundles  cross  in  loops  over  the  cord,  while  the  longest 
reach  down  towards  the  testicle,  and  are  attached,  directly  or  by 
means  of  tendinous  fibres,  to  the  outer  surface  of  the  tunica  vaginalis. 
Most  of  the  bundles  then  appear  to  be  prolonged  upwards  on  the  inner 
side  of  the  cord,  to  form  the  internal  and  smaller  portion  of  the  mus- 
cle, which  enters  the  lower  end  of  the  inguinal  canal,  and  is  inserted 
by  a small  tendinous  band  into  the  spine  and  crest  of  the  pubes,  close 
to  the  insertion  of  the  internal  oblique  muscle. 

Sometimes  the  loops  of  the  cremaster  completely  surround  the  cord, 
some  lying  behind  it,  but  the  larger  number,  being,  as  usual,  in  front. 
In  these  cases  it  would  seem  as  if  the  testicles  had  passed  through  the 
fibres  of  the  internal  oblique,  and  not  merely  beneath  them.  Occa- 
sionally the  muscular  bundles  can  be  traced  only  part  of  the  way 
down  the  cord,  the  lower  portion  of  the  latter,  as  well  as  the  testicle, 
being  covered  instead  by  a layer  of  firm  cellular  membrane,  similar  in 
appearance  to  that  which  connects  the  separate  muscular  bundles  to- 
gether, and  containing  some  tendinous  fibres. 

The  cremaster  muscles  not  only  aid  in  suspending  the  testes,  but 
can  raise  them  up  towards  the  ring,  and,  perhaps  at  the  same  time, 
compress  them  in  a slight  degree.  They  are  muscles  with  striped 
fibres,  and  in  some  persons  are  completely  under  voluntary  command. 
Their  action  is  sudden,  and  altogether  distinct  from  that  of  the  dartos. 

In  cases  of  old  scrotal  hernia,  and  also  in  hydrocele,  the  cremaster 
becomes  very  strongly  developed.  There  is,  of  course,  no  such 
muscle  in  the  female;  but  in  that  sex,  an  accidental  muscle,  analogous 
to  it,  may  be  produced  upon  an  inguinal  hernia  in  its  descent  beneath 
the  margin  of  the  internal  oblique  muscle. 

5.  The  infundibuliform  fascia  and  cellular  investment  oi  the  cord. — 


THE  FASCIA  PROPRIA. 


543 


These  are  continuous  above  vi’ith  the  fascia  tr an sver sails  and  the  sub- 
peritoneal  cellular  membrane.  Immediately  beneath  the  cremaster 
muscle  and  cremasteric  fascia,  and  closely  adherent  to  them,  is  a 
thin  membranous  layer,  which  loosely  surrounds  the  spermatic  cord. 
It  may  be  traced  above,  commencing  at  tbe  internal  abdominal  ring, 
in  form  of  a funnel-shaped  offset  from  the  transversalis  fascia,  and  is 
prolonged  as  a sheath  upon  the  vas  deferens  and  spermatic  vessels,  as 
these  pass  out  of  the  abdomen.  It  then  descends  through  the  inguinal 
canal  and  scrotu.m  upon  the  cord,  investing  it  completely,  and  being 
connected  below  with  the  posterior  part  of  the  testicle  and  the  outer 
surface  of  its  serous  tunic. 

On  forcing  air  beneath  the  infundibuliform  fascia,  a quantity  of 
loose  and  delicate  cellular  tissue  is  seen  to  connect  its  internal  or  deep 
surface  with  the  vas  deferens  and  spermatic  blood-vessels,  and  to  form 
lamellge  between  them.  This  areolar  tissue  is  continuous  above  with 
the  sub-serous  cellular  tissue  found  beneath  the  peritoneum  on  the 
anterior  wall  of  the  abdomen ; below,  it  is  lost  upon  the  back  of  the 
testicle.  Together  with  the  infundibuliform  fascia  just  described,  it 
forms  \he  fascia  propria  of  Sir  A.  Cooper. 

Lying  amongst  this  loose  cellular  tissue,  in  front  of  the  upper  end  of 
the  cord,  there  is  often  seen  a fibro-cellular  band,  which  is  connected 
above  with  the  pouch  of  peritoneum  found  opposite  the  upper  end  of 
the  inguinal  canal,  and  reaches  downwards  for  a longer  or  shorter 
distance  along  the  spermatic  cord.  Occasionally  it  may  be  followed 
as  a fine  cord,  down  to  the  upper  end  of  the  tunica  vaginalis ; some- 
times no  trace  of  it  whatever  can  be  detected.  It  is  the  vestige  of  a 
tubular  process  of  the  peritoneum,  which  once  connected  the  tunica 
vaginalis  with  the  general  peritoneal  membrane.  The  testes  of  the 
foetus  are  placed  in  the  abdomen  behind  the  peritoneum.  When  they 
are  about  to  escape  from  the  abdominal  cavity,  a pouch  of  the  lining 
membrane  extends  itself  in  advance  of  each  testicle  along  the  corre- 
sponding inguinal  canal  towards  the  scrotum.  Into  this  pouch,  or 
processus  vaginalis  peritoncni,  as  it  is  named,  the  testicle  projects  from 
behind,  supported  by  a duplicature  of  the  serous  membrane,  named 
the  mesorchium.  Sooner  or  later  after  the  gland  has  reached  the 
scrotum  the  upper  part  or  neck  of  this  pouch  becomes  obliterated,  from 
the  internal  abdominal  ring  near  to  the  upper  part  of  the  testicle,  leaving 
no  trace  but  the  indistinct  fibrous  cord  already  described,  whilst  the 
lower  part  remains  as  a closed  serous  sac,  into  which  the  testicle 
depends,  and  which  is  henceforth  named  the  tunica  vaginalis.  Some- 
times the  tube  of  peritoneum  becomes  closed  at  intervals  only,  leaving 
a series  of  sacculi  along  the  front  of  the  cord  ; or  a long  pouch  may 
continue  open  at  the  upper  end,  leading  from  the  abdominal  cavity 
into  the  inguinal  canal.  Lastly,  in  some  instances,  the  peritoneal 
process  remains  altogether  pervious,  and  the  cavity  of  the  tunica 
vaginalis  is  continuous  with  that  of  the  peritoneum.  In  such  a case 
of  congenital  defect,  a portion  of  intestine  or  omentum  may  descend 
from  the  abdomen  into  the  inguinal  canal  and  scrotum,  and  constitute 
what  is  named  a congenital  hernia. 

In  the  female,  an  analogous  pouch  of  peritoneum  descends  in  the 


544 


COVERINGS  OF  THE  TESTIS. 


Fig.  485. 


foetus,  for  a short  distance  along  the  round  ligament  of  the  uterus,  and 
has  received  the  appellation  of  the  canal  of  Nuck.  Traces  of  it  may 
almost  always  be  seen  in  the  adult. 

6.  The  tunica  vaginalis. — Beneath  the  parts  already  described, 
which  form  investments  common  to  the  cord  and  testis,  is  the  proper 
serous  covering  of  the  latter,  named  the  tunica  vaginalis.  The  mode 
in  which  this  coat  is  derived  from  the  peritoneum  has  just  been 
explained.  In  its  completed  condition  it  forms  a shut  sac,  the  opposite 
walls  of  which  are  in  contact  with  each  other.  Like  the  serous  mem- 
branes in  general,  of  which  it  affords  one  of  the  simplest  examples,  it 
may  be  described  as  consisting  of  a visceral  and  a parietal  portion. 
The  former  closely  invests  the  greater  part  of  the  body  of  the  testis 
(fig.  485,-),  as  well  as  the  epididymis  ■*),  between  which  parts  it 
recedes  in  form  of  a pouch,  and  lines  their  con- 
tiguous surfaces,  and  it  adheres  intimately  to 
the  proper  fibrous  tunic  of  the  gland  ; hence  it 
is  named  tunica  vaginalis  testis.  Along  the 
posterior  border  of  the  gland,  where  the  vessels 
and  ducts  enter  or  pass  out,  the  serous  coat  is 
wanting,  being  refiected  thence  so  as  to  become 
continuous  with  the  parietal  or  scrotal  portion 
(®),  which  completes  the  sac,  and  forms  a smooth 
lining  membrane  to  the  lower  part  of  the  other 
investments  of  the  testicle,  viz.,  the  infundibuli- 
form  fascia,  the  cremaster,  and  the  spermatic 
fascia,  which  are  there  blended  together  and 
connected  with  the  external  surface  of  the  tunica 
vaginalis. 

The  parietal  or  scrotal  portion  of  the  tunica 
vaginalis  is  more  extensive  than  that  which 
covers  the  body  of  the  testis ; it  reaches  up- 
The  testicle  and  part  of  Wards,  sometimes  for  a considerable  distance, 

the  spermatic  cord,  with  the  upon  the  Spermatic  cord,  extending  somewhat 
tunica  vaginalis  laid  open. — i ! i ,i  • T • i t. 

1.  Lower  part  of  the  sper-  higher  on  the  inner  than  on  the  outer  side.  It 

matic  cord.  2.  Body  of  the  also  reaches  downwards  below  the  testicle, 

tesiicle.  3,  4.  The  epidi-  i*i*Lr  jj* 

dymis.  3,  Globus  major  or  which,  therefore,  appears  to  be  suspended  at 

head.  4.  Globus  minor  or  the  back  of  the  serous  sac,  when  this  latter  is 
tail.  5.  Internal  surface  of 


scrotal  portion  of  tunica 
vaginalis. 


distended  with  fluid. 


The  internal  surface  of  the  tunica  vaginalis  is 
free,  smooth,  epitheliated,  and  moistened  with 
a small  quantity  of  an  albuminous  fluid.  The  epithelium  is  squamous. 

VESSELS  AND  NERVES  OF  THE  COVERINGS  OF  THE  TESTIS 

AND  CORD. 


The  arteries  are  derived  from  several  sources.  Thus,  the  two  ex- 
ternal pudic  arteries  (vol.  i.  p.  623),  branches  of  the  femoral,  reach  the 
front  and  sides  of  the  scrotum,  supplying  the  integument  and  dartos; 
the  superficial  perineal  branch  of  the  internal  pudic  artery  (p.  615)  is 
distributed  to  the  back  part  of  the  scrotum  ; and,  lastly,  more  deeply 
seated  than  either  of  these,  is  a branch  given  from  the  epigastric 


THE  TESTES. 


515 


artery,  named  cremasteric  (p.  620),  because  it  is  chiefly  distributed 
to  the  cremaster  muscle,  but  it  also  supplies  small  branches  to  the 
other  coverings  of  the  cord,  and  its  ultimate  divisions  anastomose  with 
those  of  the  other  vessels.  The  veins,  which,  owing  to  the  thinness  of 
the  integuments,  are  apparent  on  the  surface  of  the  scrotum,  follow 
the  course  of  the  arteries.  The  lymphatics  pass  into  the  inguinal  lym- 
phatic glands. 

The  nerves  also  proceed  from  various  sources.  Thus,  the  ilio- 
inguinal, a branch  of  the  lumbar  plexus  (vol.  ii.  p.  322),  comes  forwards 
through  the  external  abdominal  ring,  and  supplies  the  integuments  of 
the  scrotum ; this  nerve  is  joined  also  by  a filament  from  the  ilio-hypo- 
gastric  branch  of  the  same  plexus:  sometimes  two  separate  cutaneous 
nerves  come  forward  through  the  external  ring.  The  two  superficial 
perineal  branches  of  the  internal  pudic  nerve  (p.  331)  accompany  the 
artery  of  the  same  nerve  and  supply  the  inferior  and  lateral  parts  of 
the  scrotum.  The  inferior  pudendal,  a branch  of  the  small  sciatic 
nei’ve  (p.  332)  joins  with  the  perineal  nerves,  and  is  distributed  to  the 
sides  and  fore  part  of  the  scrotum.  Lastly,  a deeper  nerve,  springing 
from  the  lumbar  plexus,  and  named  genito-crural  (p.  323),  comes  into 
contact  with  the  spermatic  cord  at  the  internal  abdominal  ring,  passes 
with  it  through  the  inguinal  canal,  and  supplies  the  fibres  of  the  cre- 
master, besides  sending  a few  filaments  to  the  other  deep  coverings  of 
the  cord  and  testicle. 

THE  TESTES. 

The  testes  are  suspended  in  the  scrotum  at  unequal  heights,  that  of 
the  left  side  being  usually  lower  than  the  other.  They  are  of  an  oval 
form,  but  are  slightly  compressed  laterally,  so  that  they  have  two 
somewhat  flattened  sides  or  faces,  an  upper  and  a lower  end,  an  ante- 
rior and  a posterior  border.  They  are  from  an  inch  and  a half  to  two 
inches  long,  about  an  inch  and  a quarter  from  the  anterior  to  the 
posterior  border,  and  nearly  an  inch  from  side  to  side.  The  weight  of 
each  varies  from  three  quarters  of  an  ounce  to  an  ounce,  and  the  left 
is  often  a little  the  larger  of  the  two. 

Both  sides  of  the  testicle,  the  upper  and  the  lower  end,  and  the 
anterior  border,  which  is  rounded,  are  free,  smooth,  and  closely 
invested  by  the  tunica  vaginalis.  The  posterior  border,  however, 
which  is  also  called  the  straight  border,  is  attached  to  the  spermatic 
cord,  and  it  is  here  that  the  vessels  and  nerves  enter  or  pass  out. 
When  ihe  testis  is  suspended  in  its  usual  position,  its  upper  end  is 
directed  obliquely  forwards  and  outwards,  as  well  as  upwards,  whilst 
the  lower,  which  is  rather  smaller,  has  the  opposite  direction.  It 
follows  from  this  that  the  posterior  or  attached  border  is  turned  a little 
upwards,  and  the  outer  flattened  face  slightly  backwards. 

Along  the  outer  edge  of  the  posterior  border  of  the  gland,  and  rest- 
ing also  on  the  neighbouring  portion  of  its  outer  face,  is  placed  a long 
narrow  appendage,  named  from  its  position  the  epididymis  {M  and 
SlSufiog,  testis).  This  body  is  curved  so  as  to  be  adapted  to  the  testicle. 
Its  upper  extremity,  which  is  enlarged  and  obtuse,  is  named  the  head 
of  the  epididymis,  or  globus  major  Ij') ; the  lower,  which  is  more 

46* 


546 


THE  TESTES. 


pointed,  is  termed  the  tail,  or  globus  minor  (■*) ; whilst  the  intervening 
and  narrower  portion  is  named  the  body.  The  outer  convex  surface 
of  the  epididymis  and  the  thin  anterior  border  are  free,  and  covered 
by  the  tunica  vaginalis.  The  inner  surface,  except  at  the  upper  and 
lower  ends,  is  also  free,  and  invested  by  the  same  tunic,  w'hich  here 
forms  a pouch  between  the  epididymis  and  the  outer  face  of  the  testi- 
cle, and  nearly  surrounds  the  epididymis,  except  along  its  posterior 
border,  which  is  held  to  the  gland  by  a duplicature  of  the  serous  mem- 
brane. At  its  upper  and  lower  extremity  the  inner  surface  of  the 
epididymis  is  attached  to  the  testicle,  — the  lower  end,  or  globus 
minor,  by  fibrous  tissue  and  a reflection  of  the  tunica  vaginalis,  the 
globus  major  by  the  efferent  ducts  of  the  testicle  also.  Lastly,  the 
long  posterior  border  of  this  appendage  is  connected  with  the  sper- 
matic cord  by  numerous  blood-vessels,  supported  by  dense  cellular 
tissue. 

The  epididymis  contains  a part  of  the  excretory  apparatus  of  the 
testicle,  and  is  principally  composed  of  the  convolutions  of  a long  tor- 
tuous canal  or  efferent  duct,  which  will  be  presently  described. 

Upon  the  head  of  the  epididymis  there  is  very  commonly  found  a 
small  soft  pendulous  body  of  a reddish  colour,  about  two  or  three  lines 
in  length.  Its  presence  was  first  pointed  out  by  Morgagni,  but  its 
nature  is  not  known. 

Structure  of  the  testis. — Besides  the  numerous  coverings  already 
noticed,  the  testis  is  enclosed  in  a proper  coat,  named  the  tunica  albu- 
ginea (fig.  486,^).  This  is  a dense  unyielding  fibrous  membrane,  of  a 
bluish-white  colour,  and  about  half  a line  thick,  which  immediately 
invests  the  soft  substance  of  the  testicle,  and  preserves  the  form  of  the 
gland.  It  is  composed  of  bundles  of  fibrous  tissue,  which  interlace  in 
every  direction.  The  outer  surface  is  for  the  most  part  covered  by 
the  tunica  vaginalis,  except  along  the  posterior  border  of  the  testicle, 
where  the  spermatic  vessels  pass  through,  and  except  also  at  the  parts 
to  which  the  two  extremities  of  the  epididymis  are  attached.  From 
the  upper  end  of  the  testicle,  opposite  the  globus  major,  the  tunica 
albuginea  is  continuous  with  thin  prolongations  of  fibrous  tissue  which 
invest  the  epididymis,  support  and  hold  together  the  numerous  convo- 
lutions of  its  tortuous  canal,  and  are  ultimately  continued  upon  the  vas 
deferens. 

At  the  posterior  and  upper  border  of  the  testis,  the  fibrous  tissue  of 
the  tunica  albuginea  is  prolonged  forwards  for  a few  lines  into  the 
substance  of  the  gland,  so  as  to  form  within  it  an  incomplete  vertical 
septum,  known  as  the  corpus  Highmorianum,  and  named  by  Sir  A. 
Cooper  mediastinum  testis  (®).  Projecting  inwards  from  the  back  of 
the  testis,  it  extends  from  the  upper  nearly  to  the  lower  end  of  the 
gland,  and  it  is  wider  above  than  below.  The  firm  tissue  of  which  it 
is  composed  is  traversed  by  a network  of  seminal  ducts,  and  by  the 
larger  blood-vessels  of  the  gland,  which  are  lodged  in  channels  formed 
in  the  fibrous  tissue. 

From  the  front  and  sides  of  the  corpus  Highmorianum  numerous 
slender  fibrous  cords  of  various  lengths  are  given  off  in  all  directions, 
and  are  attached  by  their  other  ends  to  the  internal  surface  of  the 


THE  TESTES. 


547 


tunica  albuginea  at  different  points,  so  as  to  assist  in  maintaining  the 
general  shape  of  the  testicle.  Other  offsets  from  the  mediastinum, 
consisting  of  delicate  membranous  laminae,  meet  with  similar  ones 


[Fig.  486.  Fig.  487. 


Fig.  486.  A transverse  section  of  the  testicle.  1.  The  cavity  of  the  tunica  vaginalis.  2.  The 
tunica  albuginea  3.  Corpus  highmorianum  or  mediastinum  testis  4.  Tunica  vasculosa  of  the 
testis.  5.  Glandular  substance  of  the  testicle.  6.  A section  of  the  epididymis. 

Fig.  487.  A plan  of  a vertical  section  of  the  testicle,  to  show  the  mode  of  arrangement  of  the 
ducts.  1,  1.  Tunica  albuginea.  2,  2,  Corpus  highmorianum.  3,  3.  Tubuli  seminiferi  convoluted 
into  lobules.  4.  Vasa  recta.  5.  Rete  vasculosum  testis.  6.  Vasa  efferentia.  7.  Coni  vasculosi 
constituting  the  globus  major  of  the  epididymis.  8.  Body  of  the  epididymis.  9.  Its  globus  minor. 
10.  Vas  deferens.  11.  Vasculum  aberrans  or  blind  duct. — S.  & H.] 

from  the  tunica  albuginea,  and  enclose  tbe  several  lobes  into  which 
the  substance  of  the  testis  is  divided.  The  whole  internal  surface  of 
the  tunica  albuginea  is  covered  by  a multitude  of  fine  blood-vessels, 
which  are  branches  of  the  spermatic  artery  and  veins,  and  are  held 
together  by  a delicate  cellular  web.  Similar  delicate  ramifications 
of  vessels  are  seen  on  the  various  fibrous  offsets  of  the  mediastinum, 
upon  which  the  blood-vessels  are  thus  supported  in  the  interior  of  the 
gland.  This  vascular  network,  together  with  its  connecting  cellular 
tissue,  constitutes  the  tunica  vasculosa  {*)  of  Sir  A.  Cooper. 

The  proper  glandular  substance  of  the  testicle  (®)  is  a soft  pulpy 
mass  of  a reddish-yellow  colour,  which  is  divided  into  numerous  small 
lobes,  containpd  in  the  separate  compartments  formed  by  the  fibro- 
vascular  expansions  which  extend  between  the  corpus  Highmorianum 
and  the  internal  surface  of  the  tunica  albuginea  (see  the  illustrative 
plan,  fig.  487).  The  number  of  these  lobes  (lobuli  testis)  has  been  es- 
timated at  250  by  Berres,  and  upwards  of  400  by  Krause.  Their 
shape  is  somewhat  conical  or  pyriform,  the  larger  end  of  each  being 
turned  towards  the  surface  of  the  testicle,  and  the  smaller  one  towards 
the  mediastinum.  They  differ  in  size  according  to  their  position,  those 
which  occupy  the  middle  of  the  gland  and  reach  its  anterior  border 
being  longer  and  larger  than  the  rest.  The  substance  of  these  lobes 


548 


THE  TESTES. 


consists  almost  entirely  of  minute  convoluted  lubes  named  tubuli 
seminiferi,  vascula  serpentina,  in  the  interior  of  which  the  seminal 
fluid  is  secreted.  Each  lobe  contains  one,  two,  three,  or  even  more 
of  these  convoluted  tubules,  the  coils  of  which,  being  but  loosely  held 
together,  may  be  more  or  less  successfully  unravelled  by  careful  dis- 
section under  water.  According  to  Monro,  their  total  number  is 
about  300,  and  the  length  of  each  tubule  about  sixteen  feet ; but  Lauth 
estimates  their  mean  number  to  be  840,  and  the  average  length  of 
each  to  be  not  more  than  two  feet  and  a quarter.  Their  diameter, 
which  is  uniform  through  their  whole  course,  is  from  ^^^jth  to 
of  an  inch.  The  capillary  vessels  are  distributed  in  form  of  a net- 
work upon  the  outer  surface  of  the  tubules,  supplying  them  with  blood, 
and  constituting,  together  with  fine  bundles  of  cellular  tissue  in  very 
sparing  quantity,  a slender  bond  of  union  between  them ; this  feeble 
connexion  between  the  tubuli  renders  necessary  their  inclosure  and 
support  by  a dense  fibrous  capsule.  As  compared  with  the  ultimate 
ducts  of  glands  generally,  the  coats  of  the  tubuli  seminiferi  are  strong, 
and  hence,  notwithstanding  their  comparatively  loose  aggregation, 
they  may,  as  well  as  the  system  of  ducts  into  which  they  ultimately 
unite,  be  injected  with  mercury.  They  are  lined  with  an  epithelium, 
composed  of  nucleated  granular  corpuscles.  The  mode  in  w'hich  they 
commence,  as  far  as  at  present  known,  appears  to  be  twofold,  for  they 
have  been  seen  commencing  near  the  surface  of  the  lobes  by  free 
closed  extremities,  but  more  frequently  by  anastomotic  arches  or 
loops.  They  also  anastomose  together  occasionally  in  their  course, 
and  the  tubuli  of  adjacent  lobes  are  often  found  communicating  with 
one  another.  After  an  exceedingly  tortuous  or  serpentine  course  from 
side  to  side  of  the  lobe  to  which  they  belong,  they  at  length,  in  ap- 
proaching the  corpus  Highmorianum,  lose  in  a great  measure  the 
convoluted  disposition,  becoming  at  first  slightly  flexuous  and  then 
nearly  straight.  The  separate  tubuli  of  each  lobe,  and  then  those  of 
adjoining  lobes,  unite  together  into  larger  tubes,  which  pass  through  the 
fibrous  tissue  of  the  mediastinum  and  amongst  the  branches  of  the 
blood-vessels,  and  form  the  next  order  of  the  seminal  ducts. 

These,  which,  from  their  comparatively  straight  course,  are  named 
tubuli  recti  or  vasa  recta  (*),  are  upwards  of  twenty  in  number,  and 
are  fom  -g?0th  to  y^th  of  an  inch  in  diameter.  They  pass  upwards  and 
backwards  through  the  fibrous  tissue,  as  already  stated,  and  end  in  a 
close  network  of  tubes,  named  by  Haller  the  rete  vascuJosum  testis 
(figs.  487,®  488,^),  which  lies  in  the  substance  of  the  corpus  Highmo- 
rianum, along  the  back  part  of  the  testicle,  but  in  front  of  the  primary 
subdivisions  of  the  spermatic  blood-vessels  before  these  enter  the  gland. 
The  tubes  composing  the  rete  have  very  thin  walls. 

All  the  seminal  ducts  hitherto  mentioned,  namely,  the  tubuli  semini- 
feri, tubuli  recti,  and  rete  testis,  are  included  within  the  proper  fibrous 
coat  of  the  testicle,  and  form  in  great  part  the  substance  of  the  gland; 
but  the  succeeding  order  of  ducts  transmit  the  seminal  fluid  from  the 
testis  to  the  epididymis,  and  are  named  accordingly  vasa  efferentia 
(®).  These  are  from  twelve  to  fifteen,  or  sometimes  twenty  in  num- 
ber; they  pei  forate  the  tunica  albuginea  at  the  upper  end  of  the  pos- 


THE  VAS  DEFERENS. 


549 


terior  border  of  the  testicle,  opposite  to  the  globus  major  of  the 
epididymis,  of  which  they  may  be  said  to  form 
a part,  and  in  the  convoluted  canal  of  which 
they  ultimately  terminate.  On  emerging  from 
the  testis,  these  vasa  efferentia  are  straight, 
but,  becoming  more  and  more  convoluted,  as 
they  proceed  towards  the  epididymis,  they 
form  a series  of  small  conical  masses,  the 
bases  of  which  are  turned  in  the  same  direc- 
tion, and  which  are  named  coni  vascuhsi 
(fig.  487,^  fig.  488,®).  The  largest  of  these 
cones  is  about  eight  lines  long,  and,  when 
unrolled,  each  is  found  to  consist  of  a single 
coiled  duct,  varying  from  six  to  eight  inches 
in  length,  and  the  diameter  of  which  gra- 
dually decreases  from  the  testis  to  the  epi- 
didymis (Huschke).  Opposite  to  the  globus 
major  these  separate  efferent  vessels  open,  at 
intervals  of  about  three  inches,  into  a single 
canal  or  duct,  the  intervening  and  subsequent 
convolutions  of  which  constitute  the  epididy- 
mis itself.  , rr,  IK 

1 he  canal  of  the  epididymis  (hg.  487,s  nea,  2.  Seminiferous  tubes. 
488,n  is  disposed  in  innumerable  coils,  and  The  rete  vascuiosum  testis, 
extends  from  the  globus  major  downwards  to  has  ruptured  the  tubes.  5.  The 

the  globus  minor  or  tail,  where,  turning  up-  efferentia  whi^  form  the 
V . . . , I I com  vasculosi.  6.  Coni  vascii- 

wards,  it  is  continued  on  as  the  vas  deferens,  losi  forming  the  head  of  the 
Its  flexuosities  are  exceedingly  numerous,  so  epididymis.  7.  Epididymis.  8. 

^ I 11  1 • c 1 1 . Globus  minor  of  the  epididymis. 

that  when  unrolled  it  is  found  to  be  twenty  g.  Vas  deferens.— s.  & H.] 
feet  and  upwards  in  length.  The  smallest 

windings  are  supported  and  held  together  by  fine  cellular  tissue;  but, 
besides  this,  numerous  fibrous  partitions  are  interposed  between  larger 
masses  of  the  coils,  which  have  been  named  the  lobes  of  the  epidi- 
dymis, the  general  direction  of  which  is  across  that  body.  The  canal 
of  the  epididymis  is,  at  its  commencement,  about  of  an  inch  in 

diameter,  but  it  goes  on  diminishing,  till,  towards  the  globus  minor, 
it  is  about  ■g^'gth  of  an  inch,  after  which  it  again  increases  in  size,  and 
becomes  less  tortuous  as  it  approaches  the  vas  deferens.  Its  coats, 
which  are  at  first  very  thin,  become  thicker  as  it  proceeds. 

VAS  DEFERENS. 

The  vas  deferens,  or  excretory  duct  of  the  testis  (®),  is  a hard  round 
tube,  which  forms  the  continuation  upwards  of  the  convoluted  canal 
of  the  epididymis.  It  commences  at  the  lower  end  of  that  appendage, 
or  the  globus  minor,  and,  being  at  first  rather  tortuous,  but  afterwards 
becoming  straight,  it  ascends  upon  the  inner  side  of  the  epididymis, 
and  along  the  back  of  the  testicle,  separated  from  both,  however,  by 
the  blood-vessels  passing  to  or  from  the  gland.  Continuing,  then,  to 
ascend  in  the  spermatic  cord,  the  vas  deferens  accompanies  the  sper- 
matic artery,  veins,  and  nerves,  as  far  as  the  internal  abdominal  ring. 


[Fig.*488. 


The  testicle  injected  with 


550 


THE  VAS  DEFERENS. 


Between  the  testicle  and  the  external  ring  its  course  is  vertical ; it  lies 
behind  the  ^spermatic  vessels,  and  is  readily  distinguished  by  its  hard 
cord-like  leel.  Having  passed  obliquely  upwards  and  outwards  along 
the  inguiual  canal, and  reached  the  inner  border  of  the  internal  abdomi- 
nal ring,  it  leaves  the  spermatic  vessels  (which  extend  to  the  lumbar  re- 
gion), and  turns  suddenly  downwards  and  inwards  into  the  pelvis,  cross- 
ing over  the  external  iliac  vessels,  and  turning  round  the  outer  or  iliac 
side  of  the  epigastric  artery.  Running  beneath  the  peritoneum,  it 
reaches  the  side  of  the  bladder  (fig.  478,  ?),  on  which  it  curves  back- 
wards and  downwards  to  the  under  surface  of  that  viscus,  and  then 
runs  forwards  to  the  base  of  the  prostate  gland.  In  its  course  within 
the  pelvis,  the  vas  deferens  gradually  approaches  nearer  to  the  middle 
line  ; it  crosses  over  and  to  the  outer  side  of  the  cord  of  the  obliterated 
hypogastric  artery,  and  to  the  inner  side  of  the  ureter.  Beyond  this 
point,  where  the  vas  deferens  reaches  the  base  of  the  bladder,  it 
ceases  to  be  covered  by  the  peritoneum,  and  is  found  attached  to  the 
coats  of  the  bladder,  lying  between  that  viscus  and  the  rectum.  In 
this  situation  (fig.  479,^,®)  it  runs  forwards,  and  at  the  same  time 
inwards,  so  as  gradually  to  approach  its  fellow  of  the  opposite  side. 
Upon  the  base  of  the  bladder,  the  two  vasa  deferentia  are  situated 
between  two  membranous  receptacles  for  the  semen,  named  the  semi- 
nal vesicles  (®,  ; and  close  to  the  base  of  the  prostate  (®),  each  vas 

deferens  ends  by  joining  with  the  duct  from  the  corresponding  seminal 
vesicle,  which  is  placed  on  its  outer  side,  to  form  one  of  the  two  com- 
mon seminal  or  ejaculatory  ducts  (’'’). 

The  vas  deferens,  therefore,  pursues  a long  and  somewhat  compli- 
cated course,  from  its  commencement  at  the  lower  end  of  the  epididy- 
mis to  its  termination  at  the  base  of  the  prostate,  beneath  the  bladder. 
It  measures  nearly  two  feet  in  length.  In  the  greater  part  of  its  extent 
it  is  cylindrical  or  slightly  compressed,  and  has  an  average  diameter 
of  about  one  line  and  a quarter;  but  towards  its  termination,  beneath 
the  bladder,  it  becomes  enlarged  and  sacculated,  approaching  thus  in 
character  to  the  seminal  vesicle.  Previous  to  its  junction  with  the 
duct  of  that  vesicle,  it  again  becomes  narrowed  to  a fine  cylindrical 
canal.  The  walls  of  the  vas  deferens  are  very  dense  and  strong, 
measuring  one-third  of  a line  in  thickness;  whilst,  on  the  other  hand, 
the  canal  is  proportionably  fine,  its  area  being  only  from  one-fourth  to 
one-half  a line  across.  In  the  sacculated  portion  the  passage  is  much 
wider,  and  the  walls  are  thinner  in  proportion. 

Besides  an  external  cellular  investment,  and  an  internal  lining 
mucous  membrane,  the  vas  deferens  is  provided  with  an  intermediate 
tunic,  which  is  thick,  dense  in  structure,  somewhat  elastic,  and  of  a 
deep  yellowish  colour.  This  coat  consists  principally  of  longitudinal 
fibres,  mixed  with  some  circular  ones.  Huschke  describes  two  longi- 
tudinal layers  with  intermediate  circular  fibres.  These  fibres  are 
most  probably  of  a muscular  nature.  The  vasa  deferentia  of  the  dog, 
cat,  and  rabbit  were  found  by  E.  Weber  to  exhibit  lively  peristaltic 
contractions  when  stimulated  by  means  of  electricity. 

The  surface  of  the  mucous  membrane  is  pale;  it  is  thrown  into  three 


THE  SEMINAL  VESICLES. 


551 


or  four  fine  longitudinal  ridges,  and,  besides  this,  in  the  sacculated 
portion  of  the  duct,  is  marked  by  numerous  finer  rugae  which  enclose 
irregular  polyhedral  spaces,  resembling  in  this  the  lining  membrane  of 
the  vesiculse  seminales.  The  epithelium  is  of  the  columnar  kind. 

Fas  aberrans  (fig.  487,**). — This  name  was  applied  by  Haller  to  a long 
narrow  tube,  or  diverticulum,  discovered  by  him  and  since  very  fre- 
quently met  with,  which  leads  off  from  the  lower  part  of  the  canal  of 
the  epididymis,  or  from  the  commencement  of  the  vas  deferens,  and 
extends  upwards  in  a tortuous  manner  for  two  or  three  inches,  amongst 
the  vessels  of  the  spermatic  cord,  where  it  ends  by  a closed  extremity. 
Its  length,  when  it  is  unravelled,  ranges  from  one  inch  and  a half  to  as 
much  as  fourteen  inches;  and  its  breadth  increases  towards  its  blind 
extremity.  Sometimes  this  diverticulum  is  branched,  and  occasionally 
there  is  more  than  one  such  aberrant  duct.  Its  structure  appears  to 
be  similar  to  that  of  the  vas  deferens,  but  its  office  is  unknown. 

THE  SEMINAL  VESICLES  AND  EJACULATORY  DUCTS. 

The  seminal  vesicles  (vesiculse  seminales;  fig.  479,®,“)  are  two 
membranous  receptacles,  situated,  one  on  each  side,  upon  the  base  of 
the  bladder,  between  it  and  the  rectum.  When  distended  they  form 
two  oblong  sacculated  bodies,  somewhat  flattened  above  but  convex 
below,  widened  behind  and  narrow  in  front.  Their  length  is  usually 
about  two  inches  and  a half,  and  their  greatest  breadth  from  four  to 
six  lines;  but  they  vary  in  size  in  different  individuals,  and  also  on 
opposite  sides  of  the  same  subject. 

Their  upper  surface  is  firmly  attached  to  the  coats  of  the  bladder, 
on  the  under  surface  of  which  they  extend  forwards  and  inwards  from 
near  the  terminations  of  the  two  ureters  to  the  base  of  the  prostate 
gland.  The  posterior  obtuse  extremities  of  the  two  vesiculse  seminales 
are  separated  widely  from  each  other,  but  anteriorly  they  converge  so 
as  to  approach  the  two  vasa  deferentia,  which  run  forwards  to  the 
prostate  between  them.  The  small  triangular  portion  of  the  base  of 
the  bladder,  which  is  marked  off  by  the  two  vesiculse  seminales  at  the 
sides,  and  behind  by  the  line  of  reflection  of  the  peritoneum  from  the 
rectum  to  the  bladder,  rests  immediately  on  that  intestine,  at  least 
there  is  nothing  interposed  but  the  vasa  deferentia.  The  seminal 
vesicles  themselves  are  also  supported  by  the  sides  of  the  rectum,  but 
they  are  separated  from  the  bowel  by  a layer  of  the  recto-vesical 
fascia,  which  holds  them  to  the  base  of  the  bladder. 

The  sacculated  appearance  of  the  vesiculse  seminales  is  owing  to 
their  peculiar  formation.  Each  consists  of  a tube  coiled  on  itself  in  a 
complicated  manner,  and  firmly  held  in  that  condition  by  a very  dense 
fibrous  tissue.  When  unrolled  (see  fig.  479),  this  tube  is  found  to  be 
from  four  to  six  inches  long,  and  about  the  width  of  a quill.  Its  pos- 
terior extremity  is  closed,  so  that  it  forms  a long  cul-de-sac;  but  there 
are  generally,  if  not  always,  several  longer  or  shorter  branches  or 
diverticula  developed  from  it,  which  also  end  by  closed  extremities. 
Its  anterior  extremity,  which  forms  the  fore  part  of  the  vesicula, 
becomes  straight  and  narrowed,  and  ends  opposite  the  base  of  the 
prostate  by  uniting  on  its  inner  side,  at  a very  acute  angle,  with  the 


552 


VESSELS  OF  THE  TESTIS. 


narrow  termination  of  the  corresponding  vas  deferens  to  form  a single 
canal,  which  is  the  common  seminal  or  ejaculatory  duct. 

In  structure,  the  vesiculae  seminales  resemble  very  closely  the 
adjoining  sacculated  portions  of  the  vasa  deferentia.  Besides  an 
external  fibro-cellular  investment,  connected  with  the  recto-vesical 
fascia,  they  have  a proper  coat,  which  is  firm,  dense,  and  somewhat 
elastic,  and  consists  of  rigid  white  fibres,  and  of  others  of  a deep 
yellowish-brown  hue.  In  some  animals  muscular  fibres  have  been 
shown  in  the  coats  of  the  seminal  vesicles,  and,  according  to  E.  H. 
Weber,  they  exist  in  the  human  subject  also.  The  mucous  membrane 
is  pale,  or  has  a dirty  brownish-white  colour.  It  is  traversed  by 
multitudes  of  fine  rugae,  which  form  an  areolar  structure  resembling 
that  seen  in  the  gall-bladder,  but  composed  of  much  finer  meshes : this 
areolar  character,  as  already  stated,  begins  to  appear  in  the  lower 
sacculated  part  of  the  vas  deferens,  and  is  considered  by  Weber  as 
constituting  a species  of  glandular  structure.  The  epithelium  of  the 
vesiculae  is  of  the  squamous  kind:  its  particles  have  a granular 
character. 

The  seminal  vesicles  serve  as  receptacles  or  reservoirs  for  the 
semen,  as  is  easily  proved  by  a microscopic  examination  of  their 
contents ; but,  besides  this,  it  is  supposed  by  some  that  they  secrete 
a peculiar  fluid  which  is  incorporated  with  the  semen. 

The  common  seminal  ducts,  or  ejaculatorij  ducts  (fig.  479,“),  two 
in  number,  are  formed  on  each  side  by  the  junction  of  the  narrowed 
extremities  of  the  corresponding  vas  deferens  and  vesicula  seminalis, 
close  to  the  base  of  the  prostate  gland.  From  this  point  they  run 
forwards  and  upwards,  at  the  same  time  approaching  each  other,  and 
then  pass  side  by  side  through  the  prostate  between  its  middle  and 
two  lateral  lobes.  After  a course  of  nearly  an  inch,  during  which 
they  become  gradually  narrower,  they  end  in  the  floor  of  the  pro- 
static portion  of  the  urethra  by  two  slit-like  orifices,  placed  one  on 
each  prominent  margin  of  the  longitudinal  depression  which  exists  at 
the  anterior  part  of  the  verumontanum,  named  the  sinus  pocularis,  or 
utriculus  virilis.  For  a short  distance  the  ejaculatory  ducts  run  in  the 
substance  of  the  walls  of  this  sinus.  (See  p.  535.) 

The  coats  of  the  common  seminal  duct,  as  compared  with  those  of 
the  vas  deferens  and  vesicula,  are  very  thin.  The  strong  outer  tunic 
almost  entirely  disappears  after  the  entrance  of  the  ducts  between  the 
lobes  of  the  prostate;  and  the  mucous  membrane  becomes  gradually 
smoother,  and  at  length  passes  into  that  of  the  urethra. 

It  is  along  these  ejaculatory  ducts  that  the  fluid  contained  in  the 
seminal  vesicles  and  vas  deferens  is  forced  into  the  urethra. 

VESSELS  AND  NERVES  OF  THE  TESTIS. 

The  testicle  and  its  excretory  apparatus  receive  blood-vessels  and 
nerves  from  different  sources  from  those  which  supply  the  coverings 
of  those  parts. 

The  spermatic  artery,  or  proper  artery  of  the  testicle  (vol.i.  p.  602),  is  a 
slender  and  remarkably  long  branch,  wdiich  arises  from  the  abdominal 
aorta,  and  reaching  the  spermatic  cord,  descends  along  it  to  the  gland. 


THE  SEMEN. 


553 


In  early  foetal  life  its  course  is  much  shorter,  as  the  testis  is  then 
situated  near  the  part  of  the  aorta  from  which  the  artery  arises.  As 
the  vessel  approaches  the  testicle,  it  gives  off  small  branches  to  the 
epididymis,  and  then  divides  into  others  which  perforate  the  tunica 
albuginea  at  the  back  of  the  gland,  and  pass  through  the  corpus  High- 
morianum  ; some  spread  out  on  the  internal  surface  of  the  tunica 
albuginea,  whilst  others  run  along  between  the  lobes  of  the  testis, 
supported  by  the  fibrous  processes  of  the  mediastinum.  The  smallest 
branches  ramify  on  the  delicate  membranous  septa  between  the  lobes, 
before  supplying  the  seminiferous  tubes. 

The  vas  deferens  receives  from  the  superior  vesical  artery  a long 
slender  branch,  which  accompanies  the  duct,  and  is  hence  named  the 
deferent  artery,  or  artery  of  the  vas  deferens  (p.  610).  It  ramifies  on 
the  coats  of  the  duct,  and  reaches  as  far  as  the  testis,  where  it  anas- 
tomoses with  the  spermatic  artery. 

The  spermatic  veins  (vol.  ii.  p.  29.)  commence  in  the  testis  and  epi- 
didymis, pass  out  at  the  posterior  border  of  both,  and  unite  into  larger 
vessels,  which  freely  communicate  with  each  other  as  they  ascend  along 
the  cord,  and  form  a plexus,  named  the  pampiniform  plexus.  Ultimately 
two  or  three  veins  follow  the  course  of  the  spermatic  artery  into  the 
abdomen,  where  they  unite  into  a single  trunk,  that  of  the  right  side 
opening  into  the  vena  cava,  and  that  of  the  left  into  the  left  renal  vein. 

The  lymphatics  (p.  51)  accompany  the  spermatic  vessels  and  ter- 
minate in  the  lumbar  lymphatic  glands,  which  lie  about  the  large 
blood-vessels  in  front  of  the  vertebral  column. 


The  nerves  are  derived  from  the  sympathetic  system.  The  sper- 
matic plexus  (p.  351)  is  a very  delicate  set  of  nervous  filaments,  which 
descend  upon  the  spermatic  artery  from  the  aortic  plexus.  Some  ad- 
ditional filaments,  which  are  very  minute,  come  from  the  hypogastric 
plexus,  and  accompany  the  artery  of  the  vas  deferens. 

The  vesiculae  seminales  receive  branches  from  the  inferior  vesical 
and  middle  haemorrhoidal 


arteries.  The  veins  and 
lymphatics  correspond.  The 
nerves  belong  to  the  sym- 
pathetic system,  and  come 
from  the  hypogastric  plexus. 

The  semen  is  a thick  whitish 
fluid,  which  consists  of  a liquor 
seminis,  and  of  certain  solid  par- 
ticles. 

The  liquor  seminis  is  colour- 
less, transparent,  and  of  an  al- 
buminous nature.  It  contains 
floating  in  it,  besides  squamous 
and  columnar  epithelium  cells, 
oil-like  globules  and  minute 
granular  matter,  two  principal 
microscopic  constituents,  named 
the  seminal  granules  (Wagner), 
and  the  seminal  animalcules,  sper- 
matozoa or  spermatic  filaments. 

The  seminal  granules  (fig.  489,“) 
are  rounded  colourless  corpus- 


Fig.  489. 


Spermatozoa  from  man,  and  their  development. 
(W,agner). — A.  Spermatozoa  from  the  semen  of  the  vas 
deferens.  1 to  4.  Show  their  variety  ot  character.  5. 
Seminal  granules — B.  Contents  of  the  semen  of  the  tes- 
tis. 1.  Large  round  corpuscle  or  cell.  2.  A cell  con- 
taining three  roundish  granular  bodies,  from  which  the 
spermatozoa  are  developed.  3.  A fasciculus  of  sperma- 
tozoa, as  they  are  seen  grouped  together  in  the  testis. 


VOL.  II. 


47 


554 


T{IE  VULVA. 


cles,  having  a granular  aspect.  They  average  about  ^.n  inch  in  dia- 

meter, and  may  be  allied  to  mucous  corpuscles. 

The  spermatozoa  (fig.  489,  a,)  are  peculiar  particles,  endowed  with  a power  of 
executing  a brisk  lashing  movement.  Each  consists  of  a flattened  oval  part  or 
so-called  body,  and  of  a long  filiform  tail.  The  body  is  about  ^-„V^th  of  an  inch 
in  width,  and  the  entire  spermatozoon  is  from  j^„th  to  j-K^th  of  an  inch  in  length. 
The  body  often  contains  a spot,  and,  at  its  junction  with  the  narrow  part  or  tail, 
there  is  frequently  a slight  projecting  fringe  or  collar.  The  spermatozoa  are  deve- 
loped in  the  interior  of  nucleated  cells,  which  become  enlarged  into  transparent 
vesicular  bodies  of  considerable  size  (b). 

ORGANS  OF  GENERATION  IN  THE  FEMALE. 

The  generative  organs  in  the  female  consist  of  the  ovaries,  uterus, 
and  Fallopian  tubes,  which  are  named  the  internal,  and  the  vagina 
and  vulva,  named  the  external  organs  of  generation. 

The  vulva,  or  pudendum,  is  a general  term,  w'hich  includes  all  the 
parts  perceptible  externally,  viz.,  the  mons  Veneris,  the  labia,  the 
hymen  or  carunculse,  the  clitoris,  and  the  nymphm.  The  orifice  of 
the  urethra  also  requires  to  be  noticed  in  connexion  with  these 
parts. 

The  integument  on  the  fore  part  of  the  pubic  symphysis  is  elevated 
by  a quantity  of  cellular  and  adipose  substance  deposited  beneath  it, 
and  is  covered  with  hair.  This  part  surmounts  the  labia,  and  has 
been  called  mons  Veneris.  The  labia  pudendi  (labia  externa  v. 
majora)  extend  downwards  and  backwards  from  the  mons,  gradually 
becoming  thinner  as  they  descend.  They  form  two  rounded  folds  of 
integument  so  placed  as  to  leave  an  elliptic  interval  (rima)  between 
'them,  the  outer  surface  of  each  being  continuous  with  the  skin,  and 
covered  with  scattered  hairs,  whilst  the  inner  is  lined  by  the  com- 
mencement of  the  genito-urinary  mucous  membrane.  Between  the 
skin  and  mucous  membrane  there  is  found,  besides  fat,  vessels,  nerves, 
and  glands,  some  tissue  resembling  that  of  the  dartos  in  the  scrotum 
of  the  male.  The  labia  majora  unite  beneath  the  mons  and  also  in 
front  of  the  perineum,  the  two  points  of  union  being  called  commis- 
sures. The  posterior  or  Inferior  one  is  about  an  inch  distant  from  the 
margin  of  the  anus,  the  interval  between  them  being  named  the  peri- 
neum. Immediately  within  the  posterior  commissure,  the  labia  are 
connected  by  a slight  transverse  fold  {frcenulum  pudendi)  which  has 
also  received  the  name  oi fourchette,  and  is  commonly  torn  in  the  first 
parturition.  The  space  between  it  and  the  commissure  has  been 
called /oss«  navicularis. 

Beneath  the  anterior  commissure,  and  concealed  between  the  labia, 
is  the  clitoris  (fig.  '490/),  a small  elongated  body  analogous  in  com 
formation  and  structure  to  a diminutive  penis,  though  differing  in  not 
being  perforated  by  the  canal  of  the  urethra,  and  also  in  not  having 
the  corpus  spongiosum  attached  along  beneath  it.  It  consists  of  two 
corpora  cavernosa,  which  are  attached  by  crura  (I)  to  the  rami  of  the 
ischium  and  pubes,  and  are  united  together  by  their  flattened  inner 
surfaces,  which  form  an  incomplete  pectiniform  septum.  The  body  of 
the  clitoris,  which  is  very  short  and  hidden  beneath  the  mucous  mem- 
brane, is  surmounted  by  a small  glans  (e),  consisting  of  spongy  erectile 
tissue.  The  glans  is  imperforate,  but  highly  sensitive,  and  covered 


THE  CLITORIS. 


555 


with  a membranous  fold,  analogous 
to  the  prepuce.  There  is  a small 
suspensory  ligament  (fig.  491),  like 
that  of  the  penis ; and  the  two  ischio- 
cavernous muscles,  here  named  erec- 
tores  clitoridis,  have  the  same  con- 
nexions as  in  the  male,  being  inserted 
into  the  crura  of  the  corpora  caver- 
nosa. 

From  the  glans  and  preputial  co- 
vering of  the  clitoris  two  narrow 
folds  of  mucous  membrane,  in  form 
not  unlike  a cock’s  comb,  descend 
obliquely  outwards  for  about  an  inch 
and  a half,  one  on  each  side  of  the 
entrance  of  the  vagina.  These  are 
the  nym-phcR  (labia  interna  v.  minora). 
Their  inner  surface  is  continuous 


Fig.  490. 


with  that  of  the  vagina  ; the  external  Lateral  view  of  the  erectile  structures 
insensibly  passes  into  that  of  the  labia  the  external  organs  of  generation  in  the 

rpL-  _ . • 1 /c_  female,  the  skin  and  raucous  membrane 

majora.  They  contain  vessels  (fig.  being  removed  (Kobelt). — a.  Bulbus  vesli- 
491,  g)  between  the  laminae  of  tegu-  buli.  c.  Plexus  of  veins  named  pars  inter- 

mpntnrvr  mpmhranp  hnt  nppnrrtino-  «•  Gians  of  the  clitoris.  /.  Body  of 

memaiy  memorane,  out,  accoraing  the  clitoris,  a.  Dorsal  vein.  l.  Right  crus 

to  Kobelt,  no  erectile  plexus  ; indeed  of  clitoris,  m.  Vulva,  n.  Right  gland  of 

they  would  seem  to  correspond  to  ^^rthoime. 

the  cutaneous  covering  of  the  male  urethra  (supposed  to  be  split  open), 
whilst  the  erectile  structure  corresponding  to  the  bulb  and  spongy 
body  (supposed  to  be  in  two  halves)  lies  deeper,  as  will  be  presently 
explained. 

Fig.  491. 


Front  view  of  the  erectile  structures  of  the  external  organs  of  generation  in  the  female. — a. 
Bulbus  veslibuli.  b.  Sphincter  vaginse  muscle,  e,  e.  Venous  plexus,  or  pars  intermedia,  f. 
Gians  of  the  clitoris,  g.  Connecting  veins,  h.  Dorsal  vein  of  the  clitoris,  k.  Veins  going 
beneath  pubes.  1.  The  obturator  vein. 


556 


THE  HYMEN. 


Between  the  nymphae,  is  the  angular  interval  called  the  vestihule.,  in 
which  is  situated  the  circular  orifice  of  the  urethra,  or  meatus  urinarius, 
about  an  inch  below  the  clitoris  and  just  above  the  entrance  to  the 
vagina.  The  membrane  which  surrounds  this  orifice  is  rather  promi- 
nent in  most  instances,  so  as  readily  to  indicate  its  situation.  The 
urethra  itself  has  been  already  described  (see  p.  524). 

Immediately  below  the  orifice  of  the  urethra  is  the  entrance  to  the 
vagina,  which,  in  the  virgin,  is  usually  more  or  less  narrowed  by  the 
hymen.  This  is  a thin  duplicature  of  the  mucous  membrane,  placed 
at  the  lateral  and  inferior  parts  of  the  entrance  of  the  vagina;  its  form 
varies  very  considerably  in  different  persons,  but  is  most  frequently 
semilunar,  the  concave  margin  being  turned  obliquely  upwards  or 
towards  the  pubes.  Sometimes  it  is  circular  and  is  perforated  only 
by  a small  round  orifice,  placed  usually  a little  above  the  centre;  and 
occasionally  it  is  cribriform,  or  pierced  with  several  small  apertures; 
and  it  may  completely  close  the  vagina,  constituting  imperforate 
hymen.  On  the  other  hand,  it  is  often  reduced  to  a mere  fringe,  or  it 
may  be  entirely  absent.  After  its  rupture,  some  small  rounded  eleva- 
tions remain,  called  carunculce  myrtiformes. 

The  mucous  membrane  may  be  traced  inwards  from  the  borders  of 
the  labia  majora,  where  it  is  continuous  with  the  skin : it  forms  a fold 
over  the  vascular  tissue  of  the  nymphae,  and  is  then  prolonged  into  the 
urethra  and  vagina.  It  is  smooth,  reddish  in  colour,  is  covered  by  a 
scaly  epithelium,  and  is  provided  with  a considerable  number  of 
mucous  crypts  and  follicles,  and  with  glands  which  secrete  an  unctuous 
and  odorous  substance.  The  mucous  crypts  and  follicles  are  espe- 
cially distinct  on  the  inner  surface  of  the  nymphae,  and  near  the  orifice 
of  the  urethra.  The  sebaceous  glands  are  found  beneath  the  prepuce, 
and  upon  the  labia  majora  and  outer  surface  of  the  nymphae. 

The  glands  of  Bartholine  (fig.  490,  n)  analogous  to  Cowper’s  glands 
in  the  male,  are  two  reddish-yellow  round  or  oval  bodies,  about  the 
size  of  a large  pea  or  small  bean,  lodged  one  on  each  side  of  the  com- 
mencement of  the  vagina,  between  it  and  the  erectores  clitoridis 
muscles,  beneath  the  superficial  perineal  fascia,  and  in  front  of  the 
transverse  muscles.  Their  ducts,  which  are  long  and  single,  run 
forward  and  open  on  the  inner  aspect  of  the  nymphae,  outside  the 
hymen  or  carunculae  myrtiformes. 

Erectile  tissue. — All  the  parts  of  the  vulva  are  supplied  abundantly 
with  blood-vessels,  and  in  certain  situations  there  are  masses  composed 
of  venous  plexuses,  or  erectile  tissue,  which  are  analogous  to  those 
found  in  the  male.  The  corpora  cavernosa  and  glans  clitoridis  have 
already  been  described.  Besides  these  there  are  two  large  leech-shaped 
masses  (figs.  490,  491,  a)  about  an  inch  long,  consisting  of  a network 
of  veins,  enclosed  in  a fibrous  membrane,  and  lying  one  on  each  side 
of  the  vestibule,  a little  behind  the  nymphae.  They  are  rather  pointed 
at  their  upper  extremities,  and  rounded  below  ; they  are  suspended,  as 
it  were,  to  the  crura  of  the  clitoris  and  the  rami  of  the  pubes,  covered 
internally  by  the  mucous  membrane,  and  embraced  on  the  outer  side 
by  the  fibres  of  the  constrictor  vaginae  muscle  (fig.  491,  b).  These 
two  plexiform  masses  were  known  to  many  of  the  older  anatomists, 


THE  VAGINA. 


557 


but  have  been  more  recently  noticed  by  Taylor  and  Guthrie,  and 
particularly  described  and  figured  by  Kobelt.  They  are  named  by 
the  latter  bulbi  vestibuli,  (plexus  retiformes,  De  Graaf;  crura  clitoridis 
interna,  Swammerdam;  corpora  cavernosa,  Santorini;  semi-bulbs, 
Taylor,)  and  are  considered  by  that  observer  to  be  analogous  to  the 
bulb  of  the  urethra  in  the  male,  which  it  will  be  remembered  presents 
traces  of  a median  division.  In  front  of  the  bipartite  bulb  of  the 
vestibule,  is  a smaller  plexus  on  each  side  (fig.  490,  c,  fig.,  491,  e e), 
the  vessels  of  which  are  directly  continuous  with  those  of  the  bulbus 
vestibuli  behind,  and  of  the  glans  clitoridis  before.  This  is  the  pars 
intermedia  of  Kobelt,  and  is  regarded  by  him  as  the  analogue  of  the 
part  of  the  male  corpus  spongiosum  urethrae  which  succeeds  the 
bulb:  it  receives  large  veins  coming  direct  from  the  nymphae. 

Vessels. — The  outermost  parts  of  the  vulva  are  supplied  by  the 
superficial  pudendal  arteries;  the  deeper  parts  and  all  the  erectile 
tissues  receive  branches  from  the  internal  pudic  arteries,  as  in  the 
male.  The  veins  also  in  a great  measure  correspond : there  is  a vena 
dorsalis  clitoridis  {h),  receiving  branches  from  the  glans  and  other 
parts  as  in  the  male;  the  veins  of  the  bulbus  vestibuli  pass  backwards 
into  the  vaginal  plexuses,  and  communicate  also  with  the  obturator 
veins  (/) ; above,  they  communicate  with  the  veins  of  the  pars  inter- 
media, those  of  the  corpora  cavernosa  and  of  the  glans  of  the  clitoris, 
and  also  with  the  vena  dorsalis.  The  lymphatics  accompany  the 
blood-vessels. 

Nerves. — Besides  sympathetic  branches,  which  descend  along  the 
arteries,  especially  for  the  erectile  tissues,  there  are  other  nerves  pro- 
ceeding from  the  lumbar  and  sacral  plexuses;  those  from  the  former 
being  the  branches  of  the  genito-crural  (p.  323),  and  those  from  the 
latter,  of  the  inferior  pudendal  and  internal  pudic  nerves  (p.  331), 
which  last  sends  comparatively  large  branches  to  the  clitoris. 

THE  VAGINA. 

The  vagina  is  a membranous  and  dilatable  tube,  extending  from  the 
vulva  to  the  uterus,  the  neck  of  which  is  embraced  by  it.  It  rests 
below  and  behind  on  the  rectum,  supports  the  bladder  and  urethra  in 
front,  and  is  enclosed  between  the  levatores  ani  muscles  at  the  sides. 
Its  direction  is  oblique  from  below  upwards  and  backwards,  in  which 
course  it  is  also  slightly  curved,  the  concavity  of  the  curve  being 
turned  upwards  and  forwards.  The  axis  of  the  vagina  corresponds, 
therefore,  first,  with  that  of  the  outlet  of  the  pelvis,  and  higher  up  with 
that  of  the  pelvic  cavity.  In  consequence  of  being  thus  curved,  its 
length  will  be  found  greater  if  measured  along  the  lower  than  along 
the  upper  wall,  being  in  the  latter  situation  about  four  inches,  while  in 
the  former  it  amounts  to  five  or  six.  Each  end  of  the  vagina  is  some- 
what narrower  than  the  middle  part : the  lower,  v.’hich  is  continuous 
with  the  vulva,  is  the  narrowest  part,  and  has  its  long  diameter  from 
before  backwards ; the  middle  part  is  the  widest  from  side  to  side, 
being  flattened  from  before  backwards,  so  that  its  anterior  and  pos- 
terior walls  are  ordinarily  in  contact  with  each  other;  at  iis  upper 
end  it  is  rounded,  and  expands  to  receive  the  vaginal  portion  of  the 

47* 


558 


THE  VAGINA. 


neck  of  the  uterus,  which  is  embraced  by  it  at  some  distance  from  the 
os  uteri.  The  vagina  reaches  higher  up  on  the  cervix  uteri  behind 
than  in  front,  so  that  the  uterus  appears,  as  it  were,  to  be  let  into  its 
anterior  wall. 

On  the  inner  surface  of  the  vagina,  along  the  anterior  (fig.  493,  e) 
and  the  posterior  walls,  a slightly  elevated  ridge  extends  from  the 
lower  end  upwards  along  the  middle  line,  similar  to  the  raphe  in  other 
situations  : these  ridges  are  named  the  columns  of  the  vagina,  or  co- 
lumnce  I'ugarum.  Numerous  dentated  transverse  ridges,  called  rugce, 
will  also  be  observed,  particularly  in  persons  who  have  not  borne 
children,  running  at  right  angles  from  the  columns.  These  columns 
and  rugae,  which  are  most  evident  near  the  entrance  of  the  vagina, 
and  gradually  become  less  marked  and  disappear  towards  its  upper 
end,  are  calculated  to  facilitate  the  enlargement  of  the  vagina  that 
occurs  during  pregnancy  and  parturition. 

Structure,  and  connexions. — The  walls  of  the  vagina  are  thickest  in 
front,  where  the  urethra  is  situated,  which  indeed  may  be  said  to  be 
imbedded  in  the  anterior  wall  of  the  vaginal  passage;  in  other  situa- 
tions they  are  thinner.  The  vagina  is  firmly  connected  by  cellular 
tissue  to  the  neck  of  the  bladder,  and  but  loosely  to  the  rectum  and 
levatores  ani  muscles ; at  the  upper  end,  for  about  a fourth  part  of  its 
length,  it  receives  a covering  behind  from  the  peritoneum, which  de- 
scends in  the  form  of  a cul-de-sac  thus  far  between  the  vagina  and  the 
rectum. 

The  external  layer  of  which  the  vagina  is  composed  is  a dense, 
pale  red,  highly  distensible  and  vascular  cellular  tissue,  which  adheres 
closely  above  to  the  tissue  of  the  cervix  uteri.  Round  the  lube  a layer 
of  loose  erectile  tissue  is  found,  which  is  most  marked  at  the  lower 
part. 

At  its  lower  end,  the  vagina  is  embraced  by  muscular  fibres,  which 
constitute  the  sphincter  vagince  (fig.  491,  h).  The  fibres  of  this  mus- 
cle are  attached  behind  to  the  central  point  of  the  perineum,  in  com- 
mon with  the  sphincter  ani  and  transversus  perinaei  muscles ; they 
open  out  to  surround  the  vaginal  orifice  and  vestibule,  closely  em- 
bracing on  the  outer  side  the  two  bulbs  of  the  vestibule,  and  again 
approaching  in  front,  become  narrow  and  are  inserted  upon  the  cor- 
pora cavernosa  of  the  clitoris,  a fasciculus  crossing  over  these  and 
including  the  vena  dorsalis.  The  two  halves  of  this  elliptical  muscle 
appear  to  be  strictly  analogous  to  those  of  the  bulbo-cavernosus  mus- 
cle in  the  male. 

The  mucous  membrane,  besides  the  columns  and  rugae,  is  provided 
with  numerous  muciparous  glands  and  follicles,  especially  in  its  upper 
smoother  portion : around  the  cervix  uteri  they  are  very  numerous. 
This  membrane,  which  is  continuous  with  that  of  the  uterus,  is  covered 
by  a squamous  epithelium. 

The  vagina  is  largely  supplied  with  vessels  and  nerves.  The  arte- 
ries are  derived  from  branches  of  the  internal  iliac,  viz.,  the  vaginal,  in- 
ternal pudic,  vesical,  and  uterine  (vol.  i.  pp.  610,613).  The  veins  corre- 
spond ; but  they  first  surround  the  vagina  with  numerous  branches,  and 
form  at  each  side  a plexus  named  the  vaginal  plexus.  The  nerves  &xe 


THE  UTERUS. 


559 


derived  from  the  hypogastric  plexus  of  the  sympathetic,  and  from  the 
fourth  sacral  nerve  and  pudic  nerve  of  the  spinal  system  ; the  former 
are  traceable  to  the  erectile  tissue  (vol.  ii.  p.  356). 

UTERUS. 

The  uterus,  womb,  or  matrix  (fig.  492,  b),  is  a hollow  organ,  having 
very  thick  walls,  which  is  intended  to  receive  the  ovum,  retain  and 
support  it  during  the  development  of  the  foetus,  and  expel  it  at  the  time 


Fig.  492. 


Anterior  view  of  the  uterus  and  appendages. — a.  Fundus,  h,  body,  and  c,  cervix  or  nec  k of  the 
uterus,  e.  Front  of  the  upper  part  of  the  vagina,  n,  n.  Round  ligaments  of  the  uterus,  r,  t. 
Broad  ligaments,  .x,  s.  Fallopian  tubes.  <.  Fimbriated  extremity,  u.  Ostium  abdominale.  The 
position  of  the  ovaries  is  shown  through  the  broad  ligaments  ; and  also  the  cut  edge  of  the  peri- 
toneum, along  the  lower  border  of  the  broad  ligaments  and  across  the  uterus. 

of  parturition.  During  pregnancy  this  organ  accordingly  undergoes 
a great  enlargement  in  size  and  capacity,  as  well  as  other  important 
changes.  It  is  a pear-shaped  bod)^  situated  in  the  cavity  of  the  pelvis, 
between  the  bladder  and  rectum,  and  projecting  into  the  upper  end  of 
the  vagina  (e),  with  which  it  is  intimately  connected.  In  its  ordinary 
condition  the  uterus  does  not  reach  above  the  brim  of  the  pelvis.  Its 
upper  end  is  turned  upwards  and  forwards,  whilst  the  lower  is  in  the 
opposite  direction;  so  that  its  position  corresponds  with  that  of  the 
axis  of  the  inlet  of  the  pelvis,  and  forms  an  angle  or  curve  with  the 
axis  of  the  vagina,  which  corresponds  with  that  of  the  cavity  and 
outlet.  The  uterus  projects,  as  it  were,  upwards  into  a fold  of  the 
peritoneum,  by  which  it  is  covered  behind  and  above,  and  also  in 
front,  except  for  a short  distance  towards  the  lower  end,  where  it  is 
connected  with  the  base  of  the  bladder.  Its  free  surface  is  in  contact 
with  the  other  pelvic  viscera,  some  convolutions  of  the  small  intestine 
usually  lying  upon  and  behind  it.  From  its  two  sides  the  peritoneum 
is  reflected  in  the  form  of  a broad  duplicature,  named  the  ligamentum 
latum  (r),  which,  together  with  the  parts  contained  within  it,  will  be 
presently  described. 

The  fully  developed  virgin  uterus,  for  to  that  condition  of  the  organ 
the  following  description  applies,  is  pyriform,  but  compressed  from 


560 


THE  UTERUS. 


before  backwards,  and,  therefore,  somewhat  triangular,  the  base  being 
turned  upwards.  Its  average  dimensions  are  about  three  inches  in 
length,  two  in  breadth  at  its  upper  and  wider  part,  and  nearly  an  inch 
in  thickness:  its  weight  is  from  seven  to  twelve  drachms.  It  is  usually 
described  as  consisting  of  the  fundus,  the  body,  and  the  neck. 

The  fundus  (o).is  the  broad  upper  end  which  surmounts  the  body, 
and  e-Ktends  beyond  the  points  of  attachment  of  the  Fallopian  tubes. 
Its  border  is  convex,  and  it  is  covered  entirely  with  peritoneum.  The 
succeeding  part,  or  body  (b),  gradually  narrow’s  as  it  extends  from  the 
fundus  to  the  neck  ; its  two  sides  or  borders  are  straight ; its  anterior 
and  posterior  surfaces  are  both  somewhat  convex,  but  the  latter  more 
so  than  the  former.  At  the  points  of  union  of  the  sides  with  the 
rounded  superior  border  or  fundus,  are  two  projecting  angles,  to  which 
the  Fallopian  tubes  are  attached,  the  round  ligaments  being  inserted 
a little  before,  and  the  ovarian  ligaments  behind  and  beneath  them;  all 
three  of  these  parts  being  included  in  the  duplicature  of  the  broad 
ligaments.  The  lower,  narrower,  and  more  rounded  portion  of  the 
uterus  is  named  the  neck  or  cervix  uteri  {c) ; it  is  from  four  to  six  lines 
long;  it  is  continuous  above  with  the  body,  and,  becoming  somew'hat 
smaller  towards  its  lower  extremity,  projects  into  the  upper  end  of  the 
tube  of  the  vagina,  which  is  attached  all  around  to  the  substance  of 
the  uterus,  but  extends  upwards  to  a greater  distance  behind  than  in 
front.  The  projecting  portion  is  sometimes  named  the  vaginal  part 
(pars  uteri  vaginalis;  fig.  493,  d).  The  lower  end  of  the  uterus  pre- 
sents a transverse  aperture,  by  which  its  cavity  opens  into  the  vagina  j 
this  is  named  variously  os  uteri,  os  uteri  externum,  and  (from  some 
supposed  likeness  to  the  mouth  of  the  tench  fish)  os  tincce.  It  is  bound- 
ed by  two  thick  lips,  which  are  distinguished  by  their  relative  position 
into  anterior  and  posterior,  the  latter  being  the  thinner  and  longer  of 
the  two.  These  borders  or  lips  are  generally  smooth,  but,  after  par- 
turition, frequently  become  irregular,  and  are  sometimes  fissured  or 
cleft. 

Owing  to  the  great  thickness  of  its  walls  (fig.  493,/),  the  cavity  of 
the  uterus  is  very  small  in  proportion  to  the  size  of  the  organ.  The 
part  corresponding  with  the  body  (/;)  is  triangular,  and  flattened  from 
before  backwards,  so  that  its  anterior  and  posterior  walls  touch  each 
other.  The  base  of  the  triangle  is  directed  upwards,  and  is  curvili- 
near, the  convexity  being  turned  towards  the  interior  of  the  uterus. 
This  form  is  owing  to  the  prolongation  of  the  cavity  through  the  sub- 
stance of  the  organ  towards  its  two  superior  angles  (/),  where  two 
minute  foramina  will  be  observed,  leading  into  the  Fallopian  tubes  (s). 
At  the  point  where  the  body  is  continuous  below  with  the  neck,  the 
cavity  is  slightly  constricted,  and  thus  forms  what  is  sometimes  named 
the  internal  orifice  {os  uteri  internum,  isthmus  vel  ostium  uteri) ; it  is 
often  smaller  than  the  os  externum,  and  is  a circular  opening.  That 
portion  of  the  cavity  which  corresponds  to  the  neck  (c)  resembles  a 
tube  slightly  flattened  before  and  behind  ; it  is  somewhat  dilated  in  the 
middle,  and  opens  inferiorly  into  the  vagina  by  the  os  tincse.  Its  inner 
surface  is  marked  by  two  longitudinal  ridges  or  columns,  which  run, 
one  on  the  anterior,  the  other  on  the  posterior  wall,  and  from  both  of 


STRUCTURE  OF  THE- UTERUS. 


561 


which,  rug£e  are  directed  obliquely  upwards  on  each  side,  so  as  to 
present  an  appearance  which  has  been  named  arhor  vitce  uterinus, 
also  palmcB  plicatcB. 

Structure. — The  walls  of  the  uterus  consist  of  an  external  serous 
layer,  an  internal  mucous  membrane,  and  a proper  intermediate  tissue. 
The  peritoneal  layer  covers  the  fundus  and  body,  except  at  the  sides 
and  for  about  half  an  inch  of  the  lower  part  of  the  body  in  front, 
which  is  attached  to  the  base  of  the  bladder. 

The  proper  tissue  of  the  uterus  constitutes  almost  the  entire  substance 
of  its  walls,  which  are  thickest  opposite  the  middle  of  the  body  and 
fundus,  and  are  thinnest  at  the  entrances  of  the  Fallopian  tubes.  The 
tissue  is  very  dense ; it  is  composed  of  bundles  of  muscular  fibres  of 
the  plain  variety,  interlacing  with  each  other,  but  disposed  in  bands 
and  layers,  intermixed  with  much  fibro-cellular  tissue,  a large  number 
of  blood-vessels  and  lymphatics,  and  a few  nerves.  The  cellular 
tissue  is  more  abundant  near  the  outer  surface.  The  arrangement  of 
the  muscular  fibres  is  best  studied  in  the  uterus  at  the  full  period  of 
gestation,  in  which  the  bands  and  layers  formed  by  them  become  aug- 
mented in  size,  and  much  more  distinctly  developed.  They  may  be 
referred  to  three  sets  or  orders,  viz.,  external,  internal,  and  inter- 
mediate. Those  of  the  external  set  are  arranged  partly  in  a thin 
superficial  sheet,  immediately  beneath  the  peritoneum,  and  partly  in 
bands  and  incomplete  strata,  situated  more  deeply.  A large  share  of 
these  fibres  arch  transversely  over  the  fundus  and  adjoining  part  of  the 
body  of  the  organ,  and  converge  at  either  side  towards  the  commence- 
ment of  the  round  ligaments,  along  which  they  are  prolonged  to  the 
groin.  Others  pass  off  in  like  manner  to  the  Fallopian  tubes,  and 
strong  transverse  bands  from  an  anterior  and  posterior  surface  are  ex- 
tended into  the  ovarian  ligaments.  A considerable  number  of  thinly 
scattered  fibres  also  pass  at  each  side  into  the  duplicature  of  the  broad 
ligament,  and  others  are  described  as  running  back  from  the  cervix  of 
the  uterus  into  the  recto- uterine  folds  or  plicae  semilunares.  The 
fibres  of  the  subperitoneal  layer  are  much  mixed  with  cellular  tissue, 
especially  about  the  middle  of  the  anterior  and  posterior  surfaces  of 
the  uterus,  in  which  situation  many  of  the  superficial  fibres  appear  to 
have  as  it  were  a median  attachment  from  which  they  diverge.  The 
fibres  on  the  inner  surface  of  the  uterus  are  disposed  with  comparative 
regularity  in  its  upper  part,  being  arranged  there  in  numerous  con- 
centric rings  round  the  openings  of  the  two  Fallopian  tubes,  the  outer- 
most and  largest  circles  of  the  two  series  meeting  from  opposite  sides 
in  the  middle  of  the  uterus.  Towards  the  cervix  the  internal  fibres 
run  more  transversely  ; elsewhere  they  take  various  directions.  The 
intermediate  fibres,  between  the  external  and  internal  set,  pass  in  bands 
among  the  blood-vessels,  following  no  regular  course. 

The  mucous  membrane  which  lines  the  uterus  is  thin  and  closely 
adherent  to  the  subjacent  substance,  especially  in  the  body  of  the 
organ.  It  is  continued  from  the  vagina,  and  into  the  Fallopian  tubes. 
Between  the  rugre  of  the  cervix,  already  described,  it  is  provided  with 
numerous  mucous  follicles  and  glands.  There  are  also  occasionallv 
found  in  the  same  situation  certain  small  transparent  vesicular  bodies. 


562 


LIGAMliNTS  OF  THE  UTERUS. 


which,  from  an  erroneous  opinion  as  to  their  nature,  were  named  the 
ovula  of  Naboth.  They  appear  to  be  closed  and  obstructed  mucous 
follicles,  distended  with  a clear  viscous  fluid. 

In  the  body  of  the  uterus  the  mucous  membrane  is  thin,  smooth, 
soft,  and  of  a reddish-white  colour.  When  seen  by  aid  of  a lens,  it  is 
found  to  be  marked  over  with  minute  dots,  which  are  the  orifices  of 
numerous  simple  tubular  glands,  somewhat  like  those  of  the  intestine. 
Some  of  these  tubular  glands  are  branched,  and  others  are  slightly 
twisted  into  a coil.  These  glands  can  be  distinctly  seen  in  the  unim- 
pregnated and  in  the  virgin  uterus,  but  they  become  enlarged  and 
more  conspicuous  on  impregnation.  The  epithelium  is  columnar  and 
ciliated  as  far  down  as  the  middle  of  the  cervix,  below  which  point  it 
becomes  squamous  like  that  of  the  vagina  and  vulva. 

Ligaments  of  the  uterus. — Where  the  peritoneum  is  reflected  off 
from  the  uterus  to  the  rectum  behind,  and  to  the  bladder  in  front,  it 
forms,  in  each  position,  two  semilunar  folds,  which  are  sometimes 
called  respectively  the  anterior  and  the  posterior  ligaments  of  the 
uterus.  The  former  are  also  named  the  vesico-uterine,  and  the  latter, 
which  are  more  marked,  the  recto-uterine  folds,  ox  plicae  semilunares 
of  Douglas. 

The  broad  ligaments  (ligamenta  lata,  fig.  492,  493,  r)  are  formed 
on  each  side  by  a fold  of  the  peritoneum,  which  is  directed  laterally 
from  the  anterior  and  posterior  surfaces  of  the  uterus,  to  be  connected 

Fig-.  493. 


of  the  uterus,  laid  open.  The  arbor  vitoe  is  shown  in  tlie  cervix,  d.  The  os  uteri  externum, 
laid  open.  e.  The  interior  of  the  upper  part  of  the  vagina.  /.  Section  of  the  walls  of  the 
uterus,  i.  Opening  into  Fallopian  tube.  o.  Ovary,  p.  Ligament  of  ovary,  r.  Broad  ligament, 
s.  Fallopian  tube.  t.  Fimbriated  extremity. 

with  the  sides  of  the  pelvic  cavity.  The  part  intervening  between  the 
uterus  and  the  pelvis  on  each  side  constitutes  the  ligamentum  latum. 
Between  the  two  layers  of  the  serous  membrane  are  placed,  first, 
the  Fallopian  tube,  which,  as  will  be  more  particularly  described, 
runs  along  the  upper  margin  of  the  broad  ligament;  secondly,  the 
round  ligament,  which  is  in  front;  thirdly,  the  ovary  and  its  liga- 


VESSELS  AND  NERVES  OF  UTERUS. 


568 


ment,  which  are  behind;  and,  lastly,  blood-vessels,  lymphatics,  and 
nerves,  with  some  scattered  fibres  from  the  superficial  muscular  layer 
of  the  uterus.  The  ligament  of  the  ovary  (fig.  493,  f)  is  merely  a 
dense  fibro-cellular  cord,  containing  also,  according  to  some  autho- 
rities, uterine  muscular  fibres,  and  measuring  about  an  inch  and  a half 
in  length,  which  extends  from  the  inner  end  of  the  ovary  to  the  upper 
angle  of  the  uterus,  immediately  behind  and  below  the  point  of  attach- 
ment of  the  Fallopian  tube;  it  causes  a slight  elevation  of  the  posterior 
layer  of  the  serous  membrane,  and,  together  with  the  ovary  itself, 
forms  the  lower  limit  of  a triangular  portion  of  the  broad  ligament, 
which  has  been  named  the  ala  vespertilionis  or  bat’s  wing  (r). 

The  round  ligaments  are  two  cord-like  bundles  of  fibres,  about  four 
or  five  inches  in  length,  attached  to  the  upper  angles  of  the  uterus,  one 
on  either  side  (ligamentum  rotundum,  lig.  teres  uteri ; fig.  492,  n,  n), 
immediately  in  front  of  the  Fallopian  tube.  From  this  point  each 
ligament  proceeds  upwards,  outwards,  and  forwards,  to  gain  the 
internal  inguinal  ring;  and  after  having  passed,  like  the  spermatic 
cord  in  the  male,  through  the  inguinal  canal,  reaches  the  fore  part  of 
the  pubic  symphysis,  where  its  fibres  expand  and  become  united  with 
the  substance  of  the  mons  veneris.  Besides  cellular  tissue  and  vessels, 
the  round  ligaments  contain  plain  muscular  fibres,  like  those  of  the 
uterus,  from  which,  indeed,  they  are  prolonged.  Each  ligament  also 
receives  a covering  from  the  peritoneum,  which,  in  the  young  subject, 
is  prolonged  under  the  form  of  a tubular  process  for  some  distance 
along  the  inguinal  canal;  this,  which  resembles  the  vaginiform  process 
of  peritoneum  originally  existing  in  the  same  situation  in  the  male,  is 
named  the  canal  of  Nuck:  it  is  generally  obliterated  afterwards,  but  is 
sometimes  found  even  in  advanced  life. 

Blood-vessels  and  nerves. — The  arteries  of  the  uterus  are  four  in 
number,  viz.,  the  right  and  left  ovarian  (which  correspond  to  the 
spermatic  of  the  male)  and  the  two  uterine.  Their  origin,  as  well  as 
the  mode  in  which  they  reach  the  uterus  and  ovaries,  has  been  already 
described  (vol.  i.  pp.  603,  611).  They  are  remarkable  for  their  frequent 
anastomoses,  and  also  for  their  singularly  toriuous  course:  within  the 
substance  of  the  uterus  they  seem  to  be  placed  in  little  channels  or 
canals.  The  veins  correspond  with  the  arteries : they  are  very  large 
and  form  the  uterine  plexuses,  and  their  thin  walls  are  in  immediate 
contact  with  the  uterine  tissue.  The  course  of  the  lymphatics  is 
described  in  vol.  ii.  p.  5 1 ; they  are  very  large  and  abundant  in  the  gravid 
uterus.  The  nerves  have  been  fully  described  (p.  356).  They  are 
derived  from  the  inferior  hypogastric  plexuses,  the  spermatic  plexuses, 
and  the  third  and  fourth  sacral  nerves. 

The  changes  which  take  place  in  the  \derus  from  age,  menstruation,  and  gestation, 
and  the  characters  presented  by  this  organ  after  it  has  once  performed  the  latter 
function,  can  only  be  very  generally  indicated  here. 

For  some  time  after  menstruation  first  commences,  the  uterus  becomes  rounder 
and  slightly  enlarged  at  each  period,  its  os  externum  becomes  more  rounded,  and 
its  lips  swollen : subsequently  these  periodical  alterations  are  not  so  marked.  The 
organ  itself,  however,  always  becomes  more  turgid  with  blood,  and  the  mucous 
membrane  appears  darker,  softened,  and  thickened. 

In  gestation  more  extensive  alterations  ensue,  which  necessarily  affect  the  size, 


564 


THE  OVARIES. 


shape,  and  position  of  the  organ,  the  thickness  and  amount  of  substance  in  its 
walls,  the  dimensions  and  form  of  its  cavity,  and  the  character  of  its  cervix  and 
of  its  os  externum  and  os  internum.  Its  weight  increases  from  about  one  ounce 
to  one  pound  and  a half  or  even  three  pounds.  Its  colour  becomes  ^darker,  its 
tissue  less  dense,  its  muscular  bundles  more  evident,  and  their  fibres  more  cha- 
racteristic. The  round  ligaments  become  enlarged,  and  their  muscular  structure 
more  marked ; the  broad  ligaments  are  encroached  upon  by  the  intrusion  of  the 
growing  utems  between  their  layers.  The  mucous  membrane  and  the  glands  of 
the  body  of  the  uterus  become  the  seat  of  singular  changes,  which  lead  to  the 
formation  of  the  decidual  membrane ; whilst  that  of  the  cervix  loses  its  columns 
and  rugae.  The  blood-vessels  and  lymphatics  are  greatly  enlarged,  and  it  is 
observed  that  the  arteries  become  exceedingly  tortuous,  as  they  ramify  upon  the 
organ.  The  condition  of  the  nerves  in  the  gravid  uterus  has  been  already  dis- 
cussed (p.  356). 

After  parturition,  the  uterus  again  diminishes,  but  never  regains  its  original 
virgin  character.  Its  weight  usually  remains  about  two  or  three  ounces  in  those 
who  have  had  children ; its  cavity  is  larger ; the  os  externum  is  more  rounded, 
and  its  margins  often  puckered  or  fissured;  the  arteries  continue  much  more 
tortuous  than  they  are  in  the  virgin;  and  its  muscular  fibres  and  layers  remain 
more  defined. 

Age. — In  the  infant  the  neck  of  the  uterus  is  larger  than  the  body ; and  the 
fundus  is  not  distinguished  either  by  its  breadth  or  its  convex  outline.  These 
parts  afterwards  enlarge  gradually,  until,  at  puberty,  the  pyriform  figure  of  the 
womb  is  fully  established.  The  arbor  vitae  is  very  distinct,  and  indeed  at  first 
reaches  upwards  to  the  highest  part  of  the  cavity. 

From  the  gradual  effects  of  age  alone,  independent  of  impregnation,  the  uterus 
slrrinks,  and  becomes  paler  in  colour,  and  harder  in  texture ; its  triangular  form  is 
lost;  the  body  and  neck  become  less  distinguishable  from  each  other;  the  orifices 
also  become  less  characteristic. 

THE  OVARIES  AND  FALLOPIAN  TUBES. 

The  ovaries  (fig.  493,  o,  o),  the  parts  analogous  to  the  testicles  of  the 
male  (ovaria,  testes  muliebres),  are  two  somewhat  flattened  oval 
bndies,  which  are  placed  one  on  each  side,  nearly  horizontally,  at  the 
back  of  the  broad  ligament  of  the  uterus,  and  are  enveloped  by  its 
posterior  membranous  layer.  The  ovaries  are  largest  in  the  virgin 
state;  their  weight  is  from  three  to  five  scruples,  and  they  usually 
measure  about  one  inch  and  a half  in  length,  three  quarters  of  an  inch 
in  width,  and  nearly  half  an  inch  in  thickness;  but  their  size  is  rather 
variable.  Each  ovary  is  free  on  its  two  sides,  and  also  along  its 
posterior  border,  which  has  a convex  outline;  but  it  is  attached  along 
its  anterior  border,  which  is  straighter  than  the  other,  and  by  which 
alone  the  vessels  and  nerves  reach  it.  Its  inner  end  is  generally 
narrow,  and  is  attached  to  the  dense  cord  already  described  as  the 
ligament  of  the  ovary  {p),  by  which  it  is  connected  with  the  uterus. 
Its  outer  extremity  is  more  obtuse  and  rounded,  and  has  attached  to  it 
one  of  the  fimbriae  of  the  Fallopian  tube  (s). 

Structure. — The  colour  of  the  ovaries  is  whitish,  and  their  surface 
is  either  smooth,  or  more  commonly  irregular,  and  often  marked  with 
pits  or  clefts  resembling  scars.  Beneath  the  peritoneal  coat,  which 
covers  it  everywhere  except  along  its  attached  border,  the  ovary  is 
enclo.sed  in  a proper  fibrous  coat  (tunica  albuginea),  of  a whitish  aspect 
and  of  considerable  thickness,  which  adheres  firmly  to  the  tissue 
beneath.  When 'this  latter  is  divided,  it  is  seen  to  consist  of  a firm 
reddish-white  vascular  structure  called  the  stroma  (fig.  494  a,*),  in 


THE  FALLOPIAN  TUBES. 


565 


which  are  lodged  a number  of  small  vesicles  of  various  sizes,  named 
the  Graafian  vesicles  or  follicles  (vesiculte  Graafianse).  In  females 


Fig.  494. 


A.  Graafian  vesicle  of  a mammal  seated  in  the  ovary,  magnified  : — (Baer). — 1.  Vascular  stroma 
of  the  ovary.  2.  Peritoneal  coat  of  ovary.  3.  Outer,  and  4,  inner  tunics  of  Graafian  vesicle, 
o.  Membrana  granulosa  of  Baer.  6.  Fluid  in  cavity  of  vesicle.  7.  Granular  disc  of  Baer.  8. 
The  ovum. 

B.  Ovum  of  the  sow,  removed  from  the  Graafian  vesicle,  and  lying  amongst  granular  matter. 
Magnified  highly. — (Barry.) — 1.  Germinal  spot  of  Wagner.  2.  Germinal  vesicle  of  Purkinje.  3. 
The  yolk.  4.  The  transparent  tunic  of  ovum.  5.  Tunica  granulosa  (Barry);  granular  disc 
(Baer).  6.  Adherent  granules. 

who  have  not  had  children  there  are  usually  from  eight  to  fifteen  or 
twenty  of  these  vesicles  in  each  ovary,  varying  from  the  size  of  a 
pin’s  head  to  that  of  a pea.  As  many  as  thirty,  and  even  fifty  have 
been  counted.  They  are  filled  with  a clear,  colourless,  albuminous 
fluid  (*’),  and  the  larger  ones  approach  the  surface  of  the  ovary,  on 
which  they  may  sometimes  be  distinguished  as  semitransparent  eleva- 
tions. These  vesicles  are  not  the  ova,  as  was  formerly  supposed,  but 
each  includes,  besides  its  fluid  contents,  a small  round  vesicular  body, 
first  distinctly  pointed  out  by  Baer,  which  is  the  true  ovum  (*). 
Sometimes,  though  rarely,  two  ova  have  been  found  in  one  vesicle. 

The  vesicles  of  De  Graaf  have  two  coals,  viz.,  an  external  vascular 
tunic  (®)  and  an  internal  tunic,  named  the  ovi-capsule  (^),  which  is  lined 
with  a granular'epithelial  layer,  the  membrana  granulosa  (®).  At  first 
the  ovule  appears  to  be  floating  near  the  centre  of  the  vesicle,  but,  in 
the  mature  condition  of  the  latter,  it  approaches  the  internal  surface 
of  the  ovi-capsule,  and  becomes  embedded  in  a small  flattened  heap  of 
granular  substance  (^),  which  there  forms  part  of  the  membrana 
granulosa.  By  rupture  of  the  vesicle  the  ovum  escapes  into  the  Fal- 
lopian tube,  and  is  thus  conveyed  into  the  womb,  while  the  ruptured 
vesicle  becomes  converged  into  a yellow  mass,  named  a corpus  luteum, 
which,  after  persisting  for  a time,  dwindles  down  into  a small  fibrous 
cicatrix. 

The  ovum  itself  (fig.  494,  a,®  and  b,)  is  a perfectly  spherical  body,  very  constant 
in  size,  being  about  yvnth  of  an  inch  in  diameter;  it  consists  of  a thick,  colourless, 
and  transparent  envelope,  (zona  pellucida,  Baer;  membrana  pellucida)  (■*),  which 
surrounds  the  substance  of  the  yolk.  Within  the  yOlk  (®),  which  is  made  up  of 
granular  matter,^  is  situated  a still  smaller  vesicular  body,  named  the  germinal 
vesicle  (“),  which  is  about  T^jjth  of  an  inch  in  diameter;  and  in  this  again  is  an 
opaque  spot,  having  a diameter  only  of  3^^^  to  3300^^  of  ail  inch,  and  named  the 
germinal  spot  (macula  germinativa)  ('). 

The  Fallopian  tubes  (figs.  492,  493,  s,  s). — These  tubes  (tubas  Fal- 
lopianse  uterinae),  which  may  be  considered  as  ducts  of  the  ovaries, 

VOL.  II.  48 


566 


THE  FALLOPIAN  TUBES. 


and  which  serve  to  convey  the  ovum  from  thence  into  the  uterus,  are 
inclosed  in  the  free  margin  of  the  broad  ligaments.  They  are  between 
three  and  four  inches  in  length.  Their  inner  or  attached  extremity, 
which  proceeds  from  the  upper  angle  of  the  uterus,  is  narrow  and 
cord-like;  but  from  this  point  they  soon  begin  to  enlarge,  and  pro- 
ceeding outwards,  one  on  each  side,  pursue  an  undulatory  course,  and 
at  length,  having  become  gradually  wider,  they  bend  backwards  and 
downwards  towards  the  ovary,  about  an  inch  beyond  which  they 
terminate  in  an  expanded  extremity,  the  margin  of  which  is  divided 
deeply  into  a number  of  irregular  processes  named  fimbria,  of  which 
one,  somewhat  longer  than  the  rest,  is  attached  to  the  outer  end  of 
the  corresponding  ovary.  This  wide  and  fringed  end  of  the  Fallopian 
tube,  or  rather  trumpet,  as  the  term  “ tuba”  literally  signifies,  is  turned 
forwards,  and  is  named  the  fimbriated  extremity  (morsus  diaboli,  t t). 
In  the  midst  of  these  fimbriae,  which  are  arranged  in  a circle,  the  tube 
itself  opens  by  a round  constricted  orifice,  ostium  abdominale  (fig.  492, 
u),  placed  at  the  bottom  of  a sort  of  fissure  leading  from  that  fringe 
which  is  attached  to  the  ovary.  It  is  by  this  orifice  that  an  ovum  is 
received  at  the  time  of  its  liberation  from  the  ovary,  and  is  thence 
conveyed  along  the  uterine  extremity  of  the  tube,  which  opens  into 
the  womb  by  a very  minute  orifice,  scarcely  admitting  a fine  bristle, 
and  named  ostium  uterinum  (fig.  493,  i).  The  part  of  the  canal  w'hich 
is  near  the  uterus  is  also  very  fine,  but  it  becomes  gradually  larger  to 
its  abdominal  orifice,  where  it  is  again  somewhat  contracted. 

Beneath  the  external  or  peritoneal  coat  the  walls  of  the  tube  contain, 
besides  cellular  tissue,  plain  muscular  fibres  like  those  of  the  uterus, 
arranged  in  an  external  longitudinal,  and  an  internal  circular  layer. 
The  mucous  membrane  lining  the  tubes  is  thrown  into  longitudinal 
plicae,  which  are  broad  and  numerous  in  the  wider  part  of  the  tube; 
it  is  continuous,  on  the  one  hand,  with  the  lining  membrane  of  the 
uterus,  and  at  the  outer  end  of  the  tube  with  the  peritoneum,  presenting 
an  example  of  the  direct  continuity  of  a mucous  and  serous  membrane, 
and  making  the  peritoneal  cavity  in  the  female  an  exception  to  the 
ordinary  rule  of  serous  cavities,  i.  e.,  of  being  perfectly  closed.  The 
epithelium  in  the  interior  of  the  Fallopian  tube  is,  like  that  in  the 
uterus,  columnar  and  ciliated;  the  inner  surface  of  the  fimbriae  is  also 
provided  with  cilia,  and  Henle  has  even  detected  ciliated  epithelium 
on  their  outer  or  serous  surface,  but  it  here  soon  passes  into  the  scaly 
epithelium  of  the  peritoneal  membrane.  » 

Vessels  and  nerves  of  the  ovaries  and  Fallopian  tubes. — The  ovaries 
are  supplied  by  the  ovarian  arteries,  analogous  to  the  spermatic  in  the 
male  (vol.  i.  p.  603),  which  anastomose  freely  by  an  internal  branch 
with  the  termination  of  the  uterine  arteries  (p.  611).  Sometimes  this 
anastomotic  branch  is  so  large  that  the  ovary  seems  to  be  supplied 
almost  entirely  by  the  uterine  artery.  It  always  sends  numerous 
branches  to  the  Fallopian  tube.  The  arteries  penetrate  the  ovary 
along  its  attached  border,  pierce  the  proper  coat,  and  run  in  flexuous 
parallel  lines  through  its  substance.  The  veins  correspond,  and  the 
ovarian  veins  form  a plexus  near  the  ovary,  named  the  pampiniform 
plexus  (vol.  ii.  p.  29).  The  nerves  are  derived  from  the  spermatic  or 


DEVELOPMENT  OF  URINARY  ORGANS. 


567 


ovarian  plexus ; and  also  from  one  of  the  uterine  nerves,  which 
invariably  send  an  offset  to  the  Fallopian  tube  (p.  356.) 


Genito-urinary  organs  of  a 


DEVELOPMENT  OF  THE  GENITO-DRINARY  ORGANS. 

The  Urinary  Organs. 

The  Wolffian  Bodies  and  their  Excretory  Ducts. — The  development  of  the  genito- 
urinary organs  in  reptiles,  birds,  and  mammalia,  including  man,  is  preceded  by 
the  formation  of  two  tempcrrary  glands,  named,  after  C.  F.  Wolff,  the  Wolffian 
bodies.  In  the  embryos  of  the  higher  mammalia  these  organs  are  proportionally 
smaller,  and  disappear  earlier  than  in  those  of  the 
lower  mammalia,  birds,  or  reptiles.  In  the  human 
subject,  accordingly,  the  Wolffian  bodies  (fig.  495, ■*) 
are  relatively  small,  and  arb  found  only  in  v^ery  early 
fcBtuses.  In  the  mammalian  embryo,  at  a period  when 
the  intestinal  canal  still  communicates  with  the  umbi- 
lical vesicle,  the  Wolffian  bodies  commence  in  the 
form  of  two  slight  ridges  of  blastema,  placed  one  on 
each  side  of  the  line  of  attachment  of  the  intestine  to 
the  vertebral  column.  On  reaching  their  full  size, 
which  in  man  seems  to  be  about  the  fifth  week  of 
embryonic  life,  they  have  the  appearance  of  two 
oblong  reddish  masses,  placed  on  the  sides  of  the 
vertebral  column  and  extending  from  the  lower  end  of 
the  abdomen  to  the  vicinity  of  the  heart.  Their  struc- 
ture is  decidedly  glandular;  clear  pedunculated  vesicles  human  embryo’ eight  lines  m 
may  be  early  discovered  in  them,  opening  into  an  length,  magnified  (Muller)  1. 
excretory  duct,  which  runs  along  the  outer  side  of  Supra-renai  capsule  of  right 
each  organ.  These  vesicles  subsequently  become  ris''’ondnr^  kidrm 2^^  Left 
lengthened  into  transverse  and  somewhat  tortuous  h^h^,ey  and  u re ler.'^ex posed  by 
coBcal  tubes,  which  open  in  like  manner  into  the  removal  of  the  left  supra-renai 
common  duct.  The  Wolfffan  bodies  are  highly  capsule.  3,  Right  testis  or 
vascular,  their  larger  blood-vessels  running  between  ‘’''^Lv-  4.  Wolffian  body.  5. 
and  parallel  with  the  transverse  tubules.  In  the  efe.ens  or  Fallopian  tube, 
embryo  of  the  coluber  natrix,  Rathke  has  observed  little  vascular  tufts,  which  he 
compares  to  the  Malpighian  corpuscles  of  the  kidneys. 

As  to  the  xxcretory  duct,  Muller  is  of  opinion,  that  in  mammalia,  it  emanates 
from  the  lower  end  of  the  Wolffian  body,  but  others  agree  in  stating,  that,  as  in 
birds,  it  lies  along  the  outer  border  of  the  gland,  receiving  the  tubules  in  its 
course.  The  ducts  of  the  two  bodies  open  into  the  sac  of  the  allantois,  to  be  pre- 
sently described. 

A whitish  secretion  has  been  seen  in  the  ducts  of  the  Wolffian  bodies  of  birds 
and  serpents  resembling  the  urine  of  those  animals,  and  since,  also,  the  fluid  of 
the  allantois  has  been  found  to  contain  uric  acid,  it  is  thought  that  the  Wolffian 
bodies  perform  the  office  of  kidneys  during  the  early  part  of  foetal  life.  They  are 
accordingly  sometimes  named  the  primitive  or  pimordial  kidneys. 

As  development  advances,  the  Wolffian  bodies  (■•)  rapidly  become  shorter  and 
thicker  in  proportion;  they  shrink  towards  the  lower  part  of  the  abdominal 
cavity,  and  soon  become  almost  entirely  wasted.  By  the  end  of  the  second 
month  scarcely  any  trace  of  them  is  visible  in  the  human  embryo.  They  take 
no  part  in  the  formation  of  the  kidneys  (°)  or  suprarenal  capsules  (‘),  nor  in  that 
of  the  ovaries  or  body  of  the  testis  (®).  Remnants  of  the  tubular  structure  of 
these  temporary  organs  are,  however,  to  be  found  in  female  embryos,  situated  in 
the  fold  of  peritoneum,  connecting  the  ovary  wdth  the  Fallopian  tube  (fig.  496, 
c,^).  Similar  appearances  of  tubuli,  with  rounded  corpuscles  intermixed,  are  met 
with  in  the  same' situation,  at  later  periods  of  intra-uterine  life,  and  even  for 
some  time  after  birth,  constituting  what  is  named  the  (xrgan  of  RosenmUller,  a 
structure  which  J.  F.  Meckel  regarded  as  an  abortive  or  rudimentary  epididymis. 
Kobelt  maintains  that  a remnant  of  the  Wolffian  body  persists  throughout  life, 
forming  in  the  adult  female  an  appendage  to  the  ovary  {Neben-Eyerstock)  analogous 


568 


DEVELOPMENT  OF  URINARY  ORGANS. 


to  the  epididymis  of  the  male.  It  is,  moreover,  supposed  by  Kathke,  that,  in  the 
male,  the  middle  tubuli  of  each  Wolffian  body,  together  with  its  excretory  duct, 
become  converted  into  the  epididymis  and  vas  deferens  of  the  corresponding 
side ; and  Kobelt  has  adopted  a similar  view  as  to  the  origin  of  the  epididymis. 
Lastly,  it  has  been  held  by  Muller,  that  in  mammalia  the  lower  portion  of  the 
excretory  duct  of  the  Wolffian  body  persists  as  part  of  the  corresponding  Fallopian 
tube  or  vas  deferens. 

The  Kidneys  and  Ureters. — The  kidneys  commence  subsequently  to  and  inde- 
pendently of  the  Wolffian  bodies.  They  lirst  appear,  it  is  said,  about  the  seventh 
week,  as  tw’o  small  dark  oval  masses,  situated  behind  the  upper  part  of  the 
Wolffian  bodies,  which  are  still  large,  and  completely  hide  the  kidneys.  Though 
at  lirst  smooth  and  oval  (fig.  495,°),  the  kidneys  soon  assume  their  character- 
istic general  outline,  and  about  the  tenth  week  are  distinctly  lobulated  (fig.  496, 
A,°).  The  separate  lobules,  generally  about  fifteen  in  number,  gradually  coalesce 
in  the  manner  already  described  (p.  509);  but  at  birth,  indications  of  the  original 
lobulated  condition  of  the  kidney  are  still  visible  on  the  surface,  and  the  entire 
organ  is  more  round  in  its  general  figure  than  in  the  adult.  The  kidneys  are  then 
also  situated  lower  down  than  in  after  life. 

The  formative  blastema  of  the  kidney,  as  observed  by  Rathke  in  the  fcetal 
calf,  soon  contains  a series  of  club-shaped  bodies  which  have  their  larger  ends 
free  and  turned  outwards,  and  their  smaller  ends  or  pedicles  directed  inwards 
towards  the  future  hilus,  where  they  are  blended  together.  As  the  organ  grows 
these  bodies  increase  in  number,  and  finally,  becoming  hollow,  form  the  urini- 
ferous  tubes.  At  first,  short,  wide,  and  dilated  at  their  extremities,  the  tubuli  soon 
become  elongated,  narrow,  and  flexuous,  occupying  the  whole  mass  of  the 
kidney,  which  then  appears  to  consist  of  cortical  substance  only.  At  a subse- 
quent period,  the  tubuli  nfearest  the  hilus  become  straighter,  and  thus  form  the 
medullary  substance.  The  tubuli,  as  shown  by  Valentin,  are  absolutely,  as  well 
as  relatively,  wider  in  an  early  condition  of  the  kidney.  The  Malpighian  cor- 
puscles have  been  seen  by  Rathke  in  a sheep’s  embryo,  the  kidneys  of  which 
measured  only  two  and  a half  lines  in  length. 

The  ureters,  it  is  stated  by  Rathke,  commence  after  the  kidneys,  and  then 
become  connected  with  the  hilus  of  each  organ,  and  with  the  narrow  ends  of  the 
club-shaped  bodies  in  its  interior.  At  first  the  growing  tubuli  do  not  seem  to 
communicate  with  the  cavity  of  the  ureter ; but  subsequently,  when  the  wide 
upper  portion  of  this  canal  or  pelvis  of  the  kidney  has  become  divided  to  form  the 
future  calices,  the  pencil-like  bundles  of  the  tubuli  open  into  each  subdivision  of 
the  ureter,  and  give  rise  at  a later  period  to  the  appearance  of  the  papillce  and 
their  numerous  orifices.  The  lower  ends  of  the  ureters  soon  come  to  open  into 
that  part  of  the  sac  of  the  allantois,  which  afterwards  becomes  converted  into  the 
bladder.  The  researches  of  Muller,  Valentin,  and  Bischoff  are  in  general  con- 
firmatory of  Rathke’s  account;  Valentin,  however,  believes  that  the  ureter  (which 
he  has  seen  at  the  earliest  periods),  the  pelvis  of  the  kidney,  and  the  uriniferous 
tubules  are  formed  in  a general  blastema,  independently  of  one  another;  and 
that,  each  part  first  becoming  separately  hollowed  out,  their  cavities  afterwards 
communicate  with  each  other.  Bischoff  states  that  the  ureters  appear  at  the  same 
time  as  the  kidneys,  and  are  formed  in  continuity  with  the  uriniferous  tubules, 
and  moreover  that  all  these  jrarts,  which  are  at  first  solid,  are  excavated,  not 
separately  but  in  common,  in  the  further  progress  of  development.- 

In  the  advanced  foetus  and  in  the  new-born  infant,  the  kidneys  are  relatively 
larger  than  in  the  adult,  the  weight  of  both  glands  compared  with  that  of  the 
body,  being,  according  to  Meckel,  about  one  to  eighty  at  birth. 

The  Suprarenal  Capsules. — Arnold  alone  has  supposed  that  these  organs  are 
formed  from  a part  of  the  Wolffian  bodies  severed  from  the  rest.  Mr.  Goodsir  is 
of  opinion  that  they  are  remnants  of  the  primitive  blastodermic  membrane. 
Other  observers  attribute  to  these  organs  an  independent  origin.  Valentin  describes 
them  as  originating  in  a single  mass,  placed  in  front  of  the  kidneys,  and  after- 
wards becoming  divided.  Meckel  has  also  seen  them  partially  blended  together. 
Muller  has  found  the  Suprarenal  capsules  in  contact,  but  uot  united.  Bischoff 
has  always  seen  them  separate,  and  in  early  conditions  closely  applied  to  the 
upper  end  of  the  Wolffian  bodies. 


DEVELOPMENT  OF  URINARY  ORGANS. 


5B9 


In  quadrupeds,  the  suprarenal  capsules  are  at  all  times  smaller  than  the 
kidneys;  but  in  the  human  embryo  (figs.  495,  496,  a,‘)  they  are  for  a time  larger 
than  those  organs,  and  quite  conceal  them.  At  about  the  tenth  or  twelfth  week, 
the  renal  capsules  are  smaller  than  the  kidneys;  at  birth  the  proportion  between 
them  is  1 to  3,  whilst  in  the  adult  it  is  about  1 to  22.  They  diminish  in  aged 
persons. 

T/ie  Allantois,  Urinary  Bladder,  and  Urachus. — The  name  of  Allantois  was  ori- 
ginally given  to  a membranous  sac  which  is  appended  to  the  umbilicus  of  various 
quadrupeds  in  the  fcetal  state,  and  which  communicates  with  the  urinary  bladder 
by  means  of  a canal  passing  through  the  umbilical  aperture  and  named  the 
urachus.  These  several  parts  are  formed  out  of  one  original  saccular  process, 
which  passes  out  from  the  cloacal  termination  of  the  intestine,  and  which  sub.se- 
quently  becomes  distinguished  into  the  bladder,  the  urachus  and  the  allantois 
strictly  so  called ; and  modern  embryologists  employ  the  term  allantois  also  to  signify 
the  original  common  representative  of  the  different  parts  referred  to.  In  this  sense 
an  allantois  may  be  said  to  exist  not  only  in  mammalia,  but  also  in  birds  and 
reptiles,  subject,  however,  to  great  differences  in  its  subsequent  development  and 
relative  importance.  Thus  in  Batrachians  it  does  not  extend  out  of  the  body  at 
all;  in  scaly  reptiles,  on  the  other  hand,  as  well  as  in  birds  and  in  some  quad- 
rupeds, it  ultimately  surrounds  the  body  of  the  fcetus  and  spreads  itself  over  the 
inner  surface  of  the  chorion;  whilst  in  other  quadrupeds  its  e.xtra-abdominal 
portion  is  of  small  extent.  In  man  the  allantois  proper  is  not  only  very  insignifi- 
cant in  point  of  size,  but  also  extremely  limited  in  duration,  for  it  vanishes  at  a 
very  early  period  in  the  life  of  the  embryo ; and  whdst  in  many  animals  it  serves 
both  as  a receptacle  for  the  secretion  of  the  fcetal  urinary  organs,  and  as  a vehicle 
to  conduct  the  umbilical  vessels  from  the  body  of  the  embryo  to  the  chorion  to 
form  the  placenta  (or  some  equivalent  vascular  structure),  it  seems  in  the  human 
species  to  serve  merely  for  the  latter  purpose.  The  allantoid  process  communi- 
cates below  with  the  intestinal  canal,  and  receives  the  wide  excretory  ducts  of 
the  Wolffian  bodies,  the  ureters,  and  the  Fallopian  tubes  or  vasa  deferentia.  By 
Baer,  Rathke,  and  others,  the  allantois  has  been  regarded  as  formed  from  the 
intestinal  tube,  and  by  Reichert  as  developed  upon  the  excretory  ducts  of  the 
Wolffian  bodies.  Bischoff  says  that,  in  the  embryos  of  the  rabbit  and  dog,  it 
commences  before  the  appearance  of  either  the  W olffian  bodies  or  the  intestuie, 
as  a solid  mass  projecting  forwards  from  the  posterior  extremity  of  the  body. 
This  mass  soon  becomes  hollowed  into  a vesicle,  which  is  covered  with  blood- 
vessels, and  communicates  with  the  intestine.  Continuing  rapidly  to  enlarge,  it 
protrudes  between  the  visceral  plates,  and,  when  these  close  together,  through  the 
opening  of  the  umbilicus,  forming  in  the  rabbit  a pear-shaped  sac,  which  conveys 
blood-vessels  (soon  recognised  as  the  umbilical  vessels)  to  the  chorion  to  form 
the  foetal  part  of  the  placenta. 

In  the  human  embryo,  the  portion  of  the  allantois  situated  beyond  the  umbilicus 
disappears  entirely  at  a very  early  period,  and  the  internal  portion,  reaching  from 
the  umbilicus  to  the  intestine,  is  first  elongated,  and  then  becomes  widened  below 
to  form  the  bladder,  whilst  its  upper  part  shrinks,  and  is  at  length  completely 
closed  to  form  the  urachus;  but,  even  up  to  the  period  of  birth,  the  urachus  often 
remains  tubular  for  a certain  distance  above  the  bladder.  The  account  of  the 
metamorphosis  of  the  allantois  given  recently  by  Dr.  M.  Langenbeck  is  some- 
what different.  That  observer  states  that  the  wide  part  of  the  allantois,  originally 
outside  the  body  of  the  embryo,  is  not  obliterated,  but  is  drawn  into  the  abdominal 
cavity,  its  remote  portion  having  previously  become  constricted  to  form  the  future 
urachus,  whilst  the  part  nearest  the  embryo,  together  with  the  narrow  portion 
already  within  the  fcetus,  is  destined  to  form  the  bladder. 

The  lower  part  of  the  allantois,  or  rudimentary  bladder,  receiving  as  already 
mentioned  the  efferent  canals  of  the  Wolffian  bodies,  as  well  as  those  of  the 
kidneys  and  of  the  ovaries  or  testes,  at  first  communicates  freely  with  the  lower 
end  of  the  intestinal  tube,  and  when  this  becomes  opened  to  the  exterior,  there  is 
formed  a sort  of  cloaca,  as  in  adult  birds  and  reptiles.  Soon,  however,  a separa- 
tion takes  place,  and  the  genito-urinary  organs  have  a distinct  passage  to  the 
exterior,  named  the  sirms  uro- genitalis,  (fig.  496,  b ,)  situated  in  front  of  the  termi- 
nation of  the  intestine. 


48* 


570 


DEVELOPMENT  OF  GENERATIVE  ORGANS. 


The  Organs  of  Generation. 

The  development  of  the  parts  concerned  in  the  reproductive  function  does  not 
begin  until  after  the  rudiments  of  the  principal  organs  of  the  body  have  appeared. 
The  internal  organs  of  generation  first  commence,  and  for  a brief  period  no  sexual 
difference  is  perceptible  in  them.  The  external  organs,  which  subsequently  begin 
to  be  formed,  are  also  identical  in  appearance,  in  the  two  sexes,  as  late  as  the 
fourteenth  week. 

The  Internal  Organs  of  Generation.  The  Ovaries  and  Testes. — The  rudiments  of 
the  ovaries  or  testes,  for  it  cannot  at  first  be  determined  which  are  ultimately  to  be 
produced,  appear  after  the  formation  of  the  allantois  and  Wolffian  bodies,  but  a 
little  sooner  than  the  kidneys.  They  consist  of  two  small  whitish  oval  masses  of 
blastema  (fig.  495,“),  placed  on  the  inner  border  of  the  Wolffian  bodies.  The 
earliest  peculiarities  of  se.x  which  are  distinguishable,  occur  in  the  form,  position, 
atrd  structure  of  these  rudiments  of  the  essential  reproductive  organs.  The 
ovaries,  for  example,  become  elongated  and  flattened,  and  soon  assume  first  an 
oblique  and  then  a nearly  transverse  position  (fig.  496,  a,“)  : the  testes,  on  the 

Fig.  496. 


Genito-urinary  organs  of  a female  embryo,  measuring  three  inches  and  a half  in  length.  (Muller.) 
A.  General  view.  1.  Left  supra-renal  capsule.  2.  Left  kidney.  3.  Right  ovary.  4,  Left  Fal- 
lopian tube.  5.  Uterus.  6.  intestine.  7.  Bladder.  B.  Genito-urinary  organs  viewed  from  one 
side  and  enlarged.  1.  Bladder.  2.  -Urethra.  3.  Uterus,  bifid.  4.  Vagina.  5.  Part  common  to 
the  vagina  and  urethra,  or  sinus  urelhro-genitalis.  6.  Common  orifice  of  the  urethra  and  genital 
organs.  7.  Clitoris,  c.  Internal  organ,  still  further  magnified.  1.  Uterus,  bifid,  or  with  the  fun- 
dus notched.  2.  Round  ligament.  3.  Fallopian  tube.  4.  Ovaries.  5.  Remains  of  Wolffian  bodies. 
D.  External  parts,  also  magnified.  1.  Labia  majora.  2.  Nymphae,  leading  down  from  the  under 
side  of  the  clitoris.  3.  Gians  clitoridis. 

Other  hand,  become  rounder  and  thicker,  and  retain  their  nearly  vertical  direction. 
Moreover,  as  development  advances,  the  ovaries  remain  Unconnected  with  the 
Fallopian  tubes,  whilst  the  testes  become  united  with  the  corresponding  excre- 
tory canals  or  vasa  deferentia.  Lastly,  though  both  ovaries  and  testicles  gradually 
change  their  original  position,  and  become  situated  lower  down  than  at  first,  the 


DEVELOPxMEiNT  OF  GENERATIVE  ORGANS.  571 

former  merely  descend  to  the  pelvic  cavity,  whilst  the  latter  pass  through  the 
inguinal  canal  and  enter  the  scrotum. 

The  changes  which  take  place  in  the  substance  of  the  ovary  and  testis  have 
been  minutely  described  by  Valentin,  who  has  endeavoured  to  trace  the  analogies 
in  the  development  of  each.  Bischoff,  however,  has  not  succeeded  in  confirming 
Valentin’s  description,  and  their  respective  statements  leave  the  subject  yet  in 
doubt.  In  the  human  female,  according  to  Bischotf,  the  Graafian  vesicles  are 
not  usually  visible  in  the  ovarian  stroma  before  birth,  but  exceptions  to  this  rule 
occasionally  occur.  The  ovum  begins  to  form  in  its  Graafian  vesicle,  when  this 
latter  is  still  very  small;  it  soon  nearly  fills  the  vesicle,  which,  however,  grows 
more  rapidly  afterwards,  so  as  at  length  to  acquire  a much  greater  proportionate 
size.  The  development  of  new  Graafian  vesicles  seems  to  continue  as  long  as 
the  procreative  faculty  subsists,  but  beyond  the  age  of  puberty  it  is  difficult  to 
detect  them  in  their  commencing  state. 

The  TubcE  Fallopiana  and  Vasa  drfercntia. — The  mode  of  origin  of  the  Fallopian 
tubes  and  vasa  deferentia  has  been  differently  explained  by  different  inquirers. 
In  the  female  embryo  of  birds,  according  to  Muller,  the  oviduct  (or  Fallopian 
tube)  is  formed  along  the  outer  border  of  the  Wolffian  body,  close  to  but  inde- 
penciently  of  the  duct  of  that  gland ; whereas,  in  the  male  embryo  of  the  bird,  no 
independent  vas  deferens  could  be  detected,  but  the  excretory  duct  of  the  Wolffian 
body  appeared  to  become  connected  by  transverse  vessels  with  the  corresponding 
testicle,  and  to  form  its  vas  deferens.  In  mammalia,  on  the  other  hand,  in  which 
the  excretory  duct  of  the  corpus  Wolffianum  is  described  by  Muller  as  passing 
out  at  its  lower  end,  the  Fallopian  tube,  as  well  as  the  vas  deferens,  is  supposed 
by  that  observer  to  be  formed  out  of  a distinct  canal,  which  has  the  appearance 
of  a filament  running  along  the  outer  border  of  the  Wolffian  body,  and  which 
ultimately  becomes  continuous  below  with  a persistent  portion  of  the  Wolffian 
duct.  In  opposition  to  this  view,  Rathke  maintained  that  both  the  Fallopian 
tubes  and  deferent  vessels  are  formed  altogether  independently  of  the  excretory 
ducts  of  the  Wolffian  bodies,  though  their  rudiments  are  developed  close  to 
those  ducts,  the  situation  of  which  they  ultimately  come  to  occupy.  Rathke  has 
since  been  led  to  adopt  a somewhat  different  opinion : according  to  this  view, 
which  is  founded  on  his  researches  on  the  development  of  the  snake,  but  which 
he  thinks  will  probably  apply  also  to  the  higher  vertebrata,  there  is  formed  along 
the  Wolffian  duct  in  both  sexes,  a solid  filament,  which  is  afterwards  converted 
into  a canal  open  at  its  upper  end.  In  the  female,  the  duct  of  the  Wolffian  body, 
as  well  as  that  body  itself,- is  entirely  absorbed,  whilst  the  new  canal  constitutes 
the  Fallopian  tube;  but,  in  the  male,  the  reverse  takes  place,  the  newly  formed 
canal  disappearing,  and  the  Wolffian  duct  becoming  the  vas  deferens,  whilst 
some  of  the  tubuli  of  the  Wolffian  body  remaining  in  connexion  with  the  duct, 
probably  fcontribute  to  form  the  epididymis.  Bischoff,  after  a careful  examination 
of  these  parts,  declares  that  the  filament  formed  along  the  outer  border  of  each 
Wolffian  body,  contains  not  only  the  excretory  duct  of  that  gland,  but  an  efferent 
sexual  canal,  which  is  the  rudiment  of  the  Fallopian  tube  or  vas  deferens,  and 
that  these  parts  are  both  formed  altogether  independently  of  the  Wolffian  duct. 

In  the  female  embryo,  the  efferent  se.xual  canal  (fig.  495,®)  or  future  Fallopian 
tubcj  becomes  widened,  remains  open  at  its  upper  end,  is  comparatively  short  and 
free  from  convolutions,  and  is  only  slightly  attached  to  the  coinesponding  ovary 
(fig.  496,  A,  c).  In  the  male,  on  the  contrary,  the  efferent  duct,  or  vas  deferens, 
continues  of  comparatively  narrow  calibre,  connects  itself  with  the  testicle,  and 
forms  the  epididymis,  becoming  lengthened  out  and  convoluted.  Muller  also 
thinks  that  no  part  of  the  Wolffian  bodies  is  converted  into  the  generative  organ 
in  either  sex.  He  supposes  that  the  efferent  sexual  tube  or  vas  deferens  becomes 
connected  with  the  testicle  by  means  of  transverse  tubuli  which  do  nat  belong  to 
the  Wolffian  body,  and  that  these  communicating  tubes  form  the  coni  vasculosi, 
whilst  the  rest  of  the  epididymis  is  formed  by  the  convolutions  of  the  efferent 
tube  itself.  It  has  already  been  mentioned  that  Rathke,  and,,  more  recently, 
Kobelt,  are  of  opinion  that  the  junction  of  the  vas  deferens  with  the  testis,  is 
effected  by  means  of  some  of  the  transverse  tubuli  of  the  corresponding  Wolffian 
body  which  persist  and  form  the  epididymis. 

The  descent  of  the  testicles  is  a term  applied  to  the  passage  of  the  te.stes  from  the 


572 


DEVELOPMENT  OF  GENERATIVE  ORGANS. 


abdominal  cavity  into  the  scrotum.  When  yet  situated  at  the  back  of  the  abdomen, 
along  the  inner  border  of  the  Wolffian  bodies,  the  testes  are  covered  in  front  by 
the  peritoneum ; and,  besides  this,  soon  acquire  a proper  envelope,  which  becomes 
the  tunica  albuginea.  At  this  period,  the  blood-vessels  and  nerves,  and,  subse- 
quently, the  efl'erent  apparatus  of  the  gland  or  future  vas  deferens  and  epididymis, 
pass  to  or  from  the  posterior  surface  of  the  testis,  which  is  destitute  of  peritoneal 
covering.  Even  before  the  wasting  of  the  corpora  Wolffiana,  a slight  opaque 
band  or  cord  lying  beneath  the  peritoneum  is  seen  e.xtending  from  the  lower  part 
of  each  of  these  bodies  to  the  inguinal  region.  When  the  Wolffian  bodies  have 
disappeared,  each  testis,  now  increased  in  size,  and  connected  with  its  excretory 
duct,  has  already  moved  somewhat  lower  down  in  the  abdomen  of  the  embryo, 
and  is  supported  by  a suspensory  fold  or  duplicature  of  the  peritoneum,  named 
by  Seiler  the  mesorchium.  By  this  time,  the  opaque  cord  just  mentioned  has 
become  much  larger,  and  reaches  from  the  lower  end  of  the  epididymis  and  testis 
through  the  inguinal  canal  to  the  front  of  the  pubes  and  to  the  scrotum,  consti- 
tuting the  gubernaadum  testis,  so  called  because  it  is  supposed  to  serve  as  a guide 
to  the  testicle  in  its  descent.  At  the  fifth  or  sixth  month  of  fcetal  life,  the  guber- 
naculurn  has  attained  its  full  development ; its  upper  end,  on  which  the  testicle 
rests,  is  broader  than  the  lower  part,  and  lies  in  the  peritoneal  fold  or  mesorchium. 
As  the  testicle  passes  from  the  lumbar  region  to  the  iliac  fossa,  the  gubernaculura 
becomes  shorter,  and  before  the  gland  enters  the  internal  inguinal  ring,  which 
takes  place  in  the  seventh  month,  a small  pouch  of  peritoneum  appears  at  that 
point,  and,  under  the  name  of  the  processus  vaginalis  peritonai,  precedes  the  testicle 
in  its  course  through  the  inguinal  canal,  and  enters  the  scrotum  in  advance  of  the 
gland.  By  the  end  of  the  eighth  month  the  testis  is  in  the  scrotum,  and  a little 
time  before  birth,  the  narrow  neck  of  the  peritoneal  pouch,  by  which  it  previously 
communicated  with  the  general  peritoneal  cavity,  becomes  closed  in  the  manner 
elsewhere  described  (p.  543),  and  the  process  of  peritoneum,  now  entirely  shut 
off  from  the  abdominal  cavity,  remains  as  an  independent  serous  sac,  named  the 
tunica  vaginalis.  It  has  also  been  noticed  elsewhere,  that  some  of  the  lowermost 
fibres  of  the  internal  oblique  muscle,  and  even  of  the  transversalis  muscle  also, 
appear  to  be  carried  down  in  front  of  the  testicle,  to  form  the  cremaster  muscle. 

The  office  of  the  gubernaculum  is  yet  imperfectly  understood.  Hunter,  Cooper, 
Seiler,  and  others,  believed  that  it  contained  muscular  fibres,  which  drew  the 
testicle  into  its  new  position.  Some  have  supposed  that  it  effected  this  by  a slow 
and  gradual  contraction  or  shortening  of  its  tissue ; whilst  a third  opinion  has 
been,  that  it  merely  serves  as  a guide  to  the  path  of  the  gland.  The  muscularity 
of  the  gubernaculura  has  been  denied  by  many  anatomists,  who  regard  this  cord 
as  either  cellular  or  fibrous:  it  often  appears  to  be  partially  hollow.  According 
to  Mr.  Curling,  who  has  recently  examined  it,  it  consists  of  a soft  transparent 
areolar  tissue  within,  and  of  distinct  striped  muscular  fibres  externally.  At  its 
lower  end,  the  gubernaculum  and  these  muscular  fibres  are  arranged  in  three 
bundles,  which  are  connected  respectively  with  Foupart’s  ligament,  the  bottom 
of  the  scrotum,  and  the  pubes : some  fibres,  moreover,  are  derived  from  the 
internal  oblique  muscle.  In  the  opinion  of  Mr.  Curling,  these  muscular  bundles 
aid  in  the  descent  of  the  testicle,  and  afterwards  form  the  cremaster.  According 
to  E.  H.  Weber,  the  gubernaculum  originates  in  form  of  a sac  filled  with  fluid 
and  placed  in  the  situation  of  the  inguinal  canal.  The  lower  end  of  this  sac  is 
protruded  downwards  to  the  bottom  of  the  scrotum : the  upper  end  is  extended 
upwards  through  the  internal  abdominal  ring,  as  high  as  the  testicles,  passing  in 
the  fold  of  peritoneum  by  which  that  organ  is  suspended,  and  carrying  up  along 
with  it  sortie  fibres  from  the  internal  oblique  muscle.  Weber  conceives  that  the 
descent  of  the  testicle  is  effected  by  means  of  an  inversion,  or  as  it  were  an 
intussusception  of  the  hollow  gubernaculum,  which  inversion  commences  at  the 
upper  orifice  of  the  inguinal  canal.*  In  the  female  embryo,  a small  cord,  corre- 
sponding with  the  commencing  gubernaculum  in  the  male,  is  seen  descending  to 
the  inguinal  region,  and  ultimately  becomes  the  round  ligament  of  the  uterus.  It 
is  accompanied  by  a pouch  of  peritoneum  analogous  to  the  processus  vaginalis 
of  the  male,  and  tiamed  the  canal  of  Nuck.  (See  p.  544.) 


* Muller’s  Archiv.,  1847,  p.  403. 


DEVELOPMENT  OF  GENERATIVE  ORGANS. 


573 


Transformation  of  the  uro-genital  sinus.  Formation  of  ihe  female  urethra,  vagina, 
and  uterus,  and  of  the  prostatic  portion  of  the  male  urethra,  the  prostate,  utricidus 
virilis,  and  vesicula  seminales. — After  the  disappearance  of  the  Wolthan  bodies,  the 
sinus  uro- genitalis,  formed  by  the  shutting  off  of  the  lower  part  of  the  allantois  from 
the  tube  of  the  intestine,  receives,  in  either  sex,  only  two  efferent  canals  on  each 
side,  viz.,  the  ureters,  and  the  Fallopian  tubes  or  the  vasa  deferentia. 

In  the  female  emhryo,  this  common  genito-urinary  passage  (fig.  496,  b,^) 
becomes  divided  at  the  bottom  into  an  anterior  part,y>flr«  urinaria,  which  receives 
the  ureters  and  ultimately  forms  the  neck  of  the  bladder  and  the  urethra  if),  and 
a posterior  part,  pars  genitalis,  or  proper  genital  passage,  which  receives  the  Fal- 
lopian tubes  and  represents  the  commencing  vagina  C).  The  urethra  and  vagina 
both  open  into  a still  common  part  or  vestibule  of  the  genito-urinary  passage. 

The  Fallopian  tubes  (fig.  496,  c,®)  coalesce  at  their  lower  ends  so  as  to  form  a 
single  median  cavity,  and  thus  give  rise  to  the  uterus  ('),  or  at  least  to  the  upper 
part  of  that  organ,  for  some  observers  describe  the  lower  part  and  cervix  as  being 
formed  by  the  upper  end  of  the  genital  passage,  or  by  a protrusion  from  it;  the 
lower  part  of  that  passage,  according  to  this  view,  becoming  the  vagina.  For  some 
time  the  uterus  in  the  human  subject  continues  to  be  bifid  or  two-horned,  as  in 
many  quadrupeds,  but,  after  the  end  of  the  third  month,  the  angle  between  the 
orifices  of  the  Fallopian  tubes  begins  to  be  effaced,  and  the  fundus  is  subsequently 
completed.  Sometimes  the  bifid  uterus  continues  through  life.  In  the  latter 
months  of  intra-uterine  e.xistence,  the  cervix  uteri  is  much  larger  in  proportion 
than  the  body  and  fundus,  and,  with  the  os  uteri,  projects  into  the  vagina. 

In  the  male  embryo,  the  urinary  part  of  the  uro-genital  sinus  takes  the  form  of 
a short  canal,  which  represents  the  neck  of  the  bladder  with  the  prostcttic  portion  of 
the  urethra.  The  proper  genital  passage  is  formed,  according  to  Rathke,  by  a 
conical  protrusion  of  the  walls  of  the  common  sinus  at  the  place  where  the 
deferent  ducts  open.  This  observer  supposes  that  the  vesicula.  seminales  begin  as 
two  small  lateral  protrusions  from  the  genital  passage  at  some  distance  apart 
from  the  openings  of  the  vasa  deferentia.  but  that,  by  the  subsequent  shortening 
and  eventual  median  division  of  the  intervening  part  of  the  passage,  each  seminal 
vesicle  comes  at  length  to  open  into  the  urethra  in  conjunction  with  the  deferent 
duct  of  its  own  side.  Bischoff  believes  that  the  so-called  protrusion  is  due  to  an 
increased  thickness  of  the  terminations  of  the  vasa  deferentia,  that  the  vesiculas 
seminales  are  developed,  each  from  its  own  vas  deferens,  and  that  the  thickening 
of  the  lower  ends  of  the  deferent  vessels  has  some  conne.xion  with  the  formation 
of  the  prostate  gland.  The  recent  researches  of  E.  H.  Weber,  elsewhere  referred 
to  (p.  535),  would  seem  to  show  that  the  part  of  the  genital  passage  which  in  the 
female  is  converted  into  the  lower  portion  of  the  uterus,  remaining,  as  it  were,  in 
a rudimentary  condition  in  the  male,  constitutes  the  little  pouch,  named  the  sinus 
pocularis  or  utricidus  virilis,  the  lips  of  which,  as  it  were,  project  into  the  prostatic 
portion  of  the  urethra  and  form  the  verumontanutn. 

The  External  Organs  of  Generation. — As  already  stated,  these  do  not  begin  to 
be  formed  until  after  the  internal  organs,  and,  for  some  time,  they  have  the  same 
form  in  both  sexes. 

Up  to  the  fifth  week,  according  to  Tiedemann,  there  is  no  genito-urinary  orifice, 
and  indeed  no  anus.  About  the  beginning  of  the  sixth  week,  there  is  a common 
opening,  for  the  intestine,  the  generative  and  the  urinary  organs,  i.  e.,  a sort  of 
cloacal  aperture.  In  front  of  this  simple  opening,  there  soon  appears  a small 
recurved  projecting  body,  which,  as  it  enlarges,  becomes  grooved  along  the 
whole  of  its  under  surface.  Tliis  is  the  rudimentary  ch’toj'w  (fig.  496,  d,®)  ov  penis, 
at  the  summit  of  which  an  enlargement  is  formed  which  becomes  the  glans.  The 
margins  of  the  groove  seen  on  its  under  surface  are  continued  backwards  on 
either  side  of  the  common'  aperture,  which  is  now  elliptical,  and  is  bounded 
laterally  by  two  large  cutaneous  folds.  Towards  the  tenth  or  eleventh  week,  a 
transverse  band,  the  commencing  perineum,  divides  the  anal  orifice  from  that  of 
the  genito-urinary  passage,  which  latter  now  appears  as  a rounded  aperture, 
placed  below  the  root  of  the  rudimentaiy  clitoris  or  penis,  and  between  the.  pro- 
longed margins  of  the  groove  beneath  that  organ.  This  opening,  but  not  the 
clitoris  or  penis,  is  concealed  by  the  large  cutaneous  folds  already  mentioned. 
In  this  condition,  which  continues  until  the  fourteenth  week,  the  parts  appear 


574 


MAMMARY  GLANDS 


alike  in  both  sexes,  and  resemble  very  much  the  perfect  female  organs.  The 
rudiments  of  Cou'per’s  glands  are,  it  is  said,  seen  at  an  early  period,  near  the  root 
of  the  rudimentary  clitoris  or  penis,  on  each  side  of  the  genito-urinary  passage. 

In  the  female,  the  two  lateral  cutaneous  folds  enlarge,  so  as  to  cover  the  clitoris 
and  form  the  labia  majora  (fig.  496,  n,').  The  clitoris  itself  becomes  relatively 
smaller,  and  the  groove  on  its  under  surface  less  and  less  marked,  owing  to  the 
opening  out  and  subsequent  extension  backwards  of  its  margins  to  form  the 
nymplue  (“).  The  hymen  begins  to  appear  about  the  fifth  month.  Within  the 
nymphaj,  the  urethral  orifice,  as  already  mentioned,  becomes  distinct  from  that 
of  the  vagina. 

In  the  male,  on  the  contrary,  the  penis  continues  to  enlarge,  and  the  margins  of 
the  groove  along  its  under  surface  gradually  unite  from  the  primitive  urethral 
orifice  behind,  as  far  forward  as  the  glans,  so  as  to  complete  the  long  canal  of  the 
male  urethra.  This  is  accomplished  about  the  fifteenth  week.  When  this  union 
remains  incomplete,  the  condition  named  hypospadias  is  produced.  In  the 
mean  time  the  prepuce  is  formed,  and,  moreover,  the  lateral  cutaneous  folds  also 
unite  from  behind  forwards,  along  the  middle  line  or  raph^,  and  thus  complete 
the  scrotum,  into  which  the  testicles  do  not  descend  until  the  last  month  of  loetal 
e.xistence. 

MAMMARY  GLANDS. 

The  mammary  glands  (mammfe),  the  organs  of  lactation  in  the 
female,  are  accessory  parts  to  the  reproductive  system.  They  give  a 
name  to  a large  class  of  animals  (Mammalia),  which  are  distinguished 
by  their  presence.  When  fully  developed  in  the  human  female,  they 
form,  together  with  the  integuments  and  a considerable  quantity  of 
fat,  two  rounded  eminences  (the  breasts)  placed  one  at  each  side  on 
the  front  of  the  thorax.  These  extend  from  the  third  to  the  sixth  or 
seventh  rib,  and  from  the  side  of  the  sternum  to  the  axilla.  A little 
below  the  centre  of  each  breast,  on  a level  with  the  fourth  rib,  projects 
a small  conical  body  named  the  nipple  (mamilla),  which  points  some- 
what outwards  and  upwards.  The  surface  of  the  nipple  is  dark,  and 
around  it  there  is  a coloured  circle  or  areola,  within  which  the  skin  is 
also  of  a darker  tinge  than  elsewhere.  In  the  virgin  these  parts  are 
of  a rosy  pink  colour,  but  they  are  always  darker  in  women  w'ho  have 
borne  children.  Even  in  the  second  month  of  pregnancy  the  areola 
begins  to  enlarge  and  acquire  a darker  tinge  ; these  changes  go  on 
increasing  as  gestation  advances,  and  are  considered  useful  and 
important  signs  in  judging  of  suspected  pregnancy.  After  lactation  is 
over,  the  dark  colour  subsides,  but  not  entirely.  The  skin  of  the 
nipple  is  marked  wdth  many  wrinkles,  and  is  covered  with  papillas; 
besides  this,  it  is  perforated  at  the  tip  with  several  foramina,  which 
are  the  openings  of  the  lactiferous  ducts  ; and  near  its  base,  as  well  as 
upon  the  surface  of  the  areola,  there  are  scattered  rounded  elevations, 
which  are  caused  by  the  presence  of  little  glands  with  branched  ducts, 
four  or  five  of  which  open  on  each  tubercle.  The  tissue  of  the  nipple 
contains  a large  number  of  vessels,  and  its  papillae  are  highly  sensitive; 
it  is  capable  of  a certain  degree  of  erection  from  mechanical  excite- 
ment, and  this  is  generally  ascribed  to  turgescence  of  its  vessels, 
which  some  regard  as  forming  a species  of  erectile  tissue. 

The  base  of  the  mammary  gland,  which  is  nearly  circular,  is 
flattened,  or  slightly  concave,  and  has  its  longest  diameter  directed 
upwards  and  outwards  towards  the  axilla.  It  rests  on  the  pectoral 


MAMMARY  GLANDS. 


575 


muscle,  and  is  connected  to  it  by  a layer  of  cellular  tissue.  The 
thickest  part  of  the  gland  is  near  the  centre,  Opposite  the  nipple,  but 
the  full  and  even  form  of  the  breasts  depends  chiefly  on  the  presence 
of  a large  quantity  of  fat,  which  lies  beneath  the  skin,  covers  the  sub- 
stance of  the  gland,  and  penetrates  the  intervals  between  its  lobes  and 
lobules.  This  fatty  tissue,  which  is  of  a bright  yellow  tinge  and  rather 
firm,  is  divided  into  lobulated  masses  by  numerous  laminae  of  fibrous 
or  very  dense  cellular  tissue,  which  are  connected  with  the  skin  on 
the  one  hand,  and  on  the  other  with  the  firm  cellular  investment  of 
the  gland  itself,  and  that  is  connected  behind  by  similar  laminae  with 
the  cellular  membrane  covering  the  pectoral  muscle:  these  laminae 
serve  to  support  the  gland.  Beneath  the  areola  and  the  nipple  there 
is  no  fat,  but  merely  the  firm  cellular  tissue  and  vessels  surrounding 
the  lactiferous  ducts. 

Structure. — The  mammary  gland  consists  of  a number  of  distinct 
glandular  masses  or  lobes,  each  having  a separate  excretory  duct, 
held  together  by  a very  firm  intervening  fibrous  or  cellular  tissue,  and 
having  some  adipose  tissue  penetrating  between  them.  Each  of  these 
divisions  of  the  gland  is  again  subdivided  into  smaller  lobes,  and  these 
again  into  smaller  and  smaller  lobules,  which  are  flattened  or  de- 
pressed, and  held  together  by  cellular  tissue,,  blood-vessels,  and  ducts. 
The  substance  of  the  lobules,  especially  as  contrasted  with  the  adja- 
cent fat,  is  of  a pale  reddish  cream-colour,  and  is  rather  firm.  It  is 
composed  principally  of  the  vesicular  commencements  of  the  lactife- 
rous ducts,  w'hich  appear  like  clusters  of  minute  rounded  cells,  having 
a diameter  from  ten  to  thirty  times  as  great  as  that  of  the  capillary 
vessels  by  which  they  are  surrounded.  These  cells  open  into  the 
smallest  branched  ducts,  which,  uniting  together  to  form  larger  and 
larger  ones,  finally  end  in  the  single  excretory  canal  corresponding  to 
one  of  the  chief  subdivisions  of  the  gland.  The  canals  proceeding 
thus  from  the  principal  lobes  composing  the  gland,  are  named  the 
galactophorous  ducts,  and  are  fifteen  to  twenty  in  number ; they  con- 
verge towards  the  areola,  beneath  which  they  become  considerably 
dilated,  especially  during  lactation,  so  as  to  form  sacs  or  sinuses  two 
or  even  three  lines  wide,  which  serve  as  temporary  though  small  re- 
servoirs for  the  milk.  At  the  base  of  the  nipple  all  these  ducts,  again 
reduced  in  size,  are  assembled  together,  those  in  the  centre  being  the 
largest,  and  then  proceed  side  by  side,  surrounded  by  cellular  tissue 
and  vessels,  and  without  communicating  with  each  other,  to  the  sum- 
mit of  the  mamilla,  where  they  open  by  separate  orifices,  which  are 
sealed  in  little  depressions,  and  are  smaller  than  the  ducts  to  which 
they  respectively  belong.  According  to  Pappenheim,  the  walls  of  the 
ducts  are  composed  of  cellular  tissue,  and  of  longitudinal  and  trans- 
verse elastic  filaments.  The  mucous  membrane  is  continuous  with 
the  common  integument  at  the  orifices  of  the  ducts;  its  epithelium  is 
scaly  or  tessellated,  and  in  the  smallest  ducts  and  their  ultimate  vesicles 
consists  of  cells  having  a diameter  very  little  exceeding  that  of  their 
nucleus. 

Blood-vessels  and  nerves. — The  arfm'es  which  supply  the  mammary 
glands  are  the  long  thoracic  and  some  other  branches  of  the  axillary 


576 


MAMMARY  GLANDS. 


artery,  the  internal  mammary,  and  the  subjacent  intercostals.  The 
vems  have  the  same  denomination.  Haller  described  a sort  of  anas- 
tomotic venous  circle  around  the  base  of  the  nipple  as  the  circuhis 
venosus.  The  nerves  are  the  anterior  and  middle  intercostal  cutaneous 
branches:  Muller  could  not  detect  any  sympathetic  nerves  accompa- 
nying the  arteries;  but  it  is  probable  that  they  exist. 

In  the  male,  the  mammary  gland  and  all  its  parts  exist,  but  quite  in 
a rudimentary  state,  the  gland  itself  measuring  only  about  six  or  seven 
lines  across,  and  two  lines  thick,  instead  of  four  inches  and  a half  wide 
and  one  and  a half  thick,  as  in  the  female.  Occasionally  the  male 
mamma,  especially  in  young  subjects,  enlarges  and  pours  out  a thin 
watery  fluid ; and,  in  some  rare  cases,  milk  has  been  secreted. 

Varieties. — Two  or  even  three  nipples  have  been  found  on  one  gland.  An  ad- 
ditional mamma  is  sometimes  met  with,  and  even  four  or  five  have  been  ob- 
served to  co-exist;  the  superadded  glands  being  most  frequently  near  the  ordinary 
ones,  but  sometimes  at  a distant  part  of  the  body,  as  the  axilla,  thigh,  or  back. 


SURGICAL  ANATOMY. 


The  surgical  anatomy  of  a large  portion  of  the  body  has  been 
already  discussed  in  connexion  with  the  principal  arteries  (voi.  i.  p, 
538,  el  seq.),  but  it  remains  to  review  certain  parts  ot  the  walls  of  the 
abdomen  and  pelvis,  with  reference  to  surgical  operations  in  which  the 
viscera  of  those  cavities  are  from  time  to  time  concerned. 

SURGICAL  ANATOMY  OF  THE  PARTS  CONCERNED  IN 
CERTAIN  ABDOMINAL  HERNIA. 

The  walls  of  the  abdomen,  when  in  a healthy  state,  unaffected  by 
injury,  disease  or  malformation,  retain  under  all  circumstances  the 
viscera  within  the  cavity,  except  where  certain  natural  openings  exist 
for  the  passage  of  blood-vessels ; but,  at  such  openings,  protrusions  of 
the  viscera,  constituting  the  disease  named  “ hernia”  or  “ rupture,” 
are  liable  to  occur  under  the  influence  of  the  compression  to  which 
the  organs  are  subjected  during  the  production  of  efforts.  For  the 
replacement  of  the  viscus  so  protruded,  an  accurate  acquaintance  with 
the  structure  of  the  part  through  which  the  protrusion  takes  place  is 
required  by  the  surgeon;  and,  on  this  account,  a separate  examination 
of  the  seat  of  each  accident  as  a surgical  region  becomes  necessary. 

Two  of  the  openings  by  which  herniae  escape  from  the  abdomen  are 
situated  close  together  at  the  groin.  One  is  the  canal  in  the  lower 
part  of  the  broad  abdominal  muscles,  which,  in  the  male,  gives  passage 
to  the  duct  and  vessels  of  the  testis  (spermatic  cord),  and  in  the  female 
to  the  round  ligament  of  the  womb.  The  second  opening  exists  at  the 
inner  side  of  the  large  femoral  blood-vessels. 

Hernial  protrusions  are  likewise  found  to  escape  at  the  umbilicus, 
in  the  course  of  the  blood-vessels  which  occupy  that  opening  in  the 
foetus  or  in  the  immediate  neighbourhood  of  the  opening,  and  at  the 
thyroid  foramen  where  the  obturator  vessels  and  nerve  pass  down- 
wards to  the  adductor  muscles  of  the  thigh.  According  to  the  situa- 
tion they  occupy  these  herniae  are  named  respectively  inguinal,  femoral, 
umbilical,  and  obturator.  They  will  now  be  separately  noticed  ; but, 
inasmuch  as  the  structure  of  the  parts  connected  with  the  umbilical 
and  obturator  herniae  is  by  no  means  intricate,  and  as,  moreover,  it  is 
noticed  with  sufficient  detail  in  text-books  of  practical  surgery,  it  will 
be  unnecessary  to  refer  further  to  those  forms  of  hernia  in  this  work. 

Before  details  are  entered  upon,  it  should  be  understood  that  as  the 
various  structures  which  are  about  to  be  reviewed  in  connexion,  have 
been  described  in  former  parts  of  this  treatise,  with  the  systems  to 
which  they  severally  belong,  we  shall  here  for  the  most  part  only  refer 
back  to  details  already  given,  occasionally  however  recalling  the 
most  important  facts,  and  adding  such  points  as  may  be  material  to 

VOL.  II.  49 


578 


INGUINAL  HERNIA. 


the  object  with  which  the  same  structures  are  now  brought  under  con- 
sideration. 

OF  THE  PARTS  CONCERNED  IN  INGUINAL  HERNIA. 

The  inguinal  liernia,  it  has  been  stated  above,  follows  the  course  of 
the  spermatic  cord  from  the  cavity  of  the  abdomen.  We  shall  there- 
fore, before  adverting  to  the  hernial  protrusions,  examine  the  structure 
of  the  abdominal  walls  in  the  neighbourhood  of  the  canal  in  which  the 
cord  is  placed;  and  tor  this  purpose  it  will  be  supposed  that  the  con- 
stituents of  those  walls  are  successively  laid  bare  and  everted  to  such 
extent  as  would  be  permitted  by  two  incisions  made  through  them,  and 
reaching,  one  along  the  linea  alba  for  the  length  of  three  or  four  inches 
from  the  pubes,  the  other  directed  from  the  upper  end  of  the  vertical 
incision  outwards  to.  the  superior  spine  of  the  ilium. 

T\\q  superficial  fascia — for  the  detailed  description  of  which  see  vol. 
i.  p.  — is  connected  along  the  fold  of  the  groin  with  Poupart’s  liga- 

ment and  the  upper  end  of  the  fascia  lata  ; and,  after  descending  over  the 
spermatic  cord  into  the  scrotum,  it  becomes  continuous  with  the  mem- 
brane of  the  same  kind  which  covers  the  perineum.  Its  thickness 
varies  much  in  difl'erent  persons,  on  account  of  the  different  quantity 
of  fat  contained  within  its  meshes;  but  in  the  scrotum  the  fascia  is 
devoid  of  fat;  as  it  also  is  elsewhere  towards  the  internal  surface, 
where  its  density  is  at  the  same  time  augmented.  From  the  various 
thickness  of  this  structure  on  the  abdomen  and  the  scrotum,  as  well 
as  in  different  persons,  it  will  be  inferred  that  the  depth  of  incision  re- 
quired to  divide  it  in  an  operation  must  vary  considerably. 

The  superfcial  vessels  of  the  groin  are  encased  by  the  fascia,  and 
are  held  to  separate  it  into  two  layers.  The  vessels  which  ramify 
over  the  inguinal  canal  and  the  scrotum  are  the  external  pudic  and 
epigastric  arteries  and  veins  (p.  619,  vol.  ii.  p.  27).  The  veins,  espe- 
cially the  epigastric,  are  considerably  larger  than  the  arteries  they 
accompany.  Some  of  these  vessels  are  wounded  in  operations  per- 
formed for  the  relief  of  strangulated  hernia;  but  the  bleeding  from 
them  is  small  in  quantity  and  rarely  requires  the  application  of  a liga- 
ture or  other  means  to  arrest  it.  The  lymphatic  glands  of  the  groin 
(see  p.  50)  admit  of  being  arranged  into  two  sets,  one  being  placed 
over  Poupart’s  ligament  and  parallel  with  that  structure  ; while  the 
other  series  is  upon  the  upper  part  of  the  thigh  at  its  middle,  about  the 
saphenous  opening  in  the  fascia  lata. 

When  the  superficial  fascia  is  removed  the  aponeurosis  of  the  exter- 
nal oblique  muscle  (see  p.  414)  is  in  view,  together  with,  in  the  male 
body,  the  spermatic  cord  (in  the  female  body,  the  round  ligament  of 
the  uterus),  which  emerges  from  an  opening  close  to  the  outer  side  of 
the  spine  of  the  pubes  (fig.  497).  The  lowest  fibres  of  the  aponeurosis 
as  they  approach  the  pubes  become  separated  into  two  bundles,  which 
leave  an  interval  between  them  for  the  passage  of  the  cord  or  ligament 
just  named.  One  of  the  bands,  the  upper  one  and  the  smaller  of  the 
two,  is  fixed  to  the  symphysis  of  the  pubes  ; and  the  lower  band,  which 
forms  the  lower  margin  of  the  aponeurosis,  being  stretched  between 
the  anterior  superior  spine  of  the  ilium  and  the  pubes  is  named 


INGUINAL  HERNIA. 


579 


Poupart’s  ligament,  or  the  femoral  arch.  This  latter  tendinous  band 
has  considerable  breadth.  It  is  fixed  at  the  inner  end  to  the  spine  of 
the  pubes,  and,  for  some  space  outside  that  process  of  the  bone,  to  the 
pectineal  ridge.  In  consequence  of  the  position  of  the  pectineal  ridge 
at  the  back  part  of  the  bone,  the  ligament  is  lucked  backwards  and  its 
upper  surface  affords  space  for  the  attachment  of  the  other  broad 
muscles,  at  the  same  time  that  it  supports  the  spermatic  cord. 
Poupart’s  ligament  does  not  lie  in  a straiglit  line  between  its  two  fixed 
points;  it  curves  downwards,  and  with  the  curved  border  the  fascia 
lata  is  connected.  It  is 


owing  to 
the  last-mentioned  fact  that  the  so- 
named  ligament,  together  with  the 
rest  of  the  aponeurosis  of  the  ex- 
ternal oblique,  is  influenced  by  the 
position  of  the  thigh,  being  relaxed 
when  the  limb  is  bent  and  the  con- 
verse. Moreover,  the  change  of 
the  position  of  the  limb  exercises  a 
corresponding  influence  on  the 
state  of  the  other  structures  con- 
nected with  Poupart’s  ligament. 

The  interval  left  by  the  separa- 
tion of  the  fibres  of  the  aponeu- 
rosis above  referred  to,  is  named 
the  external  abdominal  ring,  and 
the  two  bands  by  which  it  is 
bounded,  are  known  as  its  pillars 
or  columns.  The  space  is  trian- 
gular in  shape,  its  base  being  the 
crista  of  the  pubes,  while  the  apex 
is  at  the  point  of  separation  of  the 
twm  columns.  The  size  of  the 


Fig.  497. 


The 


ring  varies  considerably  in  different  , 

^ ■'  pillar  of  the 


aponeurosis  of  the  external  oblique 
and  the  fascia  lata. — 1.  The  iniernat 
, . • • I -11  i”">“  the  abdominal  ring.  2.  The  exieniat 

bodies  ; — in  one  case  its  sides  will  pHlar  of  same  (Ponpan's  ligameno.  3 Trans- 
be  found  closelv  applied  to  the  X®''^®  ‘he  aponeurosis.  4.  Pubic  part  of 

. 1 * I *1  • 1 lascia  lata.  5.  J he  spermatic  cord.  6.  The 

spermatic  cord;  while,  in  another,  long  saphenous  vein.  7.  Fascia  lata. 

on  the  contrary,  the  space  is  so 

considerable  as  to  be  an  obvious  source  of  weakness  to  the  abdominal 
parietes.  It  is  usually  smaller  in  the  female  than  in  the  male  body. 

Between  the  pillars  of  the  abdominal  ring  is  stretched  a thin  fascia, 
named,  from  that  circumstance,  “ intercolumnar and  a thin  diapha- 
nous membrane  prolonged  from  the  edges  of  the  opening  affords  a 
covering  (fascia  spermatica)  to  the  spermatic  cord  and  the  tunica 
vaginalis  testis.  The  cord  passes  through  the  ring  over  its  outer 
pillar. 

Internal  oblique  muscle  (vol.  i.  p.  416). — x\fter  removing  the  aponeu- 
rosis of  the  external  oblique,  this  muscle  is  laid  bare  (fig.  49S).  The 
lower  fibres  are  thin  and  often  of  a pale  colour.  Immediatelv  above 
Poupart’s  ligament  the  outer  part  is  muscular,  the  inner  part  tendinous. 
The  spermatic  cord,  when  about  to  escape  at  the  external  abdominal 


5S0 


ABDOMINAL  MUSCLES. 


ring,  passes  beneath  the  fleshy  part  of  the  muscle.  The  fibres  in  this 
situation  varying  considerably  in  direction  from  those  of  the  rest  of 
tlie  muscle,  pass  inwards  from  Poupart’s  ligament  at  first  nearly 
parallel  with  that  structure;  and,  becoming  tendinous,  they  join  with 
the  tendon  of  the  transversalis. 


Fig-.  498. 


The  aponeurosis  of  the  external  oblique  muscle  having  been  divided  and  turned  down,  the 
internal  oblique  is  brought  into  view  with  the  spermatic  cord  escaping  beneath  its  lower  edge. 
— 1.  Aponeurosis  of  the  external  oblique.  1'.  Lower  part  of  same  turned  down.  2.  Internal 
oblique  muscle.  3.  Spermatic  cord.  4.  Saphenous  vein. 

Transversalis  muscle. — This  muscle  (see  p.  417)  does  not,  in  general, 
extend  down  as  far  as  the  internal  oblique  (fig.  499);  so  that  the  latter 
being  removed,  an  interval  is  observable  betw-een  the  edge  of  the 
transversalis  and  Poupart’s  ligament,  in  which  the  transversalis  fascia 
comes  into  view;  and  in  which  the  spermatic  cord  is  seen  after  having 
penetrated  that  fascia.  The  lower  edge  of  the  muscle  is  commonly 
close  above  the  opening  for  the  cord  in  the  subjacent  membrane,  while 
the  tendon  curves  to  its  inner  side.  So  that  the  margin  of  the  muscle 
with  its  tendon  has  a semicircular  direction  with  respect  to  the 
aperture. 

The  tendinous  fibres  in  which  the  fleshy  part  of  the  two  preceding 
muscles  end,  are  connected  together  so  as  to  form  one  layer,  which 
is  named  the  “ conjoined  tendon  of  the  internal  oblique  and  transverse 
muscle.”  This  tendon  is  fixed  to  the  crest  of  the  pubes  in  front  of  the 
rectus  muscle,  and  likewise  to  the  pectineal  ridge.  It  is  thus  behind 
the  external  abdominal  ring,  and  serves  to  strengthen  the  wall  of  the 
abdomen  where  it  is  weakened  by  the  presence  of  that  opening. 

A band  of  tendinous  fibres  (fig.  499)  directed  upwards  and  inwards 
over  the  conjoined  tendon  in  a triangular  form  gives  additional  strength 


INGUINAL  HERNIA. 


After  the  removal  of  the  lower  part  of  the  external  oblique  (with  the  exception  of  a small  slip 
including  Poupart’s  ligament),  the  lower  portion  of  the  internal  oblique  was  raised,  and  thereby 
the  transversalis  muscle  and  fascia  have  been  brought  into  view.  The  femoral  artery  and  vein 
are  seen  to  a small  extent,  the  fascia  lata  having  been  turned  aside  and  the  sheath  of  the  blood- 
vessels laid  open. — 1.  External  oblique  muscle.  2.  Internal  oblique.  2'.  Part  of  same  turned 
lip.  3.  Transversalis  muscle.  Upon  the  last-named  muscle  is  seen  a branch  of  the  circumflex 
iliac  artery,  with  its  companion  veins;  and  some  ascending  tendinous  fibres  are  seen  over  the 
conjoined  tendon  of  the  two  last-named  muscles.  4.  Transversalis  fascia,  o.  Spermatic  cord 
covered  with  the  infundibuliforra  fascia  from  preceding.  6.  Upper  angle  of  the  iliac  part  of 
fascia  lata.  7.  The  sheath  of  the  femoral  vessels.  8.  Femoral  artery.  9.  Femoral  vein.  10. 
Saphenous  vein.  11.  A vein  joining  it. 

Where  the  spermatic  cord  is  in  apposition  M'ith  the  preceding 
muscle,  the  cremaster  muscle  of  the  testis  descends  over  it.  The 
fibres  which  compose  this  muscle  are,  from  their  colour,  more  easily- 
distinguished  than  the  other  investments  of  the  cord  ; and  this  is  espe- 
cially the  case  in  robust  persons  or  when  they  are  hypertrophied,  as 
sometimes  happens  in  cases  of  long-standing  hernia.  The  outer  part 
of  the  cremaster  is  much  larger  than  the  portion  connected  with  the 
pubes;  indeed,  it  sometimes  happens  that  the  latter  is  not  to  be  discerned 
even  with  most  careful  dissection  (see  vol.  ii.  p.  542). 

When  observed  in  diiferent  bodies  the  lower  part  of  the  internal  oblique  and 
transverse  muscles  will  be  found  to  present  some  differences  in  their  physical 
characters  as  well  as  in  the  manner  in  which  they  are  disposed  with  respect  to 
the  spermatic  cord.  Thus  : — 

a.  The  transversalis,  in  some  cases,  is  attached  to  but  a small  part  of  Poupart’s 
ligament,  and  leaves,  therefore,  a larger  part  of  the  abdominal  wall  without  its 
support.  On  the  other  hand,  that  muscle  may  be  found  to  extend  so  loxv  down 
as  to  cover  the  internal  abdominal  ring  together  with  the  spermatic  cord,  for  a 

49* 


581 


to  the  abdominal  wall  in  the  same  situation,  but  the  fibres  of  this 
structure  are  often  very  indistinct. 


Fig.  499. 


582 


INGUINAL  HERNIA. 


short  space.  Not  unfrequently  the  lleshy  fibres  of  the  two  muscles  are  blended 
togetlier  as  well  as  their  tendons. 

b.  Cases  occasionally  occur  in  which  the  spermatic  cord,  instead  of  escaping 
beneath  the  margin  of  the  internal  oblique,  is  found  to  pass  through  the  muscle, 
so  that  some  muscular  fibres  are  below  as  well  as  above  it.  And  examples  of 
the  transversalis  being  penetrated  by  that  structure  in  the  same  manner  are 
recorded.* 

c.  In  his  latest  account  of  the  structure  of  these  parts  Sir  A.  Cooper  described 
the  lower  edge  of  the  transversalis  as  curved  all  round  the  internal  ring  and  the 
spermatic  cord.  “ But  the  lower  edge  of  the  transversalis  has  a very  peculiar 
insertion,  which  I have  hinted  at  in  my  work  on  hernia.  It  begins  to  be  fixed  in 
Poupart’s  ligament,  almost  immediately  below  the  commencement  of  the  internal 
ring,  and  it  continues  to  be  inserted  behind  the  spermatic  cord  into  Poupart’s 
ligament  as  far  as  the  attachment  of  the  rectus.”!  With  this  disposition  of  its 
fibres,  the  muscle  would,  in  the  opinion  of  the  last-cited  authority,  have  the 
effect  of  a sphincter,  in  closing  the  internal  ring,  and  would  thus  tend  to  prevent 
the  occurrence  of  hernia.  But  the  principal  object  with  which  the  attention  of 
surgeons  has  been  fi.xed  on  the  muscles  in  this  situation,  is  in  order  to  account 
for  the  active  strangulation  of  hernial  protrusions  at  the  internal  abdominal  ring, 
and  in  the  inguinal  canal. 

Fascia  transversalis. — This  membrane  is  described  as  part  of  the 
general  lining  of  the  abdominal  walls  at  p.  302,  vol.  i.  Closely  con- 
nected with  the  transversalis  muscle  by  means  of  the  cellular  membrane 
interposed  between  the  fleshy  fibres  of  the  muscle,  it  is  united  below 
to  the  posterior  edge  of  Poupart’s  ligament,  there  joining  with  the 
fascia  iliaca ; and  on  the  inner  side  it  blends  with  the  conjoined  tendon 
of  the  internal  oblique  and  transversalis  muscles,  as  well  as  with  the 
tendon  of  the  rectus.  The  fascia  possesses  very  different  degrees  of 
density  in  different  cases;  in  some  being  little  more  than  a loose 
cellular  texture,  while  in  others  it  is  so  resistant  at  the  groin, — towards 
which  part  it  increases  in  thickness,  and  especially  at  the  inner  side 
of  the  internal  abdominal  ring — that  it  is  calculated  to  afford  material 
assistance  to  the  muscles  in  supporting  the  viscera.  By  an  oval 
opening  in  this  membrane  the  spermatic  cord  (or  the  round  ligament 
of  the  womb)  begins  its  course  through  the  abdominal  parietes.  This 
opening,  named  the  internal  abdominal  ring,  is  opposite  the  middle  of 
Poupart’s  ligament  and  usually  close  above  that  structure,  but  occa- 
sionally at  a distance  of  three  or  four  lines  from  it.  Its  size  varies  a 
good  deal  in  diflerenl  persons,  and  is  considerably  greater  in  the  male 
than  the  female.  From  the  edge  of  the  ring  a thin  funnel-shaped 
elongation  (infundibuliform  fascia  ; fascia  spermatica  interna.  Cooper), 
is  continued  over  the  vessels  of  the  spermatic  cord. 

Epigastric  artery. — The  position  of  this  vessel  is  one  of  the  most 
important  points  in  the  anatomy  of  the  inguinal  region,  from  the  close 
connexion  which  it  has  with  the  different  forms  of  inguinal  hernia 
and  with  the  femoral  hernia.  Accompanied  by  two  veins  (in  some 
instances  by  only  one)  the  vessel  ascends  under  cover  of  the  fascia 
last  described  obliquely  to  the  rectus  muscle,  behind  which  it  then 
proceeds  to  its  ultimate  distribution  (see  p.  619).  In  this  course  the 

♦ Rechcrclies  Anatomiques  sur  les  Hernies,  &.C.,  par  .T.  Cloquet,  pp.  18  and  23,  Paris, 
1817.  Inguinal  and  Femoral  Herniae,  by  G.  J.  Guthrie,  plate  1,  London,  1833. 

t Observations  on  the  Structure  and  Diseases  of  the  Testis,  second  edition,  p.  36.  Ed. 
by  Bransby  B.  Cooper,  F.R.S.  London,  1841. 


inguinal  canal. 


583 


artery  runs  along  the  inner  side  of  the  internal  abdominal  ring — close 
to  the  edge  of  the  aperture  (fig.  501),  or  at  a short  interval  from  it. 
The  vessels  of  the  spermatic  cord  are  therefore  near  to  the  epigastric 
artery;  and  the  vas  deferens,  in  turning  from  the  ring  into  the  pelvis, 
may  be  said  to  hook  round  it. 

The  Inguinal  Canal. — This,  the  channel  by  which  the  spermatic 
cord  passes  through  the  abdominal  muscles  to  the  testis,  begins  at  the 
internal  abdominal  ring,  and  ends  at  the  external  one.  It  is  oblique  in 
its  direction,  being  parallel  with  and  immediately  above  the  inner  half 
of  Poupart’s  ligament;  and  it  measures  two  inches  in  length.  In  front, 
the  canal  is  bounded  by  the  aponeurosis  of  the  external  oblique  muscle 
in  its  whole  length,  and  at  the  outer  end  by  the  fleshy  part  of  the 
internal  oblique  also ; behind  it  is  the  fascia  transversalis,  together 
with,  towards  the  inner  end,  the  conjoined  tendon  of  the  two  deeper 
abdominal  muscles.  Below,  the  canal  is  supported  by  the  broad 
surface  of  Poupart’s  ligament,  which  separates  it  from  the  sheath  of 
the  large  blood-vessels  descending  to  the  thigh,  and  from  the  femoral 
canal  at  the  inner  side  of  those  vessels. 

The  spermatic  cord,  which  occupies  the  inguinal  canal,  is  composed 
of  the  arteries,  veins,  lymphatics,  nerves,  and  excretory  duct  (vas 
deferens)  of  the  testis,  together  with  a quantity  of  loose  cellular 
membrane  mixed  up  with  those  parts.  The  direction  of  the  vessels 
just  enumerated  requires  notice.  The  artery  and  vein  incline  outwards 
from  the  lumbar  part  of  the  vertebral  column  to  reach  the  internal 
abdominal  ring,  where,  after  being  joined  by  the  vas  deferens  as  it 
emerges  from  the  pelvis,  they  change  their  course,  inclining  inwards 
along  the  inguinal  canal ; at  the  end  of  which  they  become  vertical. 
There  are  thus  repeated  alterations  in  the  direction  of  the  vessels; 
and  while  at  the  beginning  and  ending  all  are  close  to  the  middle  line 
of  the  body,  they  are  considerably  removed  from  that  point  where 
they  come  together  to  emerge  from  the  abdominal  cavity. 

The  coverings  given  from  the  constituent  parts  of  the  abdominal 
wall  to  the  spermatic  cord  and  the  testis,  namely,  the  cremasteric 
muscular  flbres,  with  the  tw'o  layers  of  fascia  between  which  those 
fibres  are  placed  (the  infundibuliform  and  spermatic  fascias),  are  very 
thin  in  their  natural  state;  but  they  may  be  readily  distinguished  in  a 
surgical  operation  from  the  investing  superficial  fascia,  by  their  com- 
parative density  and  the  absence  of  fat. 

In  order  to  examine  the  peritoneum  at  the  groin  it  wdll  be  best  to 
divide  that  membrane  with  the  abdominal  muscles  by  two  incisions 
drawn  from  the  umbilicus — one  to  the  ilium,  the  other  to  the  pubes. 
The  flap  thus  formed  being  held  somewhat  outwards,  and  kept  tense, 
a favourable  view  will  be  obtained  of  the  two  fossae  {inguinal  fosses  or 
pouches)  with  the  intervening  crescentic  fold.  This  fold  is  formed  bv 
the  cord  remaining  from  the  obliterated  umbilical  artery,  which  being 
shorter  than  the  outer  surface  of  the  serous  sac,  projects  it  inwards ; 
and  as  the  length  of  the  cord  difiers  in  different  cases,  so  likewise  does 
the  size  and  prominence  of  the  peritoneal  fold  vary  accordingly. 

The  lowest  part  of  the  outer  fossa  will  be  generally  found  opposite 
to  the  entrance  into  the  internal  abdominal  ring  and  the  femoral  ring, 


584 


INGUINAL  HERNIA2. 


while  the  inner  one  corresponds  with  the  situation  of  the  external 
abdominal  ring.  But  the  cord  representing  the  umbilical  artery, 
which,  it  has  been  stated,  causes  the  projection  of  the  serous  mem- 
brane into  a fold,  does  not  uniformly  occupy  the  same  position  in  all 
cases.  Most  frequently  it  is  separated  by  an  interval  from  the 
epigastric  artery  (fig.  501),  while  in  some  cases  it  is  immediately 
behind  that  vessel.  There  is  necessarily  a corresponding  variation  in 
the  extent  of  the  external  peritoneal  fossa.  This  fact  will  find  its 
practical  application  when  the  internal  form  of  inguinal  hernia  is 
under  consideration. 

Between  the  peritoneum  and  the  fascia  lining  the  abdominal  muscles 
is  a connecting  layer  of  cellular  structure,  named  the  subserous  cellular 
membrane.  A considerable  quantity  of  fat  is  in  some  cases  found  in 
this  membrane. 

The  relative  position  of  some  of  the  parts  above  referred  to  may  be 
here  conveniently  stated,  by  means  of  measurements,  made  by  Sir  A. 
Cooper,  and  adopted  after  examination  by  J.  Cloquet.  But  as  the 
distance  between  given  parts  varies  in  different  cases,  the  following 
measurements  must  only  be  regarded  as  a general  average : — 


From  the  symphysis  of  the  pubes  to  the  anter.  supr. 

spine  of  the  ilium 

From  the  same  point  to  the  spine  of  the  pubes  . . 

“ to  the  inner  part  of  the  external 

abdominal  ring 

“ to  the  inneredge  of  the  internal 

abdominal  ring 

“ to  the  epigastric  artery  on  the 

inner  side  of  the  internal  abdominal  ring  . . 


Male. 

Female. 

5i  inches.  . . 

H “ . . 

. . If  “ 

o|  » . . 

..I  “ 

3 » . . 

CO 

2|  “ . . 

. . “ 

From  the  preceding  account  of  the  structure  of  the  abdominal  wall 
at  the  groin,  it  will  be  inferred  that  the  defence  against  the  protrusion 
of  the  viscera  from  the  cavity  is  here  weaker  than  at  other  parts. 
The  external  oblique  muscle  and  the  fascia  transversalis  are  perforated, 
while  the  two  intervening  muscles  are  thinner  than  elsewhere,  and 
more  or  less  defective.  To  this  it  must  be  added  that  the  viscera  are 
impelled  towards  the  same  part  of  the  abdomen  by  the  contraction 
of  the  diaphragm  and  the  other  abdominal  muscles,  which  occurs  in 
the  production  of  efforts  to  overcome  resistance ; and  these  are  the 
circumstances  under  which  protrusions  actually  take  place. 


INGUINAL  HERNIiE. 

The  protrusions  of  the  viscera  or  hernias,  which  occur  in  the  course 
of  the  inguinal  canal,  are  named  “ Inguinal.”  Of  this  form  of  the 
disease  two  varieties  are  recognised : and  they  are  distinguished 
according  to  the  part  of  the  canal  which  they  first  enter  into,  as  well 
as  by  the  position  they  bear  with  respect  to  the  epigastric  artery. 
Thus,  when  the  hernia  takes  the  course  of  the  inguinal  canal  from  its 
commencement,  it  is  named  oblique,  because  of  the  direction  of  the 
canal,  or  external,  from  the  position  its  neck  bears  with  respect  to  the 


OBLIQUE  INGUINAL  HERNIA. 


585 


epi?astric  artery.  On  the  other  hand,  when  the  protruded  part, 
without  following  the  length  of  the  canal,  is  forced  at  once  through  its 
termination,  i.  e.,  through  the  external  abdominal  ring,  the  hernia  is 
named  from  its  course  direct,  or,  from  its  relation  to  the  epigastric 
artery,  internal.  In  these,  the  two  principal  varieties  of  inguinal 
hernia,  there  are  some  modifications  which  will  be  adverted  to  in  the 
special  notice  of  each. 

Oblique  inguinal  hernia. — In  the  common  form  of  this  hernia  the 
protruded  viscus  carries  before  it  a covering  of  peritoneum  (the  sac  of 
the  hernia),  derived  from  the  outer  fossa  of  that  serous  membrane; 
and  in  passing  along  the  inguinal  canal  to  the  scrotum,  it  is  succes- 
sively clothed  with  the  coverings  given  to  the  spermatic  vessels  from 
the  abdominal  parietes.  The  hernia  and  its  sac  lie  directly  in  front 
of  the  vessels  of  the  spermatic  cord,  fig.  503  (the  intestines  and  the 
peritoneum  having  the  same  position  relatively  to  those  vessels  in  the 
abdomen) ; but  when  the  disease  is  of  long  standing  the  vessels  may 
be  found  to  be  separated  one  from  the  other,  and  pressed  more  or  less 
towards  the  side  or  even  the  fore  part  of  the  sac  under  the  influence 
of  the  weight  of  the  tumour.  The  hernia  does  not  extend  below'  the 
testis  even  when  it  attains  large  size.  That  it  does  not  is,  doubtless, 
ow'ing  to  the  intimate  connexion  which  the  coverings  of  the  cord  have 
with  the  tunica  vaginalis  testis. 

When  the  hernia  does  not  extend  beyond  the  inguinal  canal,  it  is 
distinguished  by  the  name  bubonocele ; and  when  it  reaches  the  scrotum, 
it  is  commonly  named  from  that  circumstance  scrotal  hernia. 

There  are  two  other  varieties  of  oblique  inguinal  hernia,  in  which 
the  peculiarity  depends  on  the  condition  of  the  process  of  peritoneum 
that  accompanies  the  testis  when  this  organ  is  moved  from  the  abdomen. 
In  ordinary  circumstances,  the  part  of  the  peritoneum  connected 
immediately  with  the  testis,  becomes  separated  from  the  general  cavity 
of  that  serous  membrane  by  the  obliteration  of  the  intervening  canal, 
fig.  500,  b;  and  the  hernial  protru- 
sion occurring  after  such  oblitera-  Fig-.  500. 

tion  has  been  completed,  carries 
with  it  a distinct  serous  investment 
— the  sac.  But  if  the  hernia  should 
be  formed  before  the  process  of 
obliteration  is  begun  (fig.  500,  a), 
the  protruded  part  is  then  received 
into  the  cavity  of  the  tunica  vagi- 
nalis testis,  which  serves  in  the 
place  of  its  sac.  In  this  case  the 
hernia  is  named  congenital  (hernia 

, • T r' \ T.  Plans  intended  to  represent  a small  part  of 

tunicm  vaginalis  (_/OOper).  It  is  peritoneum  and  the  tunica  vaginalis  testis, 
thus  designated,  because  the  con-  in  the  first,  a,  the  serous  investment  of  the 

ditinn  nppPQ^arv  fnr  itt;  formation  elongation  from  the 

QltlOn  necessary  lor  its  lormauon  peritoneum;  while  in  the  second.  B,  the  two 

usually  exists  only  about  the  time  membranes  are  shown  distinct  one  from  the 

of  bir'th;  but  the  same  variety  of  The  peritoneal  cavity.  2.  The  testis. 

the  complaint  is  occasionally  found  to  be  first  formed  in  the  adult, 
obviously  in  consequence  of  the  tunica  vaginalis  remaining  unclosed, 


58G 


DIRECT  INGUINAL  HERNIA. 


— Still  continuous  with  the  peritoneum.  The  congenital  hernia,  should 
it  reach  the  scrotum,  passes  below  the  testis;  and  this  organ  being 
imbedded  in  the  protruded  viscus,  a careful  examination  is  necessary, 
in  order  to  detect  its  position.  This  peculiarity  serves  to  distinguish 
the  congenital  from  the  ordinary  form  of  the  disease. 

To  the  second  variety  of  inguinal  hernia,  in  which  the  distinguishing 
character  depends  on  the  state  of  the  tunica  vaginalis  testis,  the  name 
“ infantile”  has  been  applied  (Hey).  The  hernia  in  this  case  is  covered 
with  a distinct  sac,  the  peculiarity  consisting  in  the  circumstance  of 
the  rupture  with  its  sac  being  invested  by  the  upper  end  of  the  tunica 
vaginalis.  The  relative  position  of  the  two  serous  membranes  (the 
hernial  sac  and  the  tunica  vaginalis)  may  be  accounted  for  by  sup- 
posing the  hernia  to  descend  when  the  process  of  peritoneum,  which 
accompanies  the  lestis  from  the  abdomen,  has  been  merely  closed  at 
the  upper  end,  but  not  obliterated  for  any  length.  As  the  tunica  vagi- 
nalis at  this  period  extends  upwards  to  the  wall  of  the  abdomen,  the 
hernia,  in  its  descent,  soon  meets  that  membrane  and  becomes  invested 
by  it.  The  exact  mode  of  the  investment  has  not  yet  been  clearly 
made  out  by  dissection.  It  may  be  that  the  hernia  passes  behind  the 
upper  end  of  the  large  serous  tunic  of  the  testis  which  then  laps  round 
the  sac  from  before,  or  that  the  tunica  vaginalis  is  inverted  from  above 
so  as  to  receive  the  hernia  in  a depression.  But  the  fact  most  material 
for  the  surgeon  is  fully  ascertained,  namely,  that  during  an  operation 
in  such  a case  the  hernial  sac  is  met  with  only  after  another  serous 
bag  (the  tunica  vaginalis  testis)  has  been  divided.  The  peculiarity 
here  described  has  been  repeatedly  found  present  in  the  recently  formed 
hernia  of  grown  persons.  The  term  infantile,  therefore,  like  congenital, 
has  reference  to  the  condition  of  certain  parts  rather  than  to  the  period 
of  life  at  which  the  disease  is  first  formed. 

In  the  female  oblique  inguinal  hernia  follow's  the  course  of  the  round 
ligament  of  the  uterus  along  the  inguinal  canal,  in  the  same  manner 
as  in  the  male  it  follows  the  spermatic  cord.  After  escaping  from  the 
external  abdominal  ring,  the  hernia  lodges  in  the  labia  pudendi.  The 
coverings  are  ,the  same  as  those  in  the  male  body,  with  the  exception 
of  the  cremaster,  which  does  not  exist  in  the  female;  but  it  occa- 
sionally happens  that  some  fibres  of  the  internal  oblique  muscle  are 
drawn  down  over  this  hernia  in  loops,  so  as  to  have  the  appearance  of 
a cremaster  (Cloquet). 

A strictly  congenital  inguinal  hernia  may  occur  in  the  female,  the 
protruded  parts  being  received  into  the  little  diverticulum  of  the  peri- 
toneum (canal  of  Nuck),  which  sometimes  extends  into  the  inguinal 
canal  with  the  round  ligament.  But  as  this  process  of  the  peritoneum, 
in  such  circumstances,  would  probably  not  differ  in  any  respect  from 
the  ordinary  sac,  there  are  no  means  of  distinguishing  a congenital 
hernia  in  the  female  body. 

Direct  inguinal  hernia  (internal  : ventro-inguinal).  Instead  of  fol- 
lowing the  whole  course  of  the  inguinal  canal,  in  the  manner  of  the 
hernia  above  described,  the  viscus  in  this  case  is  protruded  from  the 
abdomen  to  the  groin  directly  through  the  lower  end  of  the  canal,  at 


DIRECT  INGUINAL  HERNIA. 


587 


the  external  abdominal  ring  ; 
and  at  this  point  the  two  forms 
of  hernia,  if  they  coexisted, 
would  come  together.  At  the 
part  of  the  abdominal  wall 
through  which  the  direct  ingui- 
nal hernia  finds  its  way,  there 
is  recognised  on  its  posterior 
aspect  a triangular  interval,  the 
sides  of  which  are  formed  by 
the  epigastric  artery  and  the 
margin  of  the  rectus  muscle,  the 
base  by  Poupart’s  ligament  (fig. 
501).  It  is  commonly  named  the 
triangle  of  Hesselbach.  Through 
this  space  the  hernia  is  protruded, 
carrying  before  it  a sac  from  the 
internal  fossa  of  the  peritoneum  ; 
and  it  is  in  general  forced  on- 
wards directly  into  the  external 
abdominal  ring. 


Fig.  501. 


A portion  of  the  wall  of  the  abdomen  and  of 
the  pelvis  is  here  seen  on  the  posterior  aspect,  the 


The  coverings  of  this  hernia,  innominatnm  of  the  left  side  with  the  soft 
, . , P 1 . parts  connected  with  it  having  been  removed 


taking  them  in  the  order  in  from  the  rest  of  the  body. — I.  Symphysis  of 
which  they  are  successively  ap-  P“bes.  r.  Horizontal  branch  of  same  2.  Irre- 
1 j ■ .'1  gular  surface  of  the  ilium  which  has  been  sepa- 

plied  to  the  protruded  viscus,  are  rated  from  the  sacrum.  3.  Spine  of  ischium. 

the  following  : The  peritoneal  f Tuberosity  of  same.  5.  Obturator  internus. 

j . ° I ‘ , o.  Kectus,  covered  with  an  elongation  from 

sac  and  the  cellular  membrane  7.  Fascia  transversalis.  8.  Fascia  iliaca  covering 
which  adheres  to  it,  the  fascia  ■'■‘^cus  inuscle.  9.  Psoas  magnus  cut.  10.  Iliac 
. !•  .1  . J arterj'.  11.  Iliac  vein.  12.  Epigastric  artery  and  its 

trsns VGrS3.1lS)  the  tendon  cominon  two  accompanying  veins.  .13.  Vessels  of  sper- 
to  the  internal  oblique  and  trans-  cord,  entering  the  abdominal  wall  at  the 

1 /n  ] L mternal  ring.  The  ring  was  in  ihis  case  of  small 

verse  muscles  (tig*  502),  and  Ine  size.  14. Two  obturator  veins.  15.  The  obliterated 
intercolumnar  (external  sperma-  umbilical  artery.  This  cord,  U will  be  remem- 
..  V p . 1 ’ i r .1  bered,  is  not  naturally  m contact  with  the  abdo* 

tic)  fascia  derived  from  the  mai-  minal  parletes  in  this  situation. 

gin  of  the  external  abdominal 

ring,  together  with  the  superficial  fascia  and  the  integuments. 

With  respect  to  one  of  the  structures  enumerated,  namely,  the 
common  tendon  of  the  two  deeper  muscles,  considerable  variety 
exists  as  to  its  disposition  in  different  cases.  In  place  of  being 
covered  by  that  tendon,  (which  my  own  observations  lead  me  to 
regard  as  the  most  frequent  arrangement,)  the  hernia  may  be  found 
to  pass  through  an  opening  in  its  fibres,  or  to  escape  beneath  it  (fig. 
503).  Cremasteric  muscular  fibres  are  met  with  (rarely,  however) 
upon  this  hernia. 

The  spermatic  cord  is  commonly  placed  behind  the  outer  part  of 
the  direct  inguinal  hernia,  especially  at  the  external  abdominal  ring 
(figs.  502-3).  It  is  here  that  the  hernia  and  the  cord  in  most  cases 
first  come  together;  and  their  relative  position  results  from  the  points 
at  which  they  respectively  pass  through  the  ring,  the  former  being 
upon  the  crista  of  the  pubes,  while  the  latter  drops  over  the  outer 
pillar  of  the  opening.  The  hernial  sac  is  not,  however,  in  this  ca.se 


588 


DIRECT  INGUINAL  HERNIA. 


(as  the  sac  of  the  external  form  of  the  disease  is)  in  contact  with  the 
vessels  of  the  cord.  The  investments  given  from  the  fascia  transver- 
salis  to  those  vessels  and  to  the  hernia  respectively,  are  interposed. 

Fig.  502.  Fig.  503. 


Fig.  502  A direct  inguinal  hernia  on  the  left  eicle,  covered  by  the  conjoined  tendon  of  the 
internal  oblique  and  transverse  muscles. — 1.  Aponeurosis  of  the  external  oblique.  2.  Internal 
oblique  turned  up.  3.  Transversalis  muscle.  4.  Fascia  transversalis.  5.  Spermatic  cord. 
6.  The  hernia.  N.B.  A small  part  of  the  epigastric  artery  is  seen  through  an  opening  made  in 
the  transversalis  fascia. 

Fig.  503.  A small  oblique  inguinal  hernia,  and  a direct  one,  are  seen  on  the  right  side.  A 
little  of  the  epigastric  artery  has  been  laid  bare,  by  dividing  the  fascia  transversalis  immediately 
over  it. — 1.  Tetidon  of  the  external  oblique.  2.  Internal  oblique  turned  up.  3.  Transversalis. 
4.  Its  tendon  (the  epigastric  artery  is  shown  below  this  number).  5.  The  spermatic  cord  (its 
vessels  separated).  6.  A bubonocele.  7.  Direct  bernia  protruded  beneath  the  conjoined  tendon 
of  the  two  deeper  muscles,  and  covered  by  an  elongation  from  the  fascia  transversalis. 

But  the  point  at  which  the  internal  inguinal  hernia  passes  through  the 
triangular  space  above  described  as  marked  on  the  posterior  aspect  of 
the  abdominal  wall,  is  subject  to  some  variation.  Instead  of  pushing 
directly  through  the  external  abdominal  ring  (the  most  frequent  position), 
the  hernia  occasionally  enters  the  inguinal  canal  nearer  to  the  epigastric 
artery,  and  passing  through  a portion  of  the  canal  to  reach  the  ex- 
ternal ring,  has  therefore  a certain  degree  of  obliquity.  This  change 
in  position  may  coincide  with  a change  of  the  peritoneal  fossa,  which 
furnishes  the  hernial  sac — a change,  namely,  from  the  internal  fossa 
to  the  external  one.  The  alteration  of  the  fossa  does  not  however  in 
ail  cases  coincide  with  a change  in  the  position  of  the  hernia;  for  the 
cord  remaining  from  the  obliteration  of  the  umbilical  artery,  (which 
it  is  that  separates  the  fossae,)  instead  of  crossing  behind  the  triangle 
of  Hesselbach  so  as  to  leave  room  at  either  side  of  it  for  a hernia  to 
penetrate  that  space,  is,  it  has  been  already  stated,  sometimes  directly 
behind  the  epigastric  artery  : — indeed,  according  to  the  observations 
of  Cloquet,  it  is  most  frequently  in  this  position;*  and  when  the  cord 
in  question  is  so  placed,  the  hernia,  whatever  may  be  its  position  in 


* Recherchesi,  &.C.,  p.  39,  note. 


STRANGULATED  INGUINAL  HERNIA. 


589 


the  triangle  of  Hesselbach,  can  occupy  only  the  internal  peritoneal 
fossa.  The  inference,  however,  most  important  in  a practical  or  sur- 
gical point  of  view,  to  be  drawn  from  the  varying  position  of  the  neck 
of  the  internal  hernia,  has  reference  not  to  the  cord  just  alluded  to, 
but  to  the  epigastric  artery — i.  e.  to  the  greater  or  less  distance  of  the 
neck  of  the  sac  from  that  vessel. 

The  investments  of  the  internal  hernia  are  likewise  liable  to  be  in- 
fluenced by  the  position  at  which  it  penetrates  the  abdominal  wall.  It 
is  in  all  likelihood  when  the  protrusion  occurs  outside  the  ordinary 
situation,  that  the  hernia  escapes  beneath  the  conjoined  tendon  of  the 
two  deeper  muscles.  It  is,  moreover,  under  the  same  circumstances 
that  hernia  is  more  directly  in  front  of  the  spermatic  cord,  and  that 
the  cremasteric  fibres  are  among  its  investments.* 

The  internal  inguinal  hernia  is  very  rarely  met  with  in  the  female. 
In  the  single  example  of  the  disease  that  I have  had  an  opportunity  of 
observing,  as  well  as  in  the  cases  (a  very  small  number)  which  I have 
found  recorded  in  books,  the  hernia,  though  not  inconsiderable  in  size, 
was  still  covered  wdth  the  tendon  of  the  external  oblique  muscle.f 

Distinctive  diagnosis  of  oblique  and  direct  inguinal  hernice. — The 
following  circumstances,  which  are  brought  together  from  the  facts 
detailed  in  the  preceding  pages,  or  arc  inferences  from  those  facts,  will 
serve  to  distinguish  the  two  forms  of  the  disease  one  from  the  other. 
The  first-named  hernia,  when  recently  formed,  is  elongated  and  nar- 
row at  its  upper  part,  being  restrained  by  the  tendon  of  the  external 
oblique  muscle.  It  is,  however,  attended  with  a degree  of  fulness  in 
the  inguinal  canal,  as  well  as  tenderness,  upon  pressure  being  made 
over  the  canal.  After  passing  through  the  external  abdominal  ring,  it 
is  observed  to  be  directly  in  front  of  the  spermatic  cord.  The  direct 
hernia,  when  of  small  size,  is  globular ; it  is  protruded  more  imme- 
diately over  the  pubes;  causes  no  fulness  or  tenderness  in  the  canal; 
and  the  spermatic  cord  is  usually  behind  its  outer  side.  But  the  dis- 
tinction between  the  two  hernias  admits  of  being  made  only  when  the 
disease  is  recent  and  the  tumour  moderate  in  size;  for  when  oblique 
inguinal  hernia  is  of  long  standing,  and  has  attained  considerable  size, 
the  obliquity  of  the  inguinal  canal  no  longer  remains, — the  internal 
ring  being  enlarged,  and  brought  inwards  opposite  the  external  one, — 
while  at  the  same  time  the  epigastric  artery,  borne  inwards  by  the 
hernia,  curves  along  the  inner  side  of  the  sac.  Under  this  change,  the 
oblique  hernia  assumes  the  appearance  of  one  primarily  direct. 

* Mr.  Ellis  informs  me,  that  in  dissecting-  cases  of  internal  hernia,  he  has  repeatedly 
found  fibres  of  the  cremaster  spread  over  it,  when  the  tumour  was  nearer  than  usual  to  the 
epigastric  artery,  and  only  in  this  event. 

t See  “Treatise  on  Ruptures,”  by  Mr.  Lawrence,  4th  edit.  p.  213,  and  an  essay  by  M. 
Velpeau  in  “ Annales  de  Chirurgie  Fran^aise  et  etrangere,”  tom.  i.  p.  352. 

M.  Velpeau,  in  the  essay  just  referred  to,  proposes  to  recognise  three  varieties  of  internal 
hernia,  viz.,  1,  the  ordinary  form,  which  passes  .straight  through  the  external  abdominal 
ring  ; 2,  an  outer  oblique  variety,  which  passes  through  a part  of  the  inguinal  canal ; and, 
3,  an  inner  oblique  one,  which,  entering  the  abdominal  wall  close  to  the  edge  of  the  rectus 
muscle,  is  directed  outwards  in  order  to  reach  the  opening  in  the  external  oblique  muscle. 
The  first  two  forms  adverted  to  by  M.  Velpeau  have  been  described  in  the  text.  With 
respect  to  the  third  variety  or  class  sought  to  be  introduced  by  that  surgeon,  it  should  be 
observed  that  he  seems  to  have  been  led  to  propose  it  by  the  observation  of  a single  case — 
an  example  of  internal  hernia  in  the  female. 

VOL.  II.  50 


590 


STRANGULATED  INGUINAL  HERNIA. 


Operations  for  the  relief  of  inguinal  hernia. — This  account  of  the 
disposition  of  the  parts  connected  with  the  difl'erent  forms  of  inguinal 
hernia,  may  be  concluded  by  a brief  statement  of  the  application  of 
the  anatomical  facts  in  practical  surgery,  either  in  simply  replacing 
the  hernial  protrusion,  or  in  the  operation  required  to  attain  that  object 
when  the  hernia  is  otherwise  irreducible.  In  the  efforts  to  effect  the 
replacement  of  the  protruded  parts  (the  taxis),  it  is  to  be  borne  in  mind 
that  the  abdominal  muscles,  which  in  most  cases  are  the  sole  obstacle 
to  the  attainment  of  that  end,  become  relaxed,  to  some  extent,  by  flex- 
ing the  thigh  and  inclining  the  trunk  forwards.  The  direction,  too, 
which  the  protruded  part  follows  through  the  abdominal  walls,  ought 
to  influence  the  direction  given  to  the  pressure  required  in  restoring  it. 

When  the  operation  required  to  set  free  the  constriction  w’hich  pre- 
vents the  restoration  of  the  protruded  viscus  to  the  abdomen  is  under- 
taken, the  parts  covering  the  hernia  or  a portion  of  it  at  the  upper  end, 
are  to  be  divided,  so  as  to  allow  the  introduction  of  a knife  beneath 
the  “ stricture  and  this  (the  stricture)  will  be  found  at  the  external 
ring,  or,  more  frequently,  at  the  internal  one.  To  accomplish  the  ob- 
ject, the  tendon  of  the  external  oblique  is  to  be  laid  bare  by  an  incision, 
beginning  somewhat  above  the  upper  end  of  the  hernia,  and  extending 
downw'ards  below  the  external  ring.  If,  on  examination,  the  stricture 
should  be  ascertained  to  be  at  the  last-named  opening,  the  division  of 
a few  fibres  of  its  circumference  will  allow  a sulhcient  dilatation  for 
the  replacement  of  the  hernia  ; but  if,  as  generally  happens,  the  seat  of 
the  stricture  should  prove  to  be  higher  up, — in  the  inguinal  canal  or  at 
the  internal  ring,  the  aponeurosis  of  the  external  oblique  is  to  be  cut 
through  over  the  canal,  and  the  lower  edge  of  the  internal  muscles, 
one  of  which  commonly  constitutes  the  stricture,  is  then  to  be  divided 
on  a director  insinuated  beneath  them. 

In  the  operation  indicated  in  the  last  paragraph,  the  sac  of  the  hernia 
is  supposed  to  be  left  unopened, — the  course  which  it  is  best  to  adopt 
when  the  stricture  is  external  to  that  membrane.  Occasionally,  how- 
ever, it  happens  that  the  sac  itself  is  the  cause  of  the  constriction. 
When  this  is  the  case,  or  when  from  some  other  reason  the  surgeon  is 
unable,  after  such  an  operation  as  that  above  noticed,  to  replace  the 
hernia,  it  becomes  necessary  to  lay  the  sac  open,  in  order  to  divide  the 
constriction  at  its  neck.  When  the  incision  required  in  the  last-men- 
tioned step  of  the  operation  is  being  made,  the  epigastric  artery  is  not 
to  be  overlooked.  From  the  position  that  vessel  holds,  with  respect 
to  the  oblique  and  direct  forms  of  hernia  respectively,  it  necessarily 
follows  that  an  incision  outwards  through  the  neck  of  the  sac,  in  the 
former  variety  of  the  disease,  and  inwards  in  the  latter,  would  be  free 
from  risk  on  account  of  the  artery  (fig.  503) ; but,  inasmuch  as  the 
oblique  hernia  is  liable,  in  time,  to  assume  the  appearance  of  one  pri- 
marily direct  (see  last  page),  and  a want  of  certainty  as  to  the  diag- 
nosis must,  on  this  account,  exist  in  certain  cases, — as,  moreover,  it  is 
advantageous  to  pursue  one  course  which  will  be  applicable  in  every 
case, — the  rule  generally  adopted  by  surgeons,  in  all  operations  for 
inguinal  hernise,  is  to  carry  ihe  incision  through  the  neck  of  the  sac 
directly  upwards  from  its  middle. 


FEMORAL  HERNIA. 


591 


OF  THE  PARTS  CONCERNED  IN  FEMORAL  HERNIA. 

The  hernia  distinguished  as  “ femoral”  leaves  the  abdomen  at  the 
groin,  under  the  margin  of  the  broad  abdominal  muscles,  and  upon 
the  horizontal  branch  of  the  pubes,  immediately  at  the  inner  side  of 
the  large  femoral  blood-vessels.  After  passing  downwards,  for  a very 
short  space,  about  an  inch  or  less,  the  hernia  turns  forwards  to  the 
fore  part  of  the  thigh  at  the  saphenous  opening  in  the  fascia  lata  ; and 
when  it  has  reached  this  point  the  swelling  may  be  felt  and  seen. 

The  muscles  of  the  abdomen,  beneath  the  edge  of  which  the  femoral 
hernia  escapes,  are  represented  by  the  aponeurotic  band  of  the  external 
oblique  muscle,  which  is  commonly  known  as  Poupart’s  ligament,  but 
which,  in  connexion  with  the  femoral  hernia,  is  named  \he  femoral  or 
crural  arch.  Extending  from  the  anterior  superior  spine  of  the  ilium 
to  the  pubes,  this  band  widens  at  its 
inner  end,  and,  inclining  or  folding 
backwards,  is  fixed  to  a part  of  the 
pectineal  line,  as  well  as  to  the  spine 
of  the  pubic  bone.  The  small  trian- 
gular portion  attached  to  the  pecti- 
neal line  (fig.  504)  is  known  as  Gim- 
bernat’s  ligament  (Hey).  The  outer 
edge  of  this  part  is  concave  and 
sharp;  with  other  structures,  to  be 
presently  described,  it  forms  the 
inner  boundary  of  the  aperture 
through  which  the  hernia  descends. 

The  breadth  and  strength  of  Gimber- 
nat’s  ligament  vary  in  different  bodies, 
and  with  its  breadth  varies  the  size 
of  the  opening  which  receives  the 
hernia. 

The  space  comprised  between  the  °r  crural  arch;  2,  Gimbemat’s 

femoral  arch  and  the  excavated 

margin  of  the  pelvis  is  occupied  by  the  conjoined  psoas  and  iliacus, 
with  the  anterior  crural  nerve  between  those  muscles,  and  the  external 
iliac  artery  and  vein  at  their  inner  side.  Upon  these  structures  the 
fascia  which  lines  the  abdomen  is  so  arranged  as  to  close  the  cavity 
against  the  escape  of  any  part  of  the  viscera,  except  at  the  inner  side 
of  the  blood-vessels.  But  the  arrangement  of  the  parts  situated  thus 
deeply  (towards  the  cavity  of  the  abdomen)  will  be  most  conveniently 
entered  upon  after  those  nearer  to  the  surface  shall  have  been  ex- 
amined. To  this  examination  we  now  proceed. 

The  general  disposition  of  the  superficial  fascia  met  with  on  remov- 
ing the  common  integument  from  the  groin  has  been  described  (vol.  i. 
p.  307).  In  connexion  wnth  the  present  subject,  it  will  be  enough  to 
mention  the  following  facts.  The  deeper  layer  of  this  structure  adheres 
closely  to  the  edge  of  the  saphenous  opening,  and  the  careful  removal 
of  it  is  necessary  in  order  adequately  to  display  that  aperture.  Where 
it  masks  the  saphenous  opening,  the  deep  layer  of  the  superficial  fascia 


Fig.  504. 


The  innominate  bone  of  the  left  side  with. 


592 


THE  FASCIA  LATA. 


supports  some  lymphatic  glands,  the  eflerent  vessels  of  which  pass 
through  it ; and  the  small  portion  of  the  membrane  so  perforated  is 
named  tlie  cribriform  fascia.  The  superficial  and  the  deep  fasciae  ad- 
here together  along  the  fold  of  tlie  groin  likew'ise,  and  this  connexion 
between  the  two  membranes  serves  the  purpose,  at  least,  of  drawing 
the  integument  the  more  evenly  into  the  fold  of  the  groin,  when  the 
limb  is  bent  at  the  hip  joint. 

By  Scarpa  the  deep  layer  of  the  superficial  fascia  which  covers  the  abdomen 
was  described  as  an  emanation  from  the  fascia  lata,  extended  upwards  over  the 
external  oblique  muscle.*  But  different  modes  of  viewing  the  continuity  of  such 
structures  depend  very  much  on  the  manner  of  conducting  the  dissection.  In  the 
present  case,  for  example,  the  fascia  may  be  said  to  proceed  from  above  or  from 
below,  according  as  the  parts  are  dissected  from  the  abdomen  downwards  or  from 
the  thigh  upwards.  Such  difference,  however,  is  no  more  than  a verbal  one,  the 
material  fact  being  merely  that  the  two  membranes  are  comrected  together  along 
the  groin. 

The  separation  of  the  fascia  lata  into  two  parts  at  the  saphenous 
opening,  and  the  position  and  connexions  of  each  part,  having  been 
described  in  detail  (p.  308),  only  a few  points  in  the  arrangement  of 
this  membrane  will  be  noticed  in  this  place.  At  the  lower  end  of  the 
saphenous  opening  the  iliac  division  of  the  fascia  is  continuous  w'ith 
the  pubic  by  a well-defined  curved  margin,  immediately  above  which 
the  saphenous  vein  ends;  above  the  opening  a pointed  cornu  (falciform 
process — Burns)j-  of  the  same  portion  of  the  fascia  (fig.  497),  extend- 
ing inwards  in  connexion  w'ith  the  femoral  arch,  reaches  Girnbernat’s 
ligament;  and  in  the  interval  betw'een  the  two  points  now  referred  to 
(f.  e.,  from  the  upper  to  the  lower  end  of  the  saphbnous  opening),  the 
iliac  layer  of  the  fascia  lata  blends  with  the  subjacent  sbeath  of  the 
femoral  vessels  as  well  as  with  the  superficial  fascia.  The  pubic  part 
of  the  fascia  covers  the  pectineus  muscle,  and  is  attached  to  the  pecti- 
neal ridge  of  the  pubes.  Immediately  below  the  femoral  arch  the  iliac 
and  pubic  portions  lie,  one  before,  the  other  behind,  the  femoral  blood- 
vessels and  the  sheath  of  these.  They  occupy  the  same  position  with 
respect  to  the  femoral  hernia. 

For  an  account  of  the  superficial  arteries  and  veins  which  ramify 
in  the  integument  in  the  neighbourhood  of  the  groin,  see  vol.  i.  p.  623; 
vol.  ii.  p.  25. 

The  anterior  or  iliac  part  of  the  fascia  lata  being  turned  aside,  the 
sheath  of  the  fetnoral  vessels  will  be  in  view,  fig.  499.  The  sheath  is 
divided  by  septa,  so  that  each  vessel  is  lodged  in  a separate  compart- 
ment, and  the  vein  is  separated  by  a thin  partition  from  the  artery  on 
one  side  and  from  the  short  canal  for  the  lymphatics  on  the  other  side. 
Along  the  thigh  the  sheath  is  filled  by  the  artery  and  vein,  but  be- 
hind the  femoral  arch  it  is  widened  at  the  inner  side.  Here  it  is  per- 
forated for  lymphatic  vessels,  and  on  this  account  it  is  said  to  be 

* A Treatise  on  Hernia,  translated  by  Wishart,  p.  247. 

t Edinb.  Med.  and  Surer.  Journal,  vol.  ii.  p.  26.3,  and  fig.  2. 

In  the  first  edition  of  Hey’s  Practical  Observations  in  Surgery,  the  upper  end  of  this 
process  of  the  fascia  was  named  the  “ femoral  ligament and  since  then  several  anatomists 
have  distinguished  the  same  part  as  “ Hey’s  ligament.”  But  Mr.  Hey  dropped  the  desig- 
nation in  the  subsequent  editions  of  the  same  work,  and  there  seems  no  good  reason  for 
continuing  it.  Compare  the  original  edition  (1803),  p.  151,  and  plate  4,  with  the  third 
edition  (1814),  p.  147,  and  plates  4,  5,  and  6. 


SHEATH  OF  THE  BLOOD-VESSELS. 


593 


“cribriform.”*  This  inner,  wider  part  of  the  sheath  it  is  that  receives 
the  femoral  hernia  (fig.  505) ; and  in  connexion  with  the  anatomical 
description  of  that  disease,  it  is  designated  the  femoral  canal.  At  its 


Fig.  505. 


Fig.  506. 


Fig.  505.  The  femoral  vessels  of  the  left  side,  with  their  sheath  laid  open,  and  a small  hernia 
displayed. — 1.  The  lower  part  of  the  external  oblique  muscle.  2.  The  anterior  superior  spine 
of  the  iliuni.  3.  Iliacus  muscle.  4.  Sartorius.  5.  Pubic  part  of  the  fascia  lata.  6.  Femoral 
artery.  7.  Femoral  vein.  8 A small  hernia. 

Fig.  506.  The  groin  of  the  right  side  dissected  so  as  to  display  the  deep  femoral  arch. — 1.  The 
outer  part  of  the  lemoral  arch.  1'.  Part  of  the  tendon  of  the  external  oblique  muscle,  including 
the  femoral  arch,  and  also  the  inner  column  of  the  external  inguinal  ring,  projecting  through 
which  is  seen  a portion  of  the  spermatic  cord  cut.  2.  The  lemoral  arch  at  its  insertion  into  the 
spine  of  the  pubes.  The  fibres  outside  the  numeral  are  those  of  Gimbernat’s  ligament.  3 The 
outer  part  of  the  femoral  sheath.  4.  The  spermatic  cord,  after  having  perforated  the  fascia 
transversalis.  5.  The  deep  femoral  arch — its  inner  end  where  it  is  fixed  to  the  pubes.  6.  In- 
ternal oblique  muscle.  7.  Transversalis.  Beneath  the  lower  edge  of  this  muscle  is  seen  the 
transversalis  fascia,  which  continues  into  the  femoral  sheath  under  the  deep  femoral  arch.  8. 
Conjoined  tendon  of  the  internal  oblique  and  transversalis  muscles.  9.  A band  of  tendinous 
fibres  directed  upwards  behind  the  external  abdominal  ring. 

upper  end  the  sheath  of  the  vessels  is  continuous  with  the  lining  mem- 
brane of  the  abdomen — with  the  fascia  transversalis  at  its  fore  part 
(fig.  499,  506),  with  the  fascia  iliaca  behind. 

When  the  femoral  artery  is  being  removed,  it  will  be  found  that  a 
bundle  of  fibres  (fig.  506),  springing  from  its  under  surface  outside 
the  femoral  vessels,  extends  across  the  fore  part  of  the  femoral  sheath, 
and,  widening  at  its  inner  end,  is  fixed  to  the  pecten  of  the  pubes  be- 
hind Gimbernat’s  ligament.  This  tendinous  band  is  known  as  the 
deep  femoral  arch.  Connected  with  the  same  part  of  the  pubes  is  the 
conjoined  tendon  of  the  internal  oblique  and  transverse  muscles  (fig. 
499).  The  tendon  lies  behind  the  attachment  of  the  deep  femoral 
arch  (fig.  506).  In  many  cases  the  last-named  structure  is  not 
strongly  marked ; and  it  may  be  found  to  blend  with  the  tendon 

* The  word  ‘cribriform’  being  applied  to  this  part  as  well  as  to  the  layer  of  the  super- 
ficial fascia  stretched  across  the  saphenous  opening,  the  two  structures  are  distinguished 
in  the  following  manner  : — the  former  is  known  as  the  cribriform  portion  of  the  sheath  of 
the  vessels,  while  to  the  latter  is  assigned  the  name  of  cribriform  fascia. 

‘ 50* 


694 


FEMORAL  HERNIA. 


of  t!ie  muscles  just  referred  to.  Not  unfrequently  it  is  altogether 
wanting. 

Attention  now  being  directed  to  the  internal  surface  of  the  abdo- 
men  (fig.  501): — When  the  peritoneum  has  been  removed,  it  will  be 
observed  that  the  fasciae  lining  the  cavity  form  for  the  most  part  a 
barrier  against  the  occurrence  of  hernia  ; for  outside  the  iliac  vessels 
the  fascia  iliaca  and  fascia  transversalis  are  continuous  one  with  the 
other  behind  the  femoral  arch.  These  fasciae  are,  in  fact,  but  parts 
of  the  same  membrane  to  which  diflerent  names  are  assigned  for  the 
convenience  of  description,  just  as  distinctive  names  are  applied  to 
portions  of  the  same  artery.  But  where  the  iliac  artery  and  vein 
occur,  the  arrangement  of  the  fasciae  is  different.  The  vessels  rest 
upon  the  fascia  iliaca  ; and  the  membranes,  instead  of  joining  at  an 
angle  as  elsewhere,  are  continued  into  their  sheath  in  the  manner 
above  described.* 

The  sheath  is  closely  applied  to  the  artery  and  vein,  so  that,  in  the 
natural  or  healthy  state  of  the  parts  there  is  no  space  left  for  the  for- 
mation of  a hernia  in  the  compartments  which  belong  to  those  vessels; 
but  at  the  inner  side  of  the  blood-vessels  will  be  found  a depression 
which  is  occupied  but  partially  with  the  lymphatics.  This  is  the 
femoral  ring,  the  orifice  of  the  femoral  canal. 

Femoral  ring. — After  the  removal  of  the  peritoneum,  this  opening  is 
not  at  first  distinctly  discernible,  being  covered  with  the  laminated 
cellular  membrane  (subserous)  which  intervenes  between  the  perito- 
neum and  the  walls  of  the  abdomen.  That  part  of  the  membrane 
which  covers  the  ring  was  found  by  M.  Cloquet  to  possess  in  some 
cases  considerable  density ; and,  from  being  the  only  barrier  in  this 
situation  between  the  abdomen  and  the  top  of  the  thigh,  it  was  named 
by  that  observer  the  crural  septum  (septum  crurale).  But  this  struc- 
ture is  usually  no  more  than  loose  cellular  membrane,  and  it  forms 
but  a very  slight  partition.  On  clearing  it  away,  the  ring  is  displayed 
(fig.  501).  It  is  a narrow  opening,  usually  of  sufficient  size  to  admit 
the  end  of  the  fore  finger ; the  size,  however,  varies  in  different  cases, 
and  it  may  be  said  to  increase  as  the  breadth  of  Gimbernat’s  ligament 
diminishes,  and  the  converse.  It  is  larger  in  the  female  than  in  the 
male  body.  On  three  sides  the  ring  is  bounded  by  very  unyielding 
structures.  In  front  are  the  femoral  arches  ; behind  is  the  horizontal 
branch  of  the  pubes  covered  by  the  pectineus  muscle  and  the  pubic 
layer  of  the  fascia  lata  ; on  the  outer  side  lies  the  external  iliac  vein, 
but  covered  with  its  sheath ; and  on  the  inner  side  are  several  layers 
of  fibrous  structure  connected  with  the  pectineal  line  of  the  pubes — 
namely,  Gimbernat’s  ligament,  the  deep  femoral  arch,  and  the  con- 
joined tendon  of  the  two  deeper  abdominal  muscles,  with  the  fascia 
transversalis  (fig.  506).  The  last-mentioned  structures — those  bound- 

* Some  anatomists  describe  the  sheath  of  the  vessels  as  continued  down  from  the  mem- 
branes in  llie  abdomen,  while  others  regard  it  as  an  emanation  from  the  fascia  of  the 
thigh,  but  continuous  with  the  abdominal  fascise.  As  this  difference  in  the  manner  of 
viewinsr  the  structure  in  question  does  not  alter  the  faets  in  any  way,  it  is  quite  immate- 
rial which  of  the  modes  of  description  is  adopted.  But  it  appears  to  me  most  natural  to 
regard  the  sheath  as  a production  of  the  fascia  lata. 


DESCENT  OF  HERNIA. 


595 


ing  the  ring  at  the  inner  side — present  respectively  a more  or  less 
sharp  margin  towards  the  opening. 

Femoral  canal. — From  the  femoral  ring,  which  is  its  orifice,  the 
canal  continues  downwards  behind  the  iliac  part  of  the  fascia  lata 
(its  falciform  process),  in  front  of  the  pubic  portion  of  the  same  mem- 
brane, and  ends  at  the  saphenous  opening.  It  is  about  half  an  inch  in 
length  ; but  in  its  length  the  canal  varies  a little  in  different  cases. 

Blood-vessels. — Besides  the  femoral  vein,  the  position  of  which  has 
been  already  stated,  the  epigastric  artery  is  closely  connected  with 
the  ring,  lying  above  its  outer  side.  It  not  unfrequently  happens  that 
the  obturator  artery  descends  into  the  pelvis  at  the  outer  side  of  the 
same  opening,  or  immediately  behind  it;  and  in  some  rare  cases  that 
vessel  turns  round  the  ring  to  its  inner  side.  Moreover,  an  obturator 
vein  occasionally  has  the  same  course;  and  small  branches  of  the 
epigastric  artery  will  be  generally  found  ramifying  on  the  posterior 
aspect  of  Gimbernat’s  ligament.  In  the  male  body,  the  spermatic 
vessels  are  separated  from  the  canal  only  by  the  femoral  arch. 

To  the  foregoing  account  of  the  anatomical  arrangement  of  the 
parts  concerned  in  femoral  hernia,  may  be  added  certain  measure- 
ments, showing  the  distances  of  some  of  the  most  important  from  a 
given  point.  They  are  copied  from  the  work  of  Sir  A.  Cooper  : — * 

From  the  symphysis  pubis  to  the  anterior  spine  of 

the  ilium 

From  same  point  to  the  middle  of  the  iliac  vein  . 

“ to  the  origin  of  the  epigastric 

artery 

“ to  the  middle  of  the  lunated  edge 

of  the  fascia  lata 

“ to  the  middle  of  the  femoral  ring 

Descent  of  the  hernia. — When  a femoral  hernia  is  being  formed,  the 
protruded  part  is  at  first  vertical  in  its  course  (fig.  505)  ; but  at  the 
lower  end  of  the  canal,  after  the  passage  of  about  half  an  inch,  it 
undergoes  a change  of  direction,  bending  forward  at  the  saphenous 
opening;  and,  as  it  increases  in  size,  it  ascends  over  the  iliac  part  of 
the  fascia  lata  and  the  femoral  arch.  The  hernia  thus  turns  round 
those  structures,  passing  from  behind  them  to  their  anterior  surface. 
Within  the  canal  the  hernia  is  very  small,  being  constricted  by  the 
unyielding  structures  which  form  that  passage  ; but  when  it  has  passed 
beyond  the  saphenous  opening,  it  enlarges  in  the  loose  cellular  mem- 
brane of  the  groin  ; and,  as  the  tumour  increases,  it  extends  outwards 
in  the  groin  towards  the  spine  of  the  iliac  bone.  Hence  its  greatest 
diameter  is  transverse. 

Coverings  of  the  hernia. — The  sac  which  is  pushed  before  the  pro- 
truded viscus,  is  derived  from  the  external  fossa  of  the  peritoneum  ; 
except,  however,  when  the  cord  of  the  obliterated  umbilical  artery  is 
placed  outside  its  ordinary  position,  in  which  case  the  serous  mem- 
brane furnishes  the  sac  from  its  internal  fossa  (see  page  584).  After 


Male. 

5|  inches, 


2f  “ 


Female. 

. . . 6 inches. 

. . . 2|  “ 

. . . 3i  “ 

. . . 2|  “ 

. . . 2f  “ 


* On  Crural  Hernia,  p.  5. 


596 


OPERATION  FOR  RELIEF  OF 


the  sac,  the  hernia  carries  before  it  the  subserous  cellular  membrane 
(septum  crurale  of  Cloquet),  which  covers  the  femoral  ring,  and  like- 
wise an  elongation  from  the  sheath  of  the  femoral  vessels.  These  two 
structures  combined  constitute  a single  very  thin  covering,  known  as 
the  fascia  propria  of  the  hernia  (Cooper).  It  sometimes  happens  that 
the  hernia  is  protruded  through  an  opening  in  the  sheath,  which  there- 
fore in  that  event  does  not  contribute  to  form  the  fascia  propria. 

Diagnosis.  — Passing  over  the  general  symptoms  of  abdominal 
herniae  and  the  means  of  forming  the  diagnosis  between  a hernia  and 
several  other  diseases  with  which  it  is  liable  to  be  confounded, — sub- 
jects which  fall  within  the  province  of  treatises  on  practical  surger3% 
— 1 shall  limit  the  observations  to  be  made  in  this  place  to  the  anatomi- 
cal circumstances  which  characterize  femoral  hernia,  and  serve  to 
distinguish  it  from  the  inguinal  form  of  the  complaint.  When  the 
inguinal  hernia  descends  to  the  scrotum  or  to  the  labium  pudendi,  and 
when  the  femoral  hernia  extends  some  distance  outwards  in  the  groin, 
no  error  in  diagnosis  is  likely  to  arise.  It  is  only  in  distinguishing 
between  a bubonocele  and  a femoral  hernia  of  moderate  size  that  a 
difficulty  occurs.  The  position  of  the  femoral  hernia  is,  in  most  cases, 
characteristic.  The  tumour  is  upon  the  thigh,  and  a narrowed  part, 
or  neck,  may  be  felt  sinking  into  the  thigh  near  its  middle.  Besides, 
the  femoral  arch  is  usually  to  be  traced  above  this  hernia,  while  that 
band  is  lower  than  the  mass  of  a tumour  lodged  in  the  inguinal  canal. 
At  the  same  time,  the  latter  tumour  covers  the  femoral  arch,  and  can- 
not, like  a femoral  hernia  when  it  has  turned  over  that  cord,  be  with- 
drawn from  it.  Some  assistance  will  be  gained,  in  a doubtful  case, 
from  the  greater  facility  with  which  the  tumour  emerging  at  the 
saphenous  opening  admits  of  being  circumscribed,  in  comparison  with 
the  bubonocele,  which  is  bound  down  by  a more  resistant  structure — 
the  aponeurosis  of  the  external  oblique  muscle.  Other  practical  appli- 
cations of  the  foregoing  anatomical  observations  come  now  to  be  con- 
sidered. * 

The  taxis. — During  the  efforts  of  the  surgeon  to  replace  the  hernia, 
the  thigh  is  to  be  flexed  upon  the  abdomen  and  inclined  inwards,  with 
a view  to  relax  the  femoral  arch ; the  tumour  is,  if  necessary,  to  be 
withdrawn  from  over  the  arch,  and  the  pressure  on  it  is  to  be  directed 
backwards  into  the  thigh. 

The  operation. — The  replacement  of  the  hernia  by  the  means  just 
adverted  to  being  found  impracticable,  the  operation  is  undertaken 
with  the  view  of  dividing  the  femoral  canal  (or  some  part  of  it), 
thereby  widening  the  space  through  which  the  protruding  viscus  is  to 
be  restored  to  the  abdomen,  or  with  the  view  of  relieving  strangulation 
when  the  restoration  of  the  part  is  not  possible  or  not  desirable.  Inas- 
much as  the  manner  of  conducting  the  operation  chiefly  depends  on 
the  place  at  which  the  constricting  structures  are  to  be  cut  into,  it  will 
be  convenient  in  the  first  instance  to  determine  this  point;  and  with 
this  object  we  shall  inquire  into  the  practicability  and  safety  of  making 
incisions  into  the  femoral  canal  at  different  points  of  its  circumference. 
As  the  hernia  rests  upon  the  pelvis  (the  pubes),  the  posterior  part  of 
the  canal  may  at  once  be  excluded  from  consideration ; so  likewise 


STRANGULATED  FEMORAL  HERNIA. 


597 


may  its  outer  side,  on  account  of  the  position  of  the  femoral  vein,  and 
the  outer  part  of  its  anterior  boundary  also,  because  of  the  presence 
of  the  epigastric  artery  in  this  direction.  There  remains  only  the 
inner  boundary  with  the  contiguous  part  of  tlie  anterior  one,  and 
through  any  point  of  this  portion  of  the  ring  or  canal  an  incision  of 
the  required  extent  (always  a very  short  one)  can  be  made  without 
danger  in  nearly  all  cases.  The  sources  of  danger  are  only  occasional ; 
for  the  urinary  bladder  when  largely  distended,  and  the  obturator 
artery  when  it  turns  over  the  femoral  ring — a very  unusual  course — 
are  the  only  parts  at  the  inner  side  of  the  hernia  liable  to  be  injured  ; 
while  the  last-named  vessel,  when  it  follows  the  course  just  referred 
to,  and  in  the  male  the  spermatic  cord,  are  the  structures  in  peril 
when  the  anterior  boundary  of  the  canal  is  cut  into  towards  the  inner 
side  of  the  hernia. 

Returning  now  to  the  steps  of  the  operation: — After  it  has  been 
ascertained  that  the  urinary  bladder  is  not  distended,  the  skin  is  to  be 
divided  by  a single  vertical  incision  made  on  the  inner  part  of  the 
tumour,  and  extending  over  the  crural  arch.  When  the  subcutaneous 
fat  (the  thickness  of  which  is  very  various  in  different  persons)  is  cut 
through,  a small  blood-vessel  or  two  are  divided,  and  some  lymphatic 
glands  may  be  met  wdth.  The  hemorrhage  from  the  blood-vessels 
seldom  requires  any  means  to  restrain  it ; but  the  glands,  if  enlarged, 
retard  the  operation  in  some  degree.  The  fascia  propria  of  the  hernia, 
which  succeeds  to  the  subcutaneous  fat,  is  distinguished  by  its  mem- 
branous appearance  and  the  absence  of  fat.  It  is  very  thin,  and 
caution  is  required  in  cutting  through  it,  as  the  peritoneal  sac  is 
immediately  beneath : the  two  membranes  are  indeed  in  contact, 
except  in  certain  cases  to  be  presently  noticed.  A flat  director ‘is 
now  to  be  insinuated  between  the  hernial  sac  and  the  inner  side  of  the 
femoral  canal,  space  for  the  instrument  being  gained  by  pressing  its 
smooih  surface  against  the  neck  of  the  hernia.  On  the  groove  of  the 
director  so  introduced,  or  under  the  guidance  of  the  fore-finger  of  the 
left  hand,  if  the  use  of  the  director  should  be  dispensed  with,  the  probe- 
pointed  bistoury  is  passed  through  the  canal,  and  the  dense  fibrous 
structure  of  which  it  consists  is  divided,  the  edge  of  the  knife  being 
turned  upwards  and  inwards,  or  directly  upwards.  By  the  former 
plan  of  relieving  the  stricture,  the  parts  divided  are  the  following, 
viz.,  the  falciform  process  of  the  fascia  lata  and  the  structures  fixed 
to  the  pectineal  line  of  the  pubes,  namely,  Gimbernat’s  ligament,  the 
inner  end  of  the  deep  femoral  arch,  and,  it  may  be,  the  tendon  of  the 
two  deep  abdominal  muscles  with  the  fascia  transversalis ; while  if  the 
incision  be  directed  upwards,  the  falciform  process  of  the  fascia  lata 
and  the  two  femoral  arches  are  divided.  The  opening  being  sufli- 
ciently  dilated,  the  protruded  part  is  restored  to  the  abdomen  as  in 
the  taxis. 

But  it  may  be  found  necessary  to  lay  the  hernial  sac  open  in  order 
to  examine  its  contents,  or  in  order  to  relieve  the  impediment  to  the 
return  of  the  hernia,  if  that  should  happen  to  reside  in  the  neck  of  the 
sac  itself.  In  this  case  it  will  probably  be  required  to  add  to  the 
vertical  incision  already  made  through  the  integuments  and  cellular 


698 


ISCHIO  RECTAL  REGION. 


membranes  another,  directed  outwards  over  the  tumour,  and  parallel 
with  the  lemoral  arch.  Such  additional  incision  is  readily  made,  by 
passing  the  scalpel  beneath  the  integument  and  fat,  and  cutting  out- 
wards after  the  skin  has  been  pierced  with  the  point  of  the  knife. 
The  sac  being  now  opened,  the  hernia  knife  is  used  at  the  inner  side 
of  its  neck,  while  the  bowel  is  guarded  with  the  left  hand.  During 
the  restoration  of  the  protruded  parts,  some  advantage  will  be  gained 
if  the  edges  of  the  divided  sac  should  be  held  down  with  a pair  or  two 
of  forceps  in  the  hands  of  an  assistant. 

In  the  foregoing  observations,  it  has  been  stated  that  the  fascia 
propria  is  in  contact  with  the  sac  of  the  hernia,  except  in  certain 
cases.  The  exception  is  afforded  by  the  interposition  of  fat,  and 
sometimes  in  considerable  quantity.  The  adipose  substance  is  deposited 
in  the  subserous  cellular  membrane;  it  has  the  peculiarity  of  resembling 
the  fat  lodged  in  the  omentum,  and  it  is  occasionally  studded  with 
small  cysts,  containing  a serous  fluid.  The  hernia  will  be  most  readily 
found  in  such  circumsiances  behind  the  inner  part  of  the  adventitious 
substance ; which  should  be  turned  outwards  from  the  inner  side,  or 
cut  through. 

THE  PERINEUM  AND  ISCHIO-RECTAL  REGION. 

A connected  view  of  the  structures  which  occupy  the  outlet  of  the 
pelvis  becomes  necessary,  in  consequence  of  the  important  surgical 
operations  occasionally  performed  on  the  genito-urinary  organs  and 
the  rectum,  which  are  contained  in  that  part.  In  the  examination  of 
these  structures,  which  it  is  proposed  to  make  in  this  place,  attention 
will  be  confined  to  the  male  body. 

The  pelvic  bones,  as  they  bound  the  outlet  of  the  pelvis,  are  already 
sufficiently  described  (vol.  i.  p.  205).  The  anterior  portion  of  the  space, 
which  is  appropriated  to  the  urethra  and  the  penis,  is  named  the 
'perineum.  This  part  is  triangular,  the  sides  being  formed  by  the 
branches  of  the  ischium  and  pubes  meeting  at  the  symphysis  pubis, 
while  a line  extended  between  the  two  tuberosities  of  the  ischia  repre- 
sents the  base  of  the  triangle.  In  well-formed  bodies,  the  three  sides 
of  the  space  are  equal  in  length;  but  cases  occur  in  which,  by  the 
approximation  of  the  ischiadic  tuberosities,  the  base  is  narrowed  ; 
and,  we  may  anticipate  the  practical  application  of  the  anatomical 
facts  so  far  as  to  state  here,  that  this  circumstance  exercises  a mate- 
rial influence  on  the  operation  of  lithotomy,  inasmuch  as  the  incisions 
required  in  that  operation,  instead  of  being  oblique  in  their  direction, 
must,  in  such  circumstances,  be  made  more  nearly  straight  backwards. 

That  portion  of  the  outlet  of  the  pelvis  which  lies  behind  the  peri- 
neum may  be  named  the  ischio-rectal  region.  It  contains  the  end  of 
the  rectum  ; and  it  is  defined  by  the  tuberosities  of  the  ischium,  the 
coccyx,  and  the  great  gluteal  muscles.  VVe  shall  now  proceed  to  the 
detailed  examination  of  the  two  parts  thus  mapped  out. 

The  skin  of  the  perineum  continued  from  the  scrotum,  and  partaking 
of  the  characters  it  has  on  that  part,  is  dark-coloured,  thin,  and  exten- 
sible, loosely  connected  with  the  subjacent  textures,  and  in  the  male 
body  studded  with  crisp  hairs.  Around  the  anus,  it  is  thrown  into 


THE 'PERINEUM. 


599 


folds,  which  are  necessary  to  allow  the  extension  of  the  orifice  of  the 
bowel,  during  the  passage  of  masses  of  fascal  matter;  and  along  the 
middle  of  the  perineum  the  median  ridge  or  raphe  of  the  scrotum  is 
continued  backwards  to  the  anus.  By  this  mark  upon  the  skin,  the 
large  triangle  in  which  is  comprised  the  whole  perineum,  is  subdivided 
into  two  equal  parts.  To  one  of  these  smaller  spaces  the  operations 
usually  performed  for  gaining  access  to  the  urinary  bladder  are  for 
the  most  part  restricted.  The  skin  of  the  perineum  is  provided  with 
numerous  sebaceous  follicles. 

From  the  muscles  of  the  perineum,  the  skin  is  separated  by  cellular 
membrane  and  fat,  except  in  the  neighbourhood  of  the  anus,  where 
the  sphincter  of  the  bowel  is  immediately  in  contact  with  the  integu- 
ment. The  deeper  part  of  the  fatty  cellular  membrane, — the  superficial 
fascia  (see  p.  304), — taking  on  a membranous  appearance,  has,  in  a 
great  measure,  the  same  arrangement  and  characters  as  the  corre- 
sponding structure  of  the  groin.  With  that  membrane  the  perineal 
fascia  is  continuous  in  front  through  the  scrotum,  but  at  other  points 
it  is  confined  to  the  perineum,  being  fixed  laterally  to  the  branches  of 
the  ischium  and  the  pubes  (fig.  507),  while  it  is  continued  posteriorly 
into  the  deep  perineal  fascia,  beneath  the  sphincter  ani  and  in  front  of 
the  rectum.  It  is  in  consequence  of  these  connexions  of  the  superficial 
fascia  of  the  perineum,  that  abscesses  do  not  attain  a large  size  in 
the  perineum,  and  that  urine  effused  in  consequence  of  rupture  of  the 
urethra  does  not  extend  backwards  to  the  rectum  or  outwards  to  the 
thigh,  but  continues  forward,  and,  if  an  outlet  for  its  escape  should  not 
be  afforded  by  the  surgeon,  reaches  successively  the  scrotum,  the 


Tlie  perineum  and  part  of  the  thighs  after  the  skin  and  a portion  of  the  superficial  fascia  had 
been  removed. — a.  Superficial  fascia,  b.  Accelerator  urinas.  c.  Erector  penis,  d.  Transversus 
perinei.  e.  Upper  point  of  sphincter  ani.  /.  The  edge  of  the  glutmus  maxiraus.— 1.  Superficial 
perineal  artery.  2.  Superficial  perineal  nerve. 


Fig.  507. 


GOO 


THE  PERINEUM. 


penis,  and  the  groin  above  Poupart’s  ligament.  In  extreme  cases  the 
exlravasated  fluid  would  spread  from  the  position  last  mentioned  over 
the  anterior  part  of  the  abdomen  and  even  to  the  thorax,  its  extension 
downwards  to  the  thigh  being  restrained  by  the  attachm.ent  of  the 
superficial  fascia  along  the  fold  of  the  groin. 

The  muscles  brought  into  view  by  the  removal  of  the  superficial 
fascia  are,  on  each  side,  the  accelerator  urinse,  erector  penis,  and 
transversus  perinei  (fig.  507).  Between  these  muscles  is  a depression, 
in  which  access  may  be  gained  to  the  membranous  part  of  the  urethra, 
without  wounding  the  erectile  tissue  of  the  penis,  namely,  the  corpus 
spongiosum  urethrm  with  its  bulbous  enlargement  on  the  one  hand, 
and  the  crus  of  the  corpus  cavernosum  on  the  other,  covered  respec- 
tively by  the  accelerator  urinse  and  the  erector  penis.  Along  this 
depression  is  placed  the  superficial  artery  of  the  perineum,  with  the 
accompanying  nerve,  and  the  transverse  artery  crosses  behind  it ; at 
the  bottom  of  the  depression,  after  the  muscular  structure  has  been 
turned  a little  aside,  the  deep  perineal  fascia  is  met  with. 

The  last-named  membrane,  deep  perineal  fascia  (see  page  305),  fills 
the  space  between  the  rami  of  the  ischium  and  pubes,  and  is  therefore 
necessarily  triangular  in  shape  (fig.  509).  It  consists  of  two  laminae  of 
fibrous  membrane  (fig.  510,  b),  the  anterior  being  much  the  thicker  and 
more  tendinous  of  the  two.  The  layers  are  separated  by  an  interval, 
in  which  the  compressor  muscles  of  the  urethra  (vol.  ii.  p.  538)  are  lodged, 
together  with  Cowper’s  glands  and  the  arteries  of  the  bulb,  as  well  as 
the  pudic  arteries  and  nerves  for  a short  space  (fig.  508).  Where  it 


Fig-.  508. 


A deeper  dissection  thon  that  represented  in  the  last  figure,  the  perineal  muscles  being 
removed  and  also  the  fat  in  the  ischio-recial  fossa. — a.  Superficial  fascia,  h.  Accelerator  urinae. 
c.  Crus  penis,  d.  The  bulb.  e.  Triangular  ligament  of  ureihra.  /.  Levator  ani.  g-.  Sphincter. 
h.  Tuberosity  of  ischium,  k.  Gluteus  maximus.  * Cowper’s  gland  of  the  left  side.  1.  Pudic 
artery.  2.  Superficial  perineal  artery  and  nerve.  The  inferior  hemorrhoidal  arteries  and  the 
artery  of  the  bulb  are  likewise  shown. 


THE  PROSTATE. 


601 


is  perforated  by  the  membranous  portion  of  the  urethra,  the  fore  part 
of  the  deep  perineal  fascia  is  continuous  with  the  fibrous  cover  of  the 
bulb  and  corpus  spongiosum  urethrae,  so  that  the  fascia  does  not  pre- 
sent a defined  edge  to  the  tube  which  passes  through  it.  The  poste- 
rior layer  is  connected  with  the  capsule  of  the  prostate  gland. 

The  anterior  of  the  two  layers  here  and  elsewhere  in  this  work  (vol.  i.  p.  305) 
noticed  as  constituting  the  deep  perineal  fascia,  is  that  which  alone  forms  the 
triangular  ligament  of  the  urethra.  (See  especially  Camper,  Demonstrationes  Ana- 
tomico-Pathologicae.)  It  is  that  layer  which,  being  pierced  by  the  urethra,  inter- 
feres with  -the  passage  of  instruments  along  the  canal.  Moreover,  it  is  the  only 
part  of  the  structure  recognised  by  most  anatomical  writers.  The  slip  of  mem- 
brane described  as  the  posterior  layer  of  the  deep  fascia^  in  accordance  with  the 
plan  which  appears  to  be  now  generally  received  in  this  cpuntry  (Colles’  “ Sur- 
gical Anatomy,”  p.  191;  Harrison,  “Dublin  Dissector,”  vol.  i.  p.  315;  Guthrie 
“On  the  Neck  of  the  Bladder,”  &c.,  p.  41),  might  be  regarded  as  a dependency 
of  the  membranes  lining  the  pelvis. 

The  structure  next  met  with  in  examining  the  perineum,  is  the  leva- 
tor ani  (its  fore  part)  figs.  509,  511,  and  immediately  under  that  muscle 


[Fig.  509. 


The  pubic  arch  with  the  attachment  of  the  perineal  fascise.  1,  1,  1.  The  superficial  perineal 
fascia  divided  by  a ^ shaped  incision  into  three  flaps;  the  lateral  flaps  are  turned  over  the  ramus 
of  the  os  pubis  and  ischium  at  each  side,  to  which  they  are  firmly  attached  ; the  posterior  flap  is 
continuous  with  the  deep  perineal  fascia.  2.  The  deep  perineal  fascia.  3.  The  opening  for  the 
passage  of  the  membranous  portion  of  the  urethra,  previously  to  entering  the  bulb.  4.  Two  pro- 
jections of  the  anterior  layer  of  the  deep  perineal  fascia,  corresponding  with  the  position  of 
Cowper’s  glands. — W.] 

is  the  prostate.  Placed  before  the  neck  of  the  bladder,  around  the  ure- 
thra, behind  and  below  the  arch  of  the  pubes,  and  above  the  rectum, 
the  prostate  is  supported  by  the  levator  ani  and  the  pelvic  fascia, — the 
latter  dropping  down  from  the  pubes  on  its  base.  It  is  invested  with 
a fibrous  covering,  and  on  this  account  the  outer  surface  does  not 
readily  yield  to  a cutting  instrument,  while  the  proper  substance  of  the 
gland  is  cut  or  lacerated  with  comparative  facility.  From  the  increase 
of  its  breadth  towards  the  lower  surface,  it  follows  that  the  greatest 
VOL.  II.  51 


602 


THE  PERINEUM. 


extent  of  incision  from  the  urethra,  without  wholly  dividing  the  gland, 
would  be  made  in  a direction  outwards  and  backwariis. 


Fig.  510. 


The  pelvic  viscera  of  the  male  seen  on  the  left  side. — 1.  The  body  of  the  left  pubes  sawed 
through.  2.  Corpus  cavernosum  penis.  2'.  Corpus  spongiosum.  3.  Proslate  gland,  with  a por- 
tion of  the  levator  ani  covering  its  fore  part.  4.  Urinary  bladder.  5.  Intestinum  rectum.  6. 
Deep  perineal  fascia — its  two  layers.  7.  Cut  edge  of  (he  pelvic  fascia  extending  from  the  pubes 
to  the  back  part  of  the  prostate.  8.  Vas  deferens.  8'.  Vesicula  seminalis.  9.  Ureter.  The  cut 
edge  of  the  peritoneum  is  seen  jagged  over  the  bladder  and  the  rectum. 

The  examinalion  of  the  prostate  by  the  surgeon  is  made  through 
the  rectum.  It  is  only  through  the  gut  that  it  can  be  felt.  When  the 
gland  is  enlarged,  as  it  commonly  is  in  aged  persons,  the  urethra  is 
raised  above  its  natural  level  and  elongated.  But  the  augmentation  of 
size  may  be  partial,  affecting  one  lateral  lobe  (a  rare  occurrence)  and 
then  the  urethra  is  inclined  to  one  side;  or  the  middle  and  posterior 
part  or  middle  lobe  may  be  projected  upwards  at  the  orifice  of  the 
urethra,  so  as  even  to  obstruct  the  escape  of  the  urine  from  the  blad- 
der. In  this  last  case,  the  point  of  the  instrument  passed  along  the 
urethra,  must  be  inclined  upwards  more  than  is  required  in  the  healthy 
condition  of  the  parts,  in  order  that  it  may  be  made  to  enter  the 
bladder  over  the  projection  referred  to.  The  part  of  the  urethra 
encircled  by  the  prostate  admits  of  considerable  dilatation.  For  the 
position  of  the  seminal  and  other  openings  into  it,  reference  may  be 
made  to  the  description  of  the  canal  at  page  534,  vol.  ii. 

Behind  the  prostate  the  neck  of  the  urinary  bladder  presents  itself. 
Here  the  bladder  is  bound  to  the  pubes  at  its  upper  part  by  tbe  pelvic 
fascia,  the  bands  of  which  are  named  its  anterior  and  lateral  liga- 
ments. Laterally  the  fascia  reaches  the  organ  in  question  over  the 
base  of  the  prostate,  (fig.  511);  and  an  elongation  from  the  same  mem- 
brane extends  from  side  to  side  between  the  bladder  and  the  rectum 
after  investing  the  vesiculas  seminales  and  vasa  deferentia. 

Turning  attention  in  the  next  place  to  the  rectum,  which  occupies 
the  irregularly-shaped  space  behind  the  perineum,  we  shall  recall  a 
few  particulars  respecting  it.  The  lowest  or  third  division  of  the 
bowel,  which  measures  about  an  inch  and  a half  in  length,  is  directed 
obliquely  backwards  from  the  fore  part  of  the  prostate  to  the  anus  (fig. 


THE  RECTUM. 


603 


511) ; and  as  at  the  same  time  the  urethra  here  inclines  forwards  with 
the  penis,  the  space  between  the  two  widens  towards  the  surface  of  the 
peritoneum.  Into  this  space  the  bulb  of  the  corpus  spongiosum  drops 
down  occupying  it  more  or  less  according  as  the  erectile  tissue  is  more 
or  less  distended.  The  part  of  the  rectum  now  under  consideration  nar- 
rows to  its  end  under  the  influence  of  the  sphincters.  It  is  supported 
by  the  levatores  ani,  which  are  fixed  to  its  sides,  and  by  the  pelvic 
fascia  on  the  inner  surface  of  those  muscles. 

From  this  its  shortest  and  narrowest  part,  the  intestine  sweeps  into 
the  hollow  of  the  sacrum,  widening  considerably  at  the  same  time  so 
as  to  form  a large  pouch  (fig.  511).  This  part,  which  is  known  as 
the  second  division  of  the  rectum,  has  before  it  the  prostate  and  the 
urinary  bladder  with  the  seminal  vesicles,  and  above  these  the  recto- 
vesical pouch  of  the  peritoneum.  The  rectum  and  the  bladder  are  in 
contact  one  with  the  other,  only  in  the  small  triangular  space  inter- 
cepted between  the  seminal  vesicles  and  the  peritoneum  (fig.  512) ; and 


Fig.  511. 


Besides  the  superficial  fascia  and  the  perineal  muscles,  by  the  removal  of  which  the  spongy 
erectile  tissue  and  the  crura  penis  were  uncovered,  the  anterior  layer  of  the  deep  perineal  fascia 
was  cut  away  in  the  preparation  for  this  sketch,  and  thus  the  pudic  arteries,  with  their  branches 
for  the  bulb,  and  Covvper’s  glands  have  been  laid  bare.  The  rectum  too  having  been  dissected 
from  its  connexions  and  drawn  back,  the  prostate  gland,  the  seminal  vesicle.s,  and  part  of  the 
urinary  bladder  have  been  brought  into  view. — 1,  Fascia  lata  covering  the  adductor  muscles  of 
the  thigh.  2.  Gluteus  maximus.  3.  Rectum.  4 Crus  penis  of  left  side.  5.  Corpus  spongiosum 
urethrae.  6.  Prostate.  7.  V'esicula  seininalis  and  vas  deferens  of  left  side.  8.  A small  part  of 
urinary  bladder.  9.  Right  dorsal  artery,  with  the  artery  of  the  bulb  and  Cnwper’s  gland  resting 
against  the  inner  layer  of  the  deep  perineal  fascia.  The  last-named  parts  are  at  considerable 
depth,  but  the  size  within  which  it  was  necessary  to  restrict  the  drawing,  did  not  admit  of  the 
appearance  of  depth  being  sufficiently  preserved  in  this  representation. 

in  this  space  the  bladder  may  be  punctured,  in  order  to  evacuate  its 
contents.  In  performing  the  operation,  the  chief  guide  to  the  surgeon 
is  the  prostate.  The  instrument  is  to  be  passed  forward  into  the 
bladder  behind  this  gland;  but  care  must  be  taken  to  regulate  the  dis- 
tance from  its  margin,  so  as  to  avoid  wounding  on  the  one  hand  the 
vasa  deferentia  which  come  into  apposition  one  with  the  other  imme- 
diately behind  it ; and,  on  the  other  hand,  the  peritoneum  where  this 
membrane  turns  from  one  of  the  organs  to  the  other.  At  the  same 


604 


LITHOTOMY. 


time  it  is  to  be  remembered,  that  by  the  inclination  of  the  trocar  to 
either  side,  the  seminal  vesicles  would  be  endangered.  The  part  of 
the  intestine  now  under  observation  rests  against  the  conjoined  leva- 
tores  ani,  the  coccyx,  and  the  sacrum. 

The  lower  end  of  the  rectum  receives  small  arteries  on  each  side  from 
thepudic  (fig.  508) ; but  its  principal  artery  (the  superior  hmmorrhoidal, 
the  continuation  of  the  inferior  mesenteric)  is  placed  behind  the  organ 
and  gives  branches  to  each  side.  The  larger  branches  do  not  extend 
within  reach  of  a forefinger  of  ordinary  length.  The  veins,  like  those 
of  the  abdomen  generally,  are  without  valves.  These  vessels  are  very 
liable  to  enlarge  and  become  varicose  ; and  this  condition  is  constantly 
associated  with,  or  even  forms,  a great  part  of  the  disease  known  as 
haemorrhoids. 

Ischio-rectal  fossa. — On  each  side  of  the  rectum  between  it  and  the 
ischium  is  contained  a considerable  quantity  of  fat,  the  space  which  it 
occupies  being  named  the  ischio-rectal  fossa.  This  hollow  extends 
backwards  from  the  perineum  to  the  great  glutseal  muscle,  and  is 
bounded  on  the  inner  side  by  the  levator  ani  as  this  muscle  descends 
to  support  the  intestine,  on  the  opposite  side  by  the  obturator  fascia 
and  muscle  supported  by  the  ischium.  At  the  outer  side  and  encased 
in  a sheath  of  the  obturator  fascia  is  the  pudic  artery  with  the  accom- 
panying veins  and  nerve;  and  small  offsets  from  these  cross  the  fossa 
to  supply  the  lower  end  of  the  rectum.  The  pudic  artery,  it  will  be 
observed,  is  about  an  inch  above  the  lower  surface  of  the  tuber  ischii, 
and  at  the  same  time,  by  its  position  under  that  prominence  of  the 
bone,  it  is  protected  from  injury  by  incisions  directed  backwards  from 
the  perineum ; but  in  front  of  this  part,  in  the  perineum,  inasmuch  as 
the  vessel  lies  along  the  inner  margin  of  the  branches  of  the  ischium 
and  pubes,  it  is  here  liable  to  be  wounded  when  the  deeper  structures 
of  the  perineum  are  incised. 

The  fossa  is  narrowed  as  it  reaches  upwards  into  the  pelvis;  such 
narrowing  of  the  space  is  the  necessary  result  of  the  direction  of  the 
levator  ani,  which  drops  inwards  from  the  fascia  on  the  side  of  the 
pelvis,  and  thus  limits  the  fossa  at  its  upper  end. 

LATERAL  OPERATION  OF  LITHOTOMY. 

The  intention  of  the  operation,  as  it  is  usually  performed,  is  to  re- 
move a calculus  from  the  urinary  bladder  by  an  opening  made  through 
the  perineum  and  the  prostatic  part  of  the  urethra.  The  incisions  to 
attain  this  end  are  commonly  made  on  the  left  half  of  the  perineum, 
because  this  side  is  most  convenient  to  the  right  hand  of  the  operator ; 
but,  if  the  surgeon  should  operate  with  the  left  hand,  then  the  opposite 
(right)  side  of  the  perineum  would  be  most  convenient. 

The  position  at  which  the  perineum  is  to  be  incised  requires  careful 
consideration.  For  if  the  necessary  incisions  should  be  made  too 
near  the  middle  line  of  the  body,  the  bulbous  enlargement  of  the  corpus 
spongiosum  ureihrfs  and  the  rectum  are  liable  to  be  wounded  ; and  if, 
on  the  other  hand,  the  perineum  should  be  divided  towards  its  outer 
boundary  (the  conjoined  branches  of  the  pubes  and  ischium),  there  is 
a risk  of  wounding  the  pudic  artery  where  that  vessel  has  reached  the 


LITHOTOMY. 


G05 


inner  edge  of  the  bone.  The  incisions  are  therefore  to  be  made 
through  the  area  of  the  small  perineal  space  in  such  manner  as  to 
avoid  both  its  sides.  Again,  as  to  the  length  to  which  the  several 
structures  are  to  be  incised  : — The  integument  and  the  subcutaneous 
cellular  membrane  must  be  divided  with  freedom,  because,  1st,  the 
skin  does  not  admit  of  dilatation  during  the  removal  of  the  foreign 
body ; and  2dly,  extensive  incisions  through  the  structures  near  the 
surface  facilitate  the  egress  of  urine,  which,  after  the  operation,  con- 
tinues for  a time  to  trickle  from  the  bladder.  But  the  prostate  and  the 
neck  of  the  bladder,  on  the  contrary,  are  to  be  incised  in  but  a small 
extent.  The  reasons  for  this  rule  may  be  stated  as  follows : — By 
accumulated  experience  in  operations  on  the  living  body,  it  has  been 
found  that  the  structures  now  under  consideration  when  slightly  cut 
into  admit  of  dilatation,  so  as  to  allow  the  passage  of  a stone  of  con- 
siderable size,  and  that  no  unfavourable  consequence  follows  from  the 
dilatation.  Moreover,  when  these  parts  are  freely  divided  (cut  through), 
the  results  of  lithotomy  are  less  favourable  than  in  the  opposite  circum- 
stances. The  less  favourable  results  adverted  to  appear  to  be  due  to 
the  greater  tendency  to  infiltration  of  urine  in  the  cellular  membrane 
of  the  pelvis ; and  the  occurrence  of  this  calamity  probably  depends 
on  the  fact  that  when  the  prostate  has  been  fully  cut  through,  the 
bladder  is  at  the  same  time  divided  beyond  the  base  of  the  gland,  and 
the  urine  then  is  liable  to  escape  behind  the  pelvic  fascia  (which  it  will 
be  remembered  is  connected  with  both  those  organs  at  their  place  of 
junction)  ; whereas  if  the  base  of  the  gland  should  be  left  entire  the 
bladder  beyond  it  is  likewise  uninjured,  and  the  urine  passes  forward 
through  the  external  wound. 

The  steps  of  the  operation  by  which  the  foregoing  general  rules  are 
sought  to  be  carried  out  are  the  following  : — The  grooved  stafi’ having 
been  passed  into  the  bladder  (and  this  instrument  ought  to  be  of  as 
large  size  as  the  urethra  will  admit),  and  the  body  or  the  patient,  as 
the  case  may  be,  having  been  placed  in  the  usual  position — by  which 
position  the  perineum  is  brought  fully  before  the  operator  with  the 
skin  stretched  out — the  first  incision  is  begun  about  two  inches  before 
the  anus,  a little  to  the  left  of  the  raphe  of  the  skin,  and  from  this  point 
it  is  carried  obliquely  backwards  in  a line  about  midway  between 
the  tuber  ischii  and  the  anus,  extending  a little  way  behind  the  level 
of  the  latter.  During  the  incision,  the  knife  is  held  with  its  point 
to  the  surface,  and  it  is  made  to  pass  through  some  of  the  subcutaneous 
cellular  membrane  as  well  as  the  skin.  Now,  the  edge  of  the  knife  is 
applied  to  the  bottom  of  the  wound  already  formed,  in  order  to  extend 
it  somewhat  more  deeply;  and  the  forefinger  of  the  left  hand  is  passed 
firmly  along  for  the  purpose  of  separating  the  parts  still  further,  and 
pressing  the  rectum  inwards  and  backwards  out  of  the  way.  Next, 
with  the  same  finger  passed  deeply  into  the  wound  from  its  middle 
and  directed  upwards,  the  position  of  the  staff  is  ascertained  and  the 
structures  still  covering  that  instrument  are  divided  with  slight  touches 
of  the  knife, — the  finger  piressing  the  while  against  the  point  at  which 
the  rectum  is  presumed  to  be.  When  the  knife  has  been  inserted  into 
the  groove  of  the  staff  (and  it  reaches  that  instrument  in  the  membra- 

51* 


606 


LITHOTOMY. 


nous  part  of  the  urethra)  it  is  pushed  onwards  through  the  prostatic 
portion  of  the  canal  with  the  edge  turned  to  the  side  of  the  prostate, 
outwards,  or,  better,  outwards  with  an  inclination  backwards.  The 
knife  being  now  withdrawn,  the  forefinger  of  the  left  hand  is  passed 
along  the  staff  into  the  bladder.  With  the  finger  the  parts  are  dilated, 
and  with  it,  after  the  staff  has  been  withdrawn,  the  position  of  the 
stone  is  determined  and  the  forceps  is  guided  into  the  bladder. 

In  case  the  calculus  is  known  to  be  of  more  than  a moderate  size 
and  the  knife  used  is  narrow,  the  opening  through  the  side  of  the  pro- 
state may  be  enlarged  as  the  knife  is  withdrawn,  or  the  same  end  may 
be  attained  by  increasing  the  angle  which  that  instrument,  while  it  is 
being  passed  onwards,  makes  with  the  outer  part  of  the  staff.  And  if 
the  stone  should  be  of  large  size,  it  will  be  best  to  notch  the  opposite 
side  of  the  prostate  likewise  before  the  forceps  is  introduced.  The 
same  measure  may  be  resorted  to  afterwards  should  much  resistance 
be  experienced  when  the  foreign  body  is  being  extracted.  Lastly,  this 
part  of  the  operation  (the  extraction  of  the  stone)  should  be  conducted 
slowly,  so  as  gradually  to  dilate  the  parts  without  lacerating  them ; 
and  the  forceps  should  be  held  with  its  blades  one  above  the  other. 

The  Structures  divided  in  the  Operation. — In  the  first  incision  the 
integument  and  the  subjacent  cellular  membrane  are  divided ; after- 
wards a small  part  of  the  accelerator  urinae,  and  the  transversus 
perintei  with  the  transverse  artery.  Then  the  deep  perineal  fascia 
with  the  muscular  fibres  between  its  layers,  the  membranous  part  of 
the  urethra,  the  prostatic  part  of  the  canal,  and,  to  a small  extent,  the 
prostate  itself,  are  successively  Incised. 

The  blood-vessels : their  relation  to  the  incisions. — The  transverse 
artery  of  the  perineum,  with,  it  may  be,  the  superficial  artery  of  the 
perineum,  is  the  only  artery  necessarily  cut  through  when  the  vessels 
have  their  accustomed  arrangement;  for  in  such  circumstances  the 
artery  of  the  bulb  is  not  endangered  if  the  knife  be  passed  into  the 
staff  in  a direction  obliquely  upwards,  the  artery  being  anterior  to  the 
groove  of  that  instrument;  neither  is  there  a risk  of  wounding  the 
pudic  artery,  unless  the  incisions  through  the  deep  parts  (the  prostate 
for  instance)  should  be  carried  too  far  outwards.* 

But  in  some  cases  the  arteries  undergo  certain  deviations  from  their 
accustomed  arrangement,  whereby  they  are  rendered  liable  to  be 
wounded  in  the  operation.  Thus,  the  artery  of  the  bulb  when  it  arises, 
as  occasionally  happens,  from  the  pudic  near  the  tuber  ischii,  crosses 
the  line  of  incision  made  in  the  operation. f The  arterial  branches 
ramifying  on  the  prostate  are  in  some  instances  enlarged,  and  become 
a source  of  hemorrhage  ;J  and  the  veins  too  on  the  surface  of  that 

* For  reference  to  some  cases  in  which  the  pudic  artery  was  divided  in  lithotomy,  see 
Mr.  Crosse’s  “ Treatise  on  Urinary  Calculus,”  p.  21.  London,  183.5. 

t “ The  Anatomy  of  the  Arteries,”  <&c.,  by  R.  Quain,  p.  442,  and  plate  G4,  figs.  1 and  2. 
A case  in  which  death  resulted  from  division  of  the  artery  of  the  bulb  is  recorded  by  Dr. 
Kerr,  in  tlie  “ Edinb.  Med.  and  Surg.  Journal,”  July,  1847,  p.  155. 

t See  an  essay,  entitled  “ Remarks  on  tbe  Sources  of  Hemorrhage  after  Lithotomy,”  by 
James  Spense,  in  tlie  “ Edinburgh  Monthly  Journal  of  Medical  Science,”  vol,  i.  p.  166; 
1841.  And  “ The  Arteries,  &.C.,  by  R.  Quain,”  p.  445. 


THE  PERINEUM. 


607 


gland,  when  augmented  in  size,  may  give  rise  to  troublesome  bleed- 
ing.* Lastly,  it  should  be  added  that  the  occasional  artery  (accessory 
pudic)  which  takes  the  place  of  the  pudic  when  defective,  inasmuch 
as  it  lies  on  the  posterior  edge  of  the  prostate,  would  be  divided  if  the 
gland  were  cut  through  to  its  base,  and  only  in  this  event.f 

* “ The  Arteries,  &c.,  by  R.  Quain,”  p.  446,  and  plate  65,  6g.  3. 

t Ibid.  p.  444,  and  plate  63.  An  instance  in  which  fatal  consequences  resulted  from  the 
division  of  such  an  artery  has  been  placed  on  record.  See  “ Case  of  Lithotomy  attended 
with  Hemorrhage,  by  J.  Shaw,  Esq.,”  in  “ The  London  Medical  and  Physical  Journal,” 
vol.  Iv.  p.  3,  with  a figure.  1826. 


INDEX 


Abdomen,  ii.  443. 
regions  of,  ii.  444. 
viscera  of,  ii.  445. 

position  of,  ii.  505. 

Aberrant  duct  of  testis,  ii.  551. 
ducts  of  liver,  ii.  475. 

Absorbent  glands,  see  Glands  Lymphatic, 
system,  see  Lymphatic  system,  ii.  44. 

Absorbents,  ii.  44.  (.See  Lymphatics.) 

Accelerator  urinae,  ii.  514. 

Accessory  organs,  see  Particular  organs. 

Acervulus  cerebri,  ii.  222. 

Acetabulum,  i.  198. 

Acini  of  glands,  ii.  102. 

Acromion,  i.  176. 

Actions  of  muscles,  see  Particular  muscles. 

Adipose  tissue,  ii.  71. 

Air-cells,  ii.  117. 

capillaries  of,  ii.  120. 
structure  of,  ii.  117. 

tubes,  seeTrachea,  Bronchi,  and  Bronchia. 

Alae  nasi,  ii.  398. 

vespertilionis,  ii.  563. 

Albumen,  i.  43,  505. 

Albuminoid  compounds,  i.  43. 

principles,  chief  characters  of,  i.  43. 

Allantois,  ii.  569. 

Alveoli,  i.  139,  149. 

of  mucous  membrane,  ii.  82. 
of  stomach,  ii.  450. 

Amphiarthrosis,  i.  248. 

Ampulla  of  labyrinth,  ii.  388. 
membranous,  ii.  392. 

Amygdalae,  ii.  436. 

(cerebellum),  ii.  226. 

Anastomoses  of  arteries,  i.  637. 
veins,  ii.  5. 

Anatomy,  object  of,  i.  38. 

Anfractuosities,  ii.  202. 

Annular  protuberance,  ii.  201. 

Annulus  albidus,  ii.  365. 
ovalis,  i.  474. 

Ansae  Vieussenii,  ii.  345. 

Anti-helix,  ii.  374. 

Anti  tragus,  ii.  374. 

Antrum  of  Highmore,  i.  140,  163. 

Antrum  pylori,  ii.  447. 

Anus,  ii.  469. 

muscles  of,  ii.  469. 

Aorta,  i.  526. 

abdominal,  i.  595. 
ascending,  i.  528. 
bifurcation  of,  i.  605. 
descending,  i.  593. 
development  of,  i.  488. 
thoracic,  i.  593. 

Apertura  scalae  vestibuli,  ii.  388. 
naris,  ii.  399. 

Aponeuroses,  i.  232,  292. 
particular,  see  Fasciae. 


Aponeuroses,  abdominal,  i.  415,  301. 
vertebral,  i.  373. 

Apophyses,  i.  72. 

Appendages,  auricular,  i.  473,  478. 
of  eye,  ii.  358. 

Appendices  epiploicae,  ii.  463. 

of  auricles  of  heart,  i.  473,  478. 

Appendix  vermiformis,  ii.  462. 
vesicas,  ii.  523. 

Aqueduct  of  cochlea,  i.  127,  ii.  390. 

Fallopius,  i.  126,  ii.  379. 

Sylvius,  ii.  222. 
vestibule,  i.  126,  ii.  387. 

Aqueous  humour,  ii.  370. 

Arachnoid  membrane,  ii.  251. 

Arbor  vitae,  ii.  228. 
uterinus,  ii.  561. 

Arch  of  aorta,  i.  527. 

branches  of,  i.  531. 
of  colon,  i.  462. 
crura,  ii.  591. 

deep,  ii.  593. 
femoral,  ii.  591. 
deep,  H.  593. 

palmar,  superficial,  i.  586. 

deep,  i.  592. 
plantar,  i.  633,  636. 
pubic,  i.  205. 
zygomatic,  i.  157. 

Arches,  palatine,  i.  365,  ii.  435. 

Arciform  fibres,  ii.  201. 

Areola,  ii.  574. 

Arteriae  helicinae,  ii.  532. 
receptaculi,  ii.  553. 

Arteries,  general  anatomy  of,  i,  512. 
anastomoses  of,  i.  582,  637. 
cellular  tunic  of,  i.  515. 
coat  of,  external,  i.  515. 
internal,  i.  514. 
middle,  i.  515. 
contractility  of,  i.  516. 
differences  of,  i.  515. 
distribution  of,  i.  512. 
elastic  coat  of,  i.  514. 
fenestrated  membrane  of,  i.  514. 
nerves  of,  i.  516. 
physical  properties  of,  i.  513. 
rete  mirabile  of,  i.  513. 
sheath  of,  i.  513. 
structure  of,  i.  513. 
terminations  of,  i.  524. 
tonicity  of,  i.  516. 
tortuosity  of;  i.  513. 
vessels  of,  1.  516. 
vital  properties  of,  i.  516. 
or  Artery,  Descriptive  Anatomy  of,  i.  526. 
acromial,  i.  569,  575. 
alveolar,  i.  549. 
anastomotic,  of  arm,  i.  582. 
of  thigh,  i.  622. 


tilO 


INDEX. 


Arteries,  anastomotica  magna,  i.  625. 
angular,  efface,  i.  544. 
aorta,  see  Aorta,  i.  526. 
articular,  knee,  inferior,  i.  629. 
superior,  i.  629. 
azygos,  i.  629. 
hip,  i.  624. 

auditory,  internal,  ii.  393. 
auricular  anterior,  i.  547. 

posterior,  i.  516. 
axillary,  i.  573. 
azygos,  of  knee,  i.  629. 
basilar,  i.  566. 
brachial,  i.  578. 
brachio-cephalic,  i.  534. 
bronchial,  i.  593. 
buccal,  i.  549. 
of  bulb,  i.  615. 
capsular,  i.  601. 

of  eye,  ii.  372. 
carotid  common,  i.  534. 
external,  i.  538. 
branches  of,  i.  539. 
internal,  i.  551. 
carpal  ulnar  anterior,  i.  586. 
posterior,  i.  586. 
radial  anterior,  i.  590. 
posterior,  i.  590. 
central  of  retina,  i.  554,  ii.  370. 
cerebellar,  anterior,  i.  566. 
inferior,  i.  566. 
superior,  i.  566. 
cerebral,  anterior,  i.  555. 
middle,  i.  555. 
posterior,  i.  566. 
cervical  ascending,  i.  568. 

Artery,  cervical  princeps,  i.  545. 

profunda,  or  deep,  i.  572. 
superficial,  i.  569. 
choroid,  ii.  364. 

posterior,  i.  555. 
of  eye,  ii.  364. 
ciliary,  i.  554,  ii.  367. 
circumflex,  of  arm,  anterior,  i.  577. 
posterior,  i.  577. 
iliac,  i.  626. 

superficial,  i.  623. 
of  thigh,  external,  i.  624. 
internal,  i.  624. 
coccygeal,  i.  616. 
cochlear,  ii.  393. 
coeliac  (axis),  i.  596. 
colic,  left,  i.  600. 
middle,  i.  600. 
right,  i.  600. 

comes  nervi  ischiadici,  i.  616. 
phrenici,  i.  571. 

communicating,  of  brain,  anterior,  i.  555. 
posterior,  i.  555. 
of  palm,  i.  586. 
coronary,  of  heart,  left,  i.  533. 
right,  i.  533. 
of  lips,  lower,  i.  543. 

upper,  i.  544. 
of  stomach,  i.  596. 
of  corpus  bulbosum,  i.  615. 

cavernosum,  i.  615. 
cremasteric,  i.  620. 
cystic,  i.  59k 
deferent,  ii.  553. 
dental  inferior,  i.  549. 

superior,  i.  549. 
digital,  of  foot,  633. 


Artery,  digital  of  hand,  i.  587. 

dorsal,  of  carpus,  radial,  i.  590. 
ulnar,  i.  586. 
of  foot,  i.  635. 
of  fore-finger,  i.  590. 
of  thumb,  i.  590. 
of  tongue,  i.  541. 
of  penis,  i.  615. 
of  great  toe,  i.  636. 
of  scapula,  i.  576. 
emulgent,  i.  602. 
epigastric,  i.  619,  ii.  582. 
superficial,  i.  623. 
superior,  i.  572. 
ethmoidal,  i.  554. 
facial,  i.  542. 
femoral,  i.  621,  625. 

deep,  i.  623. 
frontal,  i.  555. 
gastric,  i.  598., 
gastro-duodenal,  i.  597. 
epiploic,  left,  i.  599. 
right,  i.  597. 
gluttfial,  i.  616. 

heemorrhoidal,  external,  i.  615. 
middle,  i.  610. 
superior,  i.  601. 
helicine,  ii.  532. 
hepatic,  (d),  i.  597,  ii.  482,  478. 
humeral,  i.  578. 
hyoid  (lingual),  i.  542. 

(thyroid),  i.  540. 
hypogastric,  i.  608. 
iliac,  common,  i.  606. 
external,  i.  617. 
internal,  i.  608. 
of  foetus,  i.  609. 
ileo-colic,  i.  600. 
ilio-lumbar,  i.  617. 
infra-orbital,  i.  549. 
infra-spinous,  i.  569. 
innominate,  i.  534. 
intercostal,  (aortic,)  i.  594. 
anterior,  i.  571,  594. 
superior,  i.  572,  594. 
interlobular,  of  liver,  ii.  482. 
interosseous,  ulnar,  i.  585. 
anterior,  i.  585. 
posterior,  i.  585. 
of  foot,  i.  636. 
hand,  i.  590. 
intestini  tenuis,  i.  600. 
ischiadic,  i.  616. 
labial,  inferior,  i.  543. 
lachrymal,  i.  554. 
laryngeal,  i.  540. 
lingual,  i.  541. 
lumbar,  i.  604.  ^ 

malleolar,  external,  i.  635. 

internal,  i.  635. 
mammary,  external,  i.  576. 

internal,  i.  570. 
masseteric,  i.  549. 
maxillary,  external,  i.  542. 
inferior,  i.  549. 
internal,  i.  547. 
superior,  i.  549. 
mediastinal,  i.  571,  594. 
meningeal,  anterior,  i.  553. 
middle  or  great,  i.  548. 
posterior,  i.  565. 
small,  i.  549. 

mesenteric,  inferior,  i.  600. 


INDEX. 


611 


Artery,  mesenteric,  superior,  i.  599. 
metatarsal,  i.  636. 
middle  sacral,  i.  605. 
musculo-phrenic,  i.  571. 
mylo-hyoid,  i.  549. 
nasal,  i.  550. 

lateral,  i.  544. 
of  septum,  i.  550. 
nutrient  of  femur,  i.  622. 
fibula,  i.  631. 
humerus,  i.  581. 
radius,  i.  587. 
tibia,  i.  630. 
ulna,  i.  583. 
obturator,  i.  611. 
occipital,  i.  544. 
cesophstgeal,  i.  594. 
ophthalmic,  i.  553. 
ovarian,  i.  603. 
palatine,  ascending,  i.  543. 

superior  or  descending,  i.  550. 
palmar  arch,  superficial,  i.  586. 

deep,  i.  592. 
palpebral,  i.  554. 
pancreatic,  i.  598. 
pancreatic,  great,  i.  598. 
pancreatico-duodenal,  i.  597. 

inferior,  i.  599. 
perforating,  of  foot,  i.  633. 
hand,  i.  592. 
thigh,  i.  625. 
thorax,  i.  571. 
pericardiac,  i.  593. 
perinaeal,  superficial,  i.  615. 

transverse,  i.  615. 
peroneal,  i.  631. 
anterior,  i.  631. 
posterior,  i.  631. 
pharyngeal,  ascending,  i.  551. 
phrenic,  i.  603. 

superior,  i.  603. 
plantar,  external,  i.  632. 

internal,  i.  632. 
popliteal,  i.  627. 
princeps  cervicalis,  i.  545. 

pollicis,  i.  591. 
profunda,  of  neck,  i.  572. 
of  arm,  inferior,  i.  582. 

superior,  i.  581. 
of  penis,  i.  615. 
of  thigh,  i.  623. 
pterygoid,  i.  549. 
pterygo-palatine,  i.  550. 
pudic,  i.  613. 

accessory,  i.  614. 
in  female,  i.  615. 
external,  i.  623. 
pulmonary,  ii.  114. 
pyloric,  i.  597. 
radial,  i.  587. 

of  index  finger,  i.  591. 
ranine,  i.  542. 

recurrent  interosseous  posterior,  i.  585. 
radial,  i.  592. 
tibial,  i.  635. 
ulnar,  anterior,  i.  585. 
posterior,  i.  585. 
renal,  i.  602. 
sacral,  middle,  i.  605. 

lateral,  i.  617. 
scapular,  posterior,  i.  569. 
sciatic,  i.  616. 
sigmoid,  i.  601. 


Artery,  spermatic,  i.  602,  ii.  552. 
spheno-palatine,  i.  144. 
spinal,  anterior,  i.  565. 
in  neck,  i.  565. 
in  thorax,  i.  595. 
in  loins,  i.  604. 
median,  i.  566. 
posterior,  i.  565. 
splenic,  i.  598. 
sterno-mastoid,  i.  546. 
stylo-mastoid,  i.  546. 
subclavian,  i.  556. 
sublingual,  i.  542. 
submental,  i.  543. 
subscapular,  i.  568. 
superficial  circumflex  iliac,  i.  623. 
perinaeal,  i.  615. 
palmar  arch,  i.  586. 
superficialis  volae,  i.  590. 
supra-acromial,  i.  569. 
orbital,  i.  554. 
renal,  i.  601. 
scapular,  i.  568. 
spinous,  i.  568. 
sural,  i.  629. 
tarsal,  i.  635. 
temporal,  i.  546. 
anterior,  i.  547. 
deep,  i.  549. 
middle,  i.  547. 
posterior,  i.  547. 
thoracic  acromial,  i.  575. 
alar,  i.  576. 
long,  i.  576. 
superior,  i.  575. 
thymic,  i.  571, 

thyroid,  inferior,  (axis,)  i.  567. 
lowest,  i.  568. 
superior,  i.  540. 
tibial,  anterior,  i.  634. 

posterior,  i.  630.  » 

tonsillar,  i.  543. 
transverse,  of  face,  i.  547. 

neck,  i.  569.  , 

perinEeum,  i.  615. 
scapula,  i.  568. 
tympanic,  i.  548. 
ulnar,  i.  592. 
umbilical,  i.  609,  ii.  492. 
uterine,  i.  611. 
vaginal,  i.  611. 

of  liver,  ii.  428. 
of  vas  deferens,  i.  611,  ii.  553. 
vasa  aberrantia,  of  arm,  i.  580. 

brevia,  i.  598. 
vertebral,  i.  563. 
vesical,  inferior,  i.  610. 

superior,  i.  610. 
vesico-prostatic,  i.  610. 
vestibular,  ii.  393. 
vidian,  i.  550. 

Arthrodia,  i.  249. 

Articular  cartilage,  i.  239. 

Articulations,  atlo-axoid,  i.  252. 
acromio-clavicular,  i.  264. 
astragalo-calcaneal,  i.  286. 

scaphoid,  i.  287. 
of  axis  and  atlas,  i.  256. 
calcaneo-cuboid,  i.  286. 

scaphoid,  i.  287. 
carpal,  i.  271. 
carpo-metacarpal,  i.  272. 
costal,  i.  260. 


(512 


INDEX. 


Articulations,  costo-clavicular,  i.  264. 
cranio-vertebral,  i.  257. 
femoro-tibial,  i.  279. 
foot,  i.  285. 
by  gomphosis,  ii.  406. 
hand,  i.  271. 

humero-cubital,  i.  266. 
immovable,  i.  247. 
in  general,  i.  247. 
of  larynx,  ii.  129. 
lower  limb,  i.  278. 
mixed,  i.  248. 
movable,  i.  248. 
of  pelvis,  i.  274. 
peroneo-tibial,  i.  283. 
pubic,  i.  276. 

radio-cubital,  upper,  middle,  and  lower, 
i.  268,  269. 
carpal,  i.  270. 
of  ribs,  i.  260. 
sacro-iliac,  i.  275. 
sacro-vertebral,  i.  274. 
scapulo-humeral,  i.  265. 
sterno-clavicular,  i.  263. 
tarsal,  i.  286,  287. 
tarso-metatarsal,  i.  289. 
temporo-maxillary,  i.  259. 
of  tympanic  bones,  ii.  383. 
upper  limb,  i.  263.  • 

of  vertebral  column,  i.  252,  256. 

-\rytenoid  cartilages,  ii.  126. 

Aspera  arteria,  ii.  105. 

Assimilation,  i.  49. 

Atlas,  i.  111. 

.\trabiliary  capsules,  ii.  514. 

Atrium  cordis,  left,  i.  478. 
right,  i.  473. 

Auditory  canal,  external,  ii.  376. 

meatus,  external  and  internal,  ii.  387. 

Auricle  of  ear,  ii.  373. 

muscles  of,  ii.  375,  i.  334. 

Auricles  of  heart,  see  Heart. 

Auriculae,  of  heart,  i.  478. 

Auricular  appendices,  i.  478. 

Auriculo-ventricular  orifices,  i.  475,  479. 
size  of,  i.  487. 
rings,  i.  481. 
valves,  i 476,  480. 

Axilla,  i.  573. 

Axis,  i.  112. 

cerebro-spinal,  ii.  146,  155,  185. 
cceliac,  i.  596. 
thyroid,  i.  567. 
of  nerve  fibre,  ii.  151. 

Basement  membrane,  mucous,  ii.  80. 
serous,  ii.  76. 
of  skin,  ii.  86. 

Basilar  bone,  i.  1 15. 

Basis  of  cerebral  peduncle,  ii.  207. 

Bicuspid  teeth,  ii.  408. 

Bile,  ii.  488. 

Bile-duct,  common,  ii.  488. 
ducts,  in  general,  ii.  488. 

Bladder,  urinary,  ii.  517,  525. 
base  of,  ii.  518,  520. 

in  female,  ii.  520. 
coats  of,  cellular,  ii.  522. 
mucous,  ii.  522. 
muscular,  ii.  522. 
serous,  ii.  522. 
detrusor,  muscle  of,  ii.  523. 
development  of,  it.  569. 


Bladder,  female,  peculiarities  of,  ii.  520,  522. 
fundus  of,  inferior,  ii.  518,  520. 

superior,  ii.  518,  519. 
interior  of,  ii.  521. 
ligaments  of,  false,  ii.  519,  521. 

true,  ii.  519,  521. 
neck  or  cervix,  ii.  519,  521,  602. 
sacculated  and  fasciculated,  ii.  523. 
sphincter  muscle  of,  ii.  523. 
structure  of,  ii.  522. 
trigone  of,  ii.  522. 
uvula  of,  ii.  522. 
vessels  and  nerves  of,  ii.  524. 

Blastema,  ii.  91,  168. 

Blood,  i.  495. 

arterial  and  venous,  i.  507. 
chemical  composition  of,  i.  502. 
coagulation  of,  i.  500. 
colouring  principles  of,  i.  506. 
corpuscles,  pale,  i.  499. 

red,  i.  495. 
course  of,  i.  510. 
physical  properties  of,  i.  495. 
portal,  i.  508. 

table  of  composition  of,  i.  507. 

Blood-vessels,  general  anatomy  of,  i.  510. 
arterial,  see  arteries,  i.  512. 
capillary,  see  capillaries,  ii.  87. 
development  of,  i.  524. 
venous,  see  veins,  ii.  5. 

Bone,  general  anatomy  of,  i.  72. 
canaliculi  of,  i.  78. 
canals  of,  i.  75. 
cavities  of,  i.  73. 
chemical  composition,  i.  74. 
classes  of,  i.  72 
compact  or  cancellated,  i.  75. 
diploe  of,  i.  75. 
eminences  of,  i.  72. 
formation  and  growth  of,  i.  83. 
lacunte  or  corpuscles,  i.  77. 
lamellae  of,  i.  79. 
madder,  influence  of,  on,  i.  93. 
medulla  of,  i.  80. 
processes  of,  i.  72. 
structure,  i.  74. 
vessels  of,  i.  81. 

Bones,  descriptive  anatomy  of,  i.  95. 
astragalus,  i.  219. 
atlas,  i.  101,  111. 
axis,  i.  102,  112. 
calcaneum,  or  os  calcis,  i.  218. 
carpal,  i.  190. 
clavicle,  i.  180. 
coccy.x,  i.  106,  113. 
coronal,  i.  120.  ‘ 

costal,  i.  172. 
cuboid,  i.  219. 

cuneiform,  of  carpus,  i.  191. 

tarsus,  three  in  number,  i.  220. 
dentate,  i.  102,  112. 
ethmoid,  i.  134. 
femur,  i.  208. 
fibula,  i.  216. 
frontal,  i.  120. 
humerus,  i.  181. 
hyoid,  i.  151. 
ilium,  i.  198. 
incus,  ii.  381. 
innominate,  i.  198. 
ischium,  i.  201. 
lachrymal,  i.  145. 
lenticular,  ii.  382. 


INDEX. 


613 


Bones,  lingual,  i.  151. 
magnum,  i.  192. 
malar,  i.  144. 
malleus,  ii.  381. 
maxillary,  superior,  i.  139. 

inferior,  i.  148. 
metacarpal,  i.  193,  197. 
metatarsal,  i.  221. 
nasal,  i.  144. 

navicular,  of  carpus,  i.  190. 

tarsus,  i.  220. 
number  of,  i.  95. 
occipital,  i.  115. 
of  hand,  i.  190. 
wrist,  i.  199. 
fingers,  i.  194,  196. 
heart,  i.  482. 
limb,  upper,  i.  175. 

lower,  i.  183,  208. 
foot,  i.  217. 
ankle,  i.  218,  224. 
toes,  i.  222. 
skull,  i.  115. 
thorax,  i.  169. 
ear,  ii.  381. 
orbicular,  ii.  381. 
palate,  i.  145. 
parietal,  i.  119. 
patella,  i.  212. 
pelvic,  i.  205. 

phalangal,  of  hand,  i.  194,  196. 

foot,  i.  224,  218. 
pisiform,  i.  191. 
pubic,  i.  200. 
radius,  i.  185. 
ribs,  i.  172. 

true  and  false,  i.  172. 
peculiarities  of  some,  i.  174. 
sacrum,  i.  103,  113. 
scaphoid  of  carpus,  i.  190. 

tarsus,  i.  220. 
scapula,  i.  175. 
semilunar,  i.  191. 

sesamoid,  in  hand,  and  in  foot,  i.  223. 

spongy,  i.  130,  137,  148,  162. 

sphenoid,  i.  1^. 

stapes,  ii.  381. 

sternum,  i.  169. 

tarsal,  i.  217. 

temporal,  i.  123. 

tibia,  i.  213. 

trapezium,  i.  192. 

trapezoid,  i.  192. 

triquetral,  i.  117,  138. 

turbinate,  superior,  i.  137. 

inferior,  i.  148. 
tympanic,  i.  127. 
ulna,  i.  188. 
unciform,  i.  192. 
ungual,  i.  145. 
vertebra,  dentata,  i.  102. 

prominens,  i.  102. 
vertebrae,  i.  96. 

cervical,  i.  98,  111. 
dorsal,  i.  99,  112. 
lumbar,  i.  100. 
cranial,  i.  164. 

Wormkna.  i.  117,  138. 
vomer,  i.  147. 

Brain,  ii.  202. 

weight  of,  ii.  203, 
and  spinal  cord,  ii.  190. 
development  of,  ii.  253. 


Brain,  internal  structure,  ii.  228. 
membranes  of,  ii.  247. 
vessels  of,  ii.  253. 

Bronchi,  right  and  left,  ii.  106, 
structure  of,  ii.  108. 

Bronchia,  ii.  116. 

structure  of,  ii.  116. 
subdivisions  of,  ii.  117. 

Bronchial  tubes,  see  bronchia. 

vessels,  ii.  120.  (See  arteries  and  veins.) 

Bulb  of  urethra,  ii.  536. 

Bulbs  of  corpora  cavernosa,  ii.  529. 
fornix,  ii.  208. 
vestibule,  ii.  557. 

Bulbous  portion  of  urethra,  ii.  536. 

Bulbus  arteriosus,  ii.  534. 

Bursae  mucosae,  or  synovial,  i.  246. 

Caecum,  ii.  464.  See  intestine,  large. 

Calamus  scriptorius,  ii.  200. 

Calcar  avis,  ii.  217. 

Calices  of  kidney,  ii.  509,  516. 

Canal,  alimentary,  ii.  404. 

abdominal  portion,  ii.  472. 
auditory,  external,  ii.  376. 
of  Bichat,  ii.  222. 
carotid,  i.  125. 
centra!  of  modiolus,  ii.  390. 
for  chorda  tympani  nerve,  i.  125,  ii.  378. 
of  cochlea,  ii.  389. 
crural,  ii.  595. 
dental,  i.  149. 
of  epididymis,  ii.  519. 
femoral,  ii.  595. 
of  Fontana,  ii.  365. 
godronne,  ii.  371. 
of  Huguier,  ii.  378. 
hyaloid,  ii.  371. 
infra-orbital,  i.  140. 
inguinal,  ii.  583. 
lacrymal,  i.  134,  145,  160. 
nasal,  i.  161. 
of  Nuck,  ii.  544,  586. 
palatine,  anterior,  i.  140. 

posterior,  i.  140,  146. 
of  Petit,  ii.  372. 
pterygoid,  i.  132. 
pterygo-palatine,  i.  130,  147. 
spiral,  of  cochlea,  ii.  389. 

modiolus,  ii.  389. 
tympanic,  ii.  379. 
vertebral,  i.  108. 
vidian,  i,  132. 
of  Wirsung,  ii.  495. 

Canaliculi  of  bone,  i.  78. 

Canals  of  Havers,  (bone,)  i.  75. 
lachrymal,  ii.  360. 
semicircular,  of  ear,  ii.  388. 

Canine  teeth,  ii.  407. 

Cancelli  of  bone,  i.  75. 

Canthi  of  eyelids,  ii.  358. 

Capillaries,  general  anatomy  of,  i.  520. 
contractility  of,  i.  521. 
development  of,  i.  524. 
network  of,  i.  520. 
peculiarities  of,  i.  521. 
structure  of,  i.  522. 
vital  properties  of,  i.  524. 
of  particular  organs,  see  those  organs. 

Capitula  laryngis,  Santorini,  ii.  127. 

Capsule  of  lens,  ii.  372. 

Glisson,  ii.  479. 

Capsules,  supra-renal,  ii.  514. 


VOL.  II. 


52 


614 


INDEX. 


Capsules,  development  of,  ii.  568. 
synovial,  i.  245. 

Caput  caecum  coli,  ii.  464. 
gallinaginis,  ii.  535. 

Carpus,  i.  190. 

articulations  of,  i.  271. 

Cartilage,  general  anatomy  of,  i.  237. 
articular,  i.  239. 
costal,  i.  172. 

of  epiglottis,  i.  241,  ii.  127. 
formation  of,  i.  54. 
fibro-,  i.  243. 

interarticular,  i.  243. 
temporary,  i.  238. 
varieties  of,  i.  238. 
yellow,  i.  241. 
cricoid,  ii.  125. 
cuneiform,  ii.  127. 
of  ear,  ii.  373. 
ensiform,  i.  170. 

interarticular  fibro-carpal,  i.  271. 
sacro-coccygean,  i.  274. 
intervertebral,  i.  253. 
pubic,  i.  277. 
fibro-,  lower  jaw,  i.  260. 
slerno-clavicular,  i.  263. 
acromio-clavicular,  i.  264. 
radio-ulnar,  i.  269. 
of  knee,  i.  282. 
thyroid,  ii.  124. 
xiphoid,  i.  170. 

Cartilages,  arytenoid,  ii.  126. 
of  bronchi,  ii.  108. 
bronchia,  ii.  116. 
larynx,  ii.  124. 

ossification  of,  ii.  140. 
structure  of,  ii.  128. 
nose,  ii.  397. 

semilunar  of  knee,  i.  282. 
sesamoid,  of  nose,  ii.  398. 
tarsal  of  eyelids,  ii.  359. 
trachea,  ii.  106. 

Santorini,  ii.  127. 

Wrisberg,  ii.  127. 

Cartilago  triticea,  ii.  128. 

Caruncula  lachrymalis,  ii.  360. 

Carunculae  myrtiformes,  ii.  556. 

Casein,  i.  45,  505. 

Cauda  equina,  ii.  254,  296. 

Cavernous  plexus,  ii.  344. 
sinus,  ii.  262. 

nerves  in,  ii.  261. 

Cavities  of  bones,  i.  73. 

of  reserve  (teeth),  ii.  424. 
posterior,  ii.  426. 

Cavity,  glenoid,  i.  178. 

Cell-gerrn,  i.  55. 

nature  of,  i.  56. 

Cells,  alterations,  substance  and  contents  of,  i. 

64. 

complex,  i.  60. 

division  of,  into  fibres,  i.  65. 

epidermoid,  ii.  84. 

formation  of,  i.  57. 

hepatic,  ii.  64,  485. 

multiplication  by  sprouting,  i.  62. 

of  nervous  substance,  see  Nerve  Cells. 

origin  and  multiplication  of,  i.  56. 

origin  of,  from  nucleus,  i.  57. 

origin  of,  without  nuclei,  i.  62. 

pigment,  i.  64,  ii.  69,  85. 

reduplication  of,  i.  61. 

secreting,  ii.  98. 


Cells,  structure  of,  i.  55. 
transformation  of,  i.  63. 
vegetable,  i.  52. 
of  bones,  see  Sinuses. 

Cellular  tissue,  i.  227. 

varieties  of.  i.  227. 
filaments  of,  i.  228. 
yellow  fibres  of,  i.  229. 

Cement  of  teeth,  ii.  415. 

development  of,  ii.  423. 

Centres  of  ossification,  i.  23. 

Centrum  geminum  semicirculare,  ii.  220. 
ovale,  ii.  211. 

minus,  ii.  211. 

Cerebellum,  ii.  196,  224. 
crura  of,  ii.  224. 
fissures  of,  ii.  225. 
general  anatomy  of,  ii.  224. 
internal  structure  of,  ii.  235. 
lobes  of,  ii.  226. 
peduncles  of,  ii.  224,  256.' 
sections  of,  ii.  228. 
ventricle  of,  ii.  226. 
weight  of,  ii.  189. 

Cerebral  convolutions,  ii.  203,  204. 
classification  of,  ii.  206. 
ventricles,  ii.  213. 

Cerebric  acid,  i.  48. 

Cerebro-spinal  axis  or  centre,  ii.  155. 

internal  structure  of,  ii.  228. 
development  of,  ii.  253. 
general  anatomy  of,  ii.  155. 
fluid,  ii.  252. 

Cerebrum,  ii.  195,  202. 
base,  ii.  207. 
convolutions  of,  ii.  203. 
general  anatomy  of,  ii.  157. 
crura  of,  ii.  210. 
fibres,  ii.  239. 

ascending  or  peduncular,  ii.  236. 
transverse  or  commissural,  ii.  236. 
longitudinal  or  collateral,  ii.  236. 
Foville’s  views,  ii.  241. 
fissure,  transverse,  ii.  218. 

longitudinal,  ii.  202. 
hemispheres,  ii.  202. 
internal  parts  of,  ii.  210. 
internal  structure  of,  ii.  236. 
lobes,  ii.  203. 
peduncles  of,  ii.  210. 
sections  of,  ii.  210. 
under  surface,  ii.  202. 
upper  surface,  ii.  203. 
weight  of,  ii.  189. 

Cerumen  and  its  glands,  ii.  377. 

Cervix  uteri,  ii.  560. 
vesiccB,  ii.  521. 

Chambers  of  eye,  ii.  370. 

Cheeks,  li.  405. 

Chemical  nature  of  adipose  tissue,  i.  47,  ii. 
bile,  ii.  488. 
blood,  i.  502. 
bone,  i.  74. 
cartilage,  i.  242. 
cellular  tissue,  i.  230. 
cuticle,  ii.  85. 
cutis  or  corium,  ii.  88. 
elastic  tissue,  i.  236. 
fibro-cartilage,  i.  244. 
fibrous  tissue,  i.  234. 
hairs,  ii.  292. 
mucus,  ii.  83. 
muscular  tissue,  i.  313. 


INDEX. 


615 


Chemical  nature  of  nervous  substance,  ii.  148.  Contractility  of  arteries,  i.  516. 


pigment,  it.  79. 
textures,  i.  42. 
urine,  ii.  514. 

Chiasma  or  optic  commissure,  ii.  244. 

Chondrin,  i.  46. 

Chordae  tendineae  of  right  venticle,  i.  476. 
left  ventricle,  i.  480. 
vocales,  i.  482. 

Willisii,  ii.  22. 

Choroid  plexuses,  ii.  214. 

of  fourth  ventricle,  ii.  228. 
third  ventricle,  ii.  218. 
tunic  of  eye,  ii.  364. 

Chyle,  ii.  35. 

corpuscles,  ii.  35. 
plasma  of,  ii.  36. 
globules,  formation  of,  ii.  37. 

Chyliferous  vessels,  ii.  45. 

Ciliary  arteries,  see  Arteries, 
body,  ii.  365. 
ganglion,  ii.  267.  ' 

ligament,  ii.  365. 
nerves,  long,  ii.  266. 

short,  ii.  268. 
processes,  ii.  365,  371. 
zone,  ii.  366,  371. 

Cilia,  or  eyelashes,  ii.  360. 
vibratile,  ii.  65. 

Ciliary  motion,  ii.  65. 

Ciliated  epithelium,  ii.  64. 

Circle  of  Willis,  i.  555. 

Circulation  of  blood,  i.  510. 

Circulus  articuli  vasculosus,  i.  242. 
iridis,  ii.  367. 
tonsillaris,  i.  543. 
venosus  of  nipple,  ii.  576. 

Claustrum,  ii.  238. 

Clitoris,  ii.  554. 

development  of,  ii.  573. 
erector  muscles  of,  ii.  555. 

Coagulation  of  blood,  i.  500. 

Coccyx,  i.  106,  113. 

Cochlea,  ii.  388. 

aqueduct  of,  i.  126,  ii.  390. 
membranous  structure  of,  ii.  392. 
nerves  of,  ii.  395,  396. 
scalae  of,  ii.  390. 
vessels  of,  ii.  393. 

Colliculus  bulbi  urethrae,  ii.  533. 

(retina),  ii.  369. 

Colon.  See  Intestine,  large,  ii.  466. 

Columella  cochlete,  ii.  389. 

Columnae  carneae,  left  ventricle,  i.  479. 
right  ventricle,  i.  475. 
rugarum,  ii.  558. 

Commissure  optic,  ii.  209,  245. 

of  cerebrum,  anterior,  ii.  221,  239. 
middle  or  soft,  ii.  221. 
posterior,  ii.  222,  239. 

Commissures  of  spinal  cord,  ii.  139. 

Conarium,  ii.  222. 

Concha,  external  ear,  ii.  374. 

Condyles  of  bones,  see  the  Bones. 

Conglobate  glands,  ii.  42. 

Conglomerate  glands,  ii.  102. 

Coni  gemini  (retina),  ii.  369. 
vasculosi,  ii.  549. 

Conjoined  tendons,  i.  417,  ii.  581. 

Conjunctiva,  ii.  361. 

Contractility,  vital,  i.  516. 
muscular,  i.  325. 
non-muscular,  i.  50,  330. 


capillaries,  i.  521. 
skin,  ii.  95. 
veins,  i.  519. 

Conus  arteriosus,  i.  475. 

Convolutions,  cerebral,  ii.  203. 

classification  of,  ii.  206. 
j intestinal,  ii.  461. 

j Corium.  See  Skin,  ii.  85. 

! of  mucous  membrane,  ii.  79. 

Cornea  elastica.  ii.  363. 
j opaca,  ii.  363. 

I pellucida,  ii.  263. 

Cornicula  laryngis,  ii.  127. 

Cornu  Ammonis,  ii.  218. 

Cornua  of  ventricles,  ii.  213. 

Corona  glandis,  ii.  528. 
radiata,  ii.  235. 

Corpora,  albicantia,  ii.  208,  239. 

Arantii,  i.  478,  481. 
cavernosa  of  .penis,  ii.  529. 
structure  of,  ii.  530. 
helicine  arteries  of,  ii.  532. 
of  clitoris,  ii.  554. 
mammillaria,  ii.  208,  239. 
olivaria,  ii.  199. 
pyramidalia,  ii.  198. 
quadrigemina,  ii.  223,  256. 
restiformia,  ii.  199,  256. 
striata,  ii.  214,  220,  257. 

Wolffiana,  ii.  567. 

Corpus  callosum,  peduncles  of,  ii.  202. 
ventricles  of,  ii.  211. 
fibres  of,  ii.  239. 
callosum,  ii.  202,  211,  222. 
ciliare,  ii.  199,  365. 

dentatum  of  olivary  body,  ii.  199,  332. 
cerebelli,  ii.  228. 
fimbriatum,  ii.  217. 
geniculatuin  externum,  ii.  224. 

internum,  ii.  224. 

Highmorianum,  ii.  546. 
luteum,  ii.  565. 
i psalloides,  ii.  216. 

; spongiosum  urethrae,  ii.  533. 

I structure  of,  ii.  533. 

i vitreura,  ii.  371. 

Corpuscles  ofiblood,  formation  of,  i.  508- 
bone,  i.  77. 

chyle,  formation  of,  ii.  35. 

hepatic,  ii.  485. 

lymph,  formation  of,  ii.  38. 

Corpuscles,  Malpighian,  of  kidney,  ii.  509,  512. 
of  nervous  substance,  see  Nerve-cells, 
splenic,  ii.  499. 
of  suprarenal  bodies,  ii.  515. 
of  thymus,  ii.  144. 

! of  thyroid,  ii.  141. 

' Cortical  substance  of  kidney,  ii.  508. 

I Cotyloid  cavity  and  notch,  i.  202,  204. 
j ligament,  i.  278. 

Cowper’s  glands,  ii.  587. 
development  of  ii.  574. 

Cranial  nerves,  classification  of,ii.  259,  242, 246. 
roots  of,  ii.  242,  246. 
first  pair.  ii.  243,  260,  369. 
second  pair,  ii.  244,  260,  402. 
third  pair,  ii.  245,  261. 
fourth  pair,  ii.  245,  262. 
fifth  pair,  ii.  245,  263,  264,  277. 

its  three  divisions,  ii.  264,  277. 
sixth  pair,  ii.  246,  278. 
seventh  pair,  ii.  236,  278,  393. 


616  INDEX. 


Cranial  nerves,  seventh  pair,  its  two  portions, 
ii.  278. 

eighth,  first  part,  ii.  247,  283. 
second  part,  ii.  285,  567. 
third  part,  ii.  292. 
ninth  pair,  ii.  247,  292. 

Cranium.  (See  Skull.) 
size  of,  to  face,  i.  167. 

Crassamentum,  i.  504. 

Cremaster  muscle,  ii.  541. 
formation  of,  ii.  572. 

Cremasteric  fascia,  ii.  541. 

Crest  of  urethra,  ii.  535. 

Cribriform  fascia,  i.  308,  ii.  592. 
lamina  of  ethmoid  bone,  i.  135. 
sclerotic,  ii.  363. 
temporal  bone,  i.  126. 

Cricoid  cartilage,  ii.  125. 

Crista  gain,  i.  135. 
ilii,  i.  199. 
pubis,  i.  201. 
urethrae,  ii.  535. 
vestibuli,  ii.  387. 

Cruror,  i.  503. 

Crura  cerebri,  ii.  224,  236. 

Crura  cerebelli,  ii.  196,  232, 
of  clitoris,  ii.  554. 
penis,  ii.  524. 
fornix,  ii.  216. 
diaphragm,  i.  423. 

Crural  arch,  ii.  591. 

deep,  ii.  593. 
canal,  ii.  595. 
septum,  ii.  595. 

Crust  of  cerebral  peduncle,  ii.  237. 

Crusta  petrosa,  ii.  416. 
development,  ii.  422. 

Crypt,  ii.  100. 

multilocular,  ii.  101. 

Crypts,  of  Lieberkuehn,  ii.  457. 
large  intestine,  ii.  463. 

Crystalline,  ii.  372. 

Cul-de-sac,  of  pleura,  ii.  441. 
recto-uterine,  ii.  462. 
recto-vesical,  ii.  468,  520. 
of  stomach,  ii.  457. 

Cupola,  ii.  389. 

Cuspidate  teeth,  ii.  407. 

Cuticle,  ii.  59. 

Cutis,  vera,  ii.  84.  (See  Skin.) 

Cystic  duct,  ii.  490. 

Cystis  fellea,  ii.  488. 

Cytoblast,  i.  55. 

Cytoblastema,  i.  55. 

Dartos,  ii.  541. 

its  fibres,  i.  322. 

Decussation  of  pyramids,  ii.  198. 

Dens  sapientiae,  ii.  408. 

Dental  arches,  ii.  405. 

glands,  (Serres,)  ii.  408. 
grooves,  ii.  417. 
papillae,  ii.  417. 
periosteum,  ii.  406. 
pulps,  ii.  410. 
sacs,  permanent,  ii.  419. 

temporary,  ii.  423. 
tubuli,  ii.  411. 

Denticulate  ligaments,  ii.  252. 

Dentine,  ii.  411. 

development  of,  ii.  417. 
secondary,  ii.  417. 

Derma,  ii.  85.  (See  Skin.) 


Descent  of  testicle,  ii.  543,  573. 

Development  of  adipose  tissue,  li.  71. 
alimentary  canal,  ii.  472. 
anal  orifice,  ii.  473,  573. 
bladder,  ii.  573. 
blood  corpuscles,  i.  508. 
bone,  i.  83. 

brain  and  spinal  cord,  ii.  253,  354. 
cartilage,  i.  54. 
cellular  tissue,  i.  231. 
clitoris,  ii.  573. 

cremaster  muscle,  ii.  572.  o 
epithelium,  i.  67,  ii.  63. 

Fallopian  tubes,  ii.  571. 
fibro-cartilage,  i.  244. 
fibrous  tissue,  i.  235. 
generative  organs,  ii.  570. 

external,  ii.  573. 
gall-bladder,  ii.  491. 
great  vessels,  i.  488. 
gray  and  white  nervous  substance,  ii.  183. 
heart,  i.  488. 
hair,  ii.  92. 
hymen,  ii.  574. 

intestine,  large  and  small,  ii.  473. 

kidneys,  ii.  568. 

larynx,  ii.  139. 

liver,  ii.  491. 

lungs,  ii.  122. 

lymph  and  chyle,  ii.  36. 

membranes  of  encephalon,  ii.  258. 

mesentery,  ii.  472. 

muscular  tissue,  i.  323. 

neck  of  male  bladder,  ii.  569. 

nerves,  ii.  183. 

cesophagus,  ii.  472. 

ovaries,  ii.  571. 

pancreas,  ii.  496. 

penis,  ii.  573,  574. 

perinseum,  ii.  573. 

pigment  cells,  ii.  70. 

prostate,  ii.  573. 

prostatic  part  of  urethra,  ii.  573. 

salivary  glands,  ii.  440. 

scrotum,  ii.  572. 

spleen,  ii.  500. 

stomach,  ii.  472. 

suprarenal  capsule,  ii.  568. 

teeth,  ii.  417. 

enamel,  ii.  422. 
dentine,  ii.  420. 
cement,  ii.  423. 
textures,  animal,  i.  51. 

vegetable,  i.  51. 
testes,  ii.  571. 
thymus,  ii.  145. 
thyroid  body,  ii.  142. 
trachea,  ii.  122. 
tunica  vaginalis,  ii.  572. 
ureters,  ii.  568. 
urethra  of  female,  ii.  573. 
urinary  organs,  ii.  567. 
uterus,  ii.  573. 
vagina,  ii.  573. 
vasa  deferentia,  ii.  571. 
vulva,  ii.  573. 

Diaphragm,  i.  422. 

its  foramina,  i.  423. 

Diaphysis,  i.  72. 

Diploe,  i.  75. 

Diarthrosis,  i.  248. 

Dissection  of  muscles  of  abdominal  parietes, 
i.  414,  ii.  581. 


INDEX. 


617 


Dissection  of  arm,  i.  334. 
auricular  region,  i.  334. 
back,  i.  367,  371,  374,  379. 
face,  i.  334. 
foot,  i.  456,  458. 
forearm,  i.  396. 
gluteal  region,  i.  429. 
hand,  i.  408. 
head,  i.  331. 
leg,  i.  429,  432. 
lumbar  fascia,  i.  304. 
neck,  i.  349. 
orbit,  i.  346. 
palate,  i.  365. 
pharynx,  i.  361. 
soft  palate,  i.  365. 
temporo-maxillary  region,  i.  43. 
thigh,  anterior,  i.  435. 
internal,  i.  440. 
posterior,  i.  445. 

Dissector,  directions  to  the,  i.  331,  462. 

Duct,  aberrant,  of  liver,  ii.  485. 
of  Bartholine,  ii.  439. 
bile,  common,  ii.  479. 
biliary,  or  hepatic,  ii.  479,  483,  484. 

origins  of,  ii.  484. 
cystic,  ii.  490. 
ejaculatory,  ii.  552. 
nasal,  ii.  361. 
pancreatic,  ii.  495. 
parotid,  ii.  438. 

Stenonian,  ii.  438. 
thoracic,  ii.  44. 
right,  ii.  44. 

Duct,  Whartonian,  ii.  439. 

Ducts  of  glands,  in  general,  ii.  104. 

Bellini,  ii.  510. 
galactophorous,  ii.  575. 
of  kidney,  ii.  509. 

Ductus  ad  nasura,  ii.  361. 
arteriosus,  i.  490,  492. 

closure  of,  i.  494. 
communis  choledochus,  ii.  490. 
venosus,  ii.  478. 

closure  of,  i.  494. 
fossa  of,  ii.  478. 

Ductus  Riviniani,  ii.  439. 

Duodenum,  ii.  459,  see  Small  Intestine, 

Dura  mater,  ii.  248. 

Ear,  ii.  373. 

external,  ii.  373. 

cartilage  of,  ii.  375. 
ligaments  of,  ii.  375. 
muscles,  extrinsic,  i.  334. 
intrinsic,  ii.  375. 

internal, or  labyrinth,  ii.  386, (see Labyrinth.) 

nerves  of,  ii.  376. 
meatus  of,  external,  ii.  376. 
internal,  i.  126. 

middle,  or  tympanum,  ii.  377,  (see  Tym- 
panum.) 

ossicula  of,  ii.  381. 

Ejaculatory  ducts,  ii.  551. 

Elastic  fibres  of  cellular  tissue,  i.  229. 
tissue,  i.  235. 

Eminences  of  bones,  i.  72. 

Eminentia  collateralis,  ii.  217. 
papillaris  (tympanum),  ii.  380. 

Enamel-membrane,  ii.  422. 

Enamel,  of  teeth,  ii.  422. 

development  of,  ii.  422. 
pulp,  ii.  422. 


Enarthrosis,  i.  249. 

Encephalon,  blood-vessels  of,  ii.  254. 
development  of,  ii  254. 
internal  structure  of,  ii.  235,  236. 
gray  matter  of,  ii.  158,  241. 
membranes  of,  ii.  258. 
primary  divisions  of,  ii.  195. 
weight  of,  ii.  189. 

Endocardium,  i.  481. 

Endo-lymph,  ii.  392. 

Endosmosis,  i.  41. 

Endosteum,  i.  80. 

Epidermis,  ii.  59,  84. 

Epididymis,  ii.  545. 
canal  of,  ii.  5,  19. 
lobes  of,  ii.  5,  19. 

Epiglottis,  ii.  127. 

Epiphyses,  i.  72,  110. 

Epiploon,  great,  ii.  501. 
small,  ii.  502. 

Epithelium,  in  general,  ii.  59. 
of  air-cells,  ii.  117. 
arachnoid,  ii.  151. 
arteries,  i.  514. 
bladder,  ii.  525. 
bronchi,  ii.  109. 
bronchia,  ii.  116, 

capsules  of  Malpighian  bodies,  ii.  509, 
512. 

ciliated,  ii.  64. 
columnar,  ii.  62. 
of  conjunctiva,.!!.  62. 
cornea,  ii.  80. 
ducts  of  glands,  ii.  105. 

Eustachian  tube,  ii.  385. 

Fallopian  tube,  external,  ii.  566. 

internal,  ii.  566. 
gall  bladder,  ii.  263,  489. 
large  intestine,  ii.  464. 
larynx,  ii.  138. 
lymphatics,  ii.  39. 
mouth,  ii.  435. 

mucous  membranes,  ii.  39,  62. 
nasal  fossae,  ii.  400. 

sinuses,  ii.  400. 
nose,  ii.  400. 
oesophagus,  ii.  441. 
pericardium,  ii.  60. 
peritoneum,  ii.  60,  500. 
pharynx,  ii.  440. 
pleura,  ii.  60. 
prostatic  ducts,  ii.  52. 
scaly  or  squamous,  ii.  60. 
of  seminiferous  tubes,  ii.  547. 
serous  membranes,  ii.  60,  76. 
small  blood-vessels,  i.  515. 
small  intestine,  ii.  62,  455,  457. 
spheroidal,  ii.  63. 
of  stomach,  ii.  451. 
stratified,  ii.  61 . 

of  synovial  membranes,  i.  240,  244. 
tongue,  ii.  431. 
trachea,  ii.  108. 
transitional,  ii.  64. 
of  tubuli  uriniferi,  ii.  511. 

seminiferi,  ii.  548. 
tunica  vaginalis  testis,  ii.  544. 
tympanum,  ii.  385. 
ureters,  ii.  517. 
urethra,  ii.  525. 
uriniferous  tubes,  ii.  511. 
uterus,  ii.  562. 
vagina,  ii.  558. 


52* 


INDEX. 


618 


Epithelium,  vas  deferens,  ii.  551. 
veins,  i.  518. 
velum  palali,  ii.  441. 
ventricles  of  brain,  ii.  213. 
vesiculs  seniinales,  ii.  552. 
vulva,  ii.  556. 

Epicondyle,  i.  184. 

Epitrochlea,  i.  184. 

Erestile  tissue,  general  characters  of,  i.  524. 
of  penis,  ii.  530,  533. 
vulva,  ii.  5^. 

Ergot,  ii.  215,  217. 

Eustachian  tube,  i.  127,  ii.  380. 

Excretion,  ii.  98. 

Exosmosis,  i.  41. 

Extractive  matters,  i.  46,  505. 

Eye,  ii.  358. 

appendages  of,  ii.  358. 
ball  or  globe  of,  ii.  362. 
brows,  ii.  358. 
chambers  of,  ii.  370. 
coats,  ii.  362. 
humours  of,  ii.  370. 
aqueous,  ii.  370. 
crystalline,  ii.  372. 
vitreous,  ii.  370. 
lashes,  ii.  360. 
lens  of,  ii.  372. 
lids,  ii.  358. 

cartilages  of,  ii.  359. 
glands  of,  ii.  360. 

mucous  membrane,  conjunctival,  ii. 

361. 

membranes,  ii.  364. 

of  aqueous  humour,  ii.  363,  370. 
capsule  of  lens,  ii.  372. 
choroid,  ii.  364. 
cornea,  ii.  363. 
hyaloid,  ii.  370, 
iris,  ii.  368. 

Jacob’s,  ii.  367. 
pigment,  ii.  365. 
pupillary,  ii.  373. 
retina,  ii.  369. 

Ruysch’s,  ii.  364. 
sclerotic,  ii.  362. 
vitreous  humour,  ii.  370. 
muscles  of,  i.  346. 

nerve  of  (optic),  ii.  168,  244,  260,  368. 
pigment,  ii.  69,  364. 
teeth,  ii.  407. 

Face,  bones  of,  i.  139. 

Facial  angle,  i.  168. 

Falciform  process,  ii.  592. 

Fallopian  tubes,  ii.  565. 

development  of,  ii.  571. 
fimbriae  of,  ii.  566. 
orifices  of,  ii.  566. 

Falx  cerebri,  ii.  249. 

cerebelli,  ii.  225,  249. 

Fascia,  i.  232,  292. 

Fascia  abdominal,  i.  301,  302. 
of  biceps  of  arm,  i.  299. 
brachial,  i.  298. 
cervical,  deep,  i.  295. 

superficial,  i.  295. 
costo-coracoid,  i.  297. 
cremasteric,  ii.  531. 
cribriform,  i.  308,  ii.  592. 
dentata,  ii.  217. 
dorsal,  of  foot,  i.  311 . 
of  lore-arm,  i.  299. 


Fascia  of  hand,  i.  300. 

of  head  and  neck,  i.  294. 
iliac,  i.  303. 

infundibuliform,  ii.  542. 
intercolumnar,  ii.  541,  579. 
intercostal,  i.  298. 
inter-muscular,  i.  293. 
inter-muscular  of  arm,  i,  299. 
of  thigh,  i.  309. 
of  foot,  i.  312. 
lata,  i.  308. 

muscles  of,  i.  293. 
of  leg,  i.  310. 
of  upper  limb,  i.  298. 
of  lower  limb,  i.  307. 
hsmborum,  i.  304,  420. 
of  mammary  gland,  ii.  575, 
obturator,  i.  306. 
palmar,  i.  300. 
parotid,  i.  295. 
pelvic,  i.  305. 

perineal,  deep,  i.  304,  ii.  600. 

superficial,  i.  304,  ii.  509. 
plantar,  i.  311. 
prevertebral,  i.  297. 
propria,  femoral,  ii.  595. 

inguinal,  ii.  543. 
recto-vesical,  i.  306. 
spermatic,  ii.  541,  579. 
superficial,  i.  293. 
abdominal,  i.  302. 
perineal,  i.  304. 
of  groin,  i.  307,  ii.  578. 
temporal,  i.  295,  344. 
of  thorax,  i.  297. 
transversalis,  i.  302,  ii.  582,  594. 
vesical,  i.  307. 

Fasciculi  graciles,  ii.  200. 
teretes,  ii.  200,  227. 
of  muscle,  i.  314. 
of  nerve,  ii.  163. 

Fasciculus  cuneatus,  ii.-231. 
nnciformis,  ii.  203. 

Fasciolte  cineretB,  ii.  227. 

Fat,  ii.  71. 

cells,  ii.  72. 
uses  of,  ii.  73. 

Fatty  matters,  i.  47,  505. 

saponifiable,  i.  47. 
unsaponifiable,  i.  48. 

Fauces,  ii.  404,  434. 

Femoral  arch,  ii.  591. 
deep,  ii.  593. 
canal,  ii.  595. 
hernite,  see  Hernia, 
ring,  ii.  594. 
sheath,  ii.  592. 

Fenestra  ovalis,  ii.  379,  387. 
rotunda,  ii.  380. 

Fenestrated  membrane,  i.  514. 
of  hair  follicle,  ii.  91. 

Fibrae  arciformes,  ii.  201,  234. 
transverste,  ii.  234. 

Fibrin,  i.  44. 

Fibro-cartilages,  i.  243. 

Fibro-serous  membranes,  i.  75. 

Fibrous  tissue,  i.  232. 

Fibrous  cone,  ii.  238. 

Filamentous  tissue,  i.  227. 

Fillet,  ii.  237. 

Fillet  of  corpus  callosum,  ii.  240. 

Fimbriae  of  Fallopian  tube,  ii.  565. 

Fissure  of  cerebellum,  ii.  225. 


INDEX. 


619 


Fissure,  Glaserian,  i.  125,  158,  ii.  379. 
longitudinal  of  cerebrum,  ii.  202. 
pterygo-maxillary,  i.  158. 
sphenoidal,  i.  132. 
spheno-inaxillary,  i.  158. 

Sylvian,  ii.  203. 

transverse  of  cerebrum,  ii.  218. 
of  Santorini,  ii.  377. 

Flocculus,  ii.  226. 

Foetus,  circulation  in,  i.  492. 

peculiarities  of  heart  in,  i.  491. 
liver  in,  ii.  491. 
lungs  in,  ii.  122. 

Folds,  aryteno-epiglottidean,  ii.  129. 
recto-uterine,  ii.  562. 

vesical,  ii.  521. 
vesico-uterine,  ii.  562. 

Folia  cerebelli,  ii.  235. 

Follicle,  ii.  100. 
of  hair,  ii.  90. 

Follicles,  sebaceous,  ii.  93. 

Foramen,  carotid,  i.  125,  155. 
centrale  (retina),  ii.  369. 
caecum  of  frontal  bone,  i.  122,  135. 

tongue,  ii.  430. 
condyloid,  i.  116,  156. 
dental,  inferior,  i.  149. 
infra-orbital,  i.  140. 
intervertebral,  i.  98. 
lacerum,  anterius,  i.  126,  155. 

posterius,  i.  126,  155. 
magnum,  i.  116. 
mastoid,  i.  125. 
mental,  i.  149. 
of  Monro,  ii.  219. 
obturator,  i.  203. 
occipital,  i.  116. 
optic,  i.  131,  132. 
ovale  (bone),  i.  132. 

of  heart,  i.  490,  491,  494. 
vestige  of,  i.  474,  479. 
palatine  anterior,  i.  140,  155. 

posterior,  i.  155. 
parietal,  i.  119. 
rotundum,  i.  132. 

sacro- sciatic,  great  and  small,  i.  276. 
spheno-palatine,  i.  147,  ii.  401. 
spinosum,  i.  132. 
of  Steno,  i.  141. 
stylo-mastoid,  i.  126. 
supra-orbital,  i.  121. 
thyroideum,  i.  203. 
of  Winslow,  ii.  502,  505. 

Foramina,  Thebesii,  i.  475,  ii.  32. 
dental,  superior,  i.  140. 
of  diaphragm,  i.  425. 
malar,  i.  144. 

orbital,  anterior  and  posterior,  i,  137,  160. 

Foreskin,  ii.  528. 

Fornix,  ii.  216,  256. 
bulbs  of,  ii.  208. 
fibres  of,  ii.  239. 

Fossa  of  anti-helix,  ii.  374. 
canine,  i.  140. 
cystis  felleae,  ii.  478. 
digastric,  i.  125. 
of  ductus  venosus,  ii.  478. 
glenoid,  i.  125. 
of  helix,  ii.  374. 
iliac,  i.  199. 
ischio-rectal,  ii.  604. 
infra  and  supra-spinous,  i.  177. 
jugular,  i.  126. 


Fossa  of,  myrtiform,  i.  140. 
navicular,  i.  131. 
navicularis,  of  urethra,  ii.  535. 

vulva,  ii.  554. 
ovalis,  heart,  i.  474. 
pituitary,  i.  129. 
pterygoid,  i.  131. 
spheno-maxillary,  i.  158. 
subscapular,  i.  176. 
temporal,  i.  157. 
trochanteric,  i.  210. 
zygomatic,  i.  158. 

Fossae,  nasal,  i.  161,  ii.  399. 
of  peritoneum,  ii.  584. 
of  skull,  internal,  i.  158. 

Fourchette,  ii.  554. 

Fovea  hemi-elliptica,  ii.  387. 
hemispherica,  ii.  387. 

Freenulum  pudendi,  ii.  554. 

Fraenum  lingutE,  ii.  429. 
of  lips,  ii.  405. 
praeputii,  ii.  528. 

Fringes,  synovial,  i.  245. 

Funiculi  of  nerve,  ii.  163. 

Furcula  of  sternum,  i.  170. 

Furrow,  auriculo- ventricular,  i.  472. 
inter-ventricular,  i.  472. 

Furrowed  band,  ii.  226. 

Galactophorus  ducts,  ii.  574. 

Gall-bladder,  ii.  489. 

development  of,  ii.  491. 
varieties  of,  ii.  491. 

Ganglia,  general  anatomy  of,  ii.  161. 
of  auditory  nerve,  ii.  168. 
cardiac,  i.  485. 
cephalic,  ii.  340. 
hypogastric,  ii.  354. 
inferior  maxillary  nerve,  ii.  277. 
lumbar,  ii.  347. 
lymphatic,  ii.  41. 
mesaraic,  ii.  352. 
of  nervi  molles,  ii.  343. 
renal,  ii.  351. 
sacral,  ii.  348. 
solar,  ii.  350. 
semilunar,  ii.  350. 
of  spinal  nerves,  ii.  295. 

sympathetic  nerves,  ii.  339. 
thoracic,  ii.  346. 

Gangliated  cords,  sympathetic,  ii.  341 
cervical  part,  ii.  341. 
lumbar  part,  ii.  347. 
sacral  part,  ii.  348. 
thoracic  part,  ii.  345. 

Ganglion,  azygos,  ii.  347. 
cervical,  inferior,  ii.  345. 
middle,  ii.  344. 
superior,  ii.  341. 
diaphragmatic,  ii.  351. 
on  facial  nerve,  ii.  279. 
of  fifth  pair,  or  Gasserian,  ii.  264. 
glosso-pharyngeal,  ii.  283. 
impar,  ii.  347. 
jugular,  ii.  283. 
lenticular,  ii.  266. 

Meckel’s,  ii.  270. 
ophthalmic,  ii.  267. 
otic,  ii.  277. 
petrous,  ii.  284. 
pneumogastric,  ii.  287,  288. 
of  portio  dura.  ii.  279. 
of  Ribes,  ii.  343. 


620 


INDEX. 


Ganglion,  semilunar,  ii.  350. 
spheno-palatine,  ii.  270. 
subma.villavy,  ii.  278. 
supra-renal,  ii.  351. 
thyroid,  ii.  3-14. 

Ganglion  globules,  ii.  153. 

Ganglionic  corpuscles,  ii.  153. 

Gastro-pulmonary  mucous  membrane,  i.  78. 

Gelatin,  i.  46. 

Gelatinous  compounds,  i.  45. 
nerve-tibres,  ii.  152. 
nature  of,  ii.  176. 

Germinal  spot,  ii.  565. 
vesicle,  ii.  565. 

Gums,  ii.  405. 

Gimbernat’s  ligament,  ii.  591. 

Ginglymus,  i.  250. 

Glabella,  i.  121. 

Glands,  secreting.  General  Anatomy  of,  ii.  97. 
acini  of,  ii.  102. 
cellular  tissue  of,  ii.  103. 
compound,  ii.  101. 
conglomerate,  ii.  102. 
crypts,  ii.  100. 
ducts  of,  ii.  104. 
envelope  of,  ii.  104. 
forms  of,  ii.  100. 
lacunae,  ii.  100. 
lobules  of,  ii.  101. 
lymphatics  of,  ii.  41,  103. 
multilocular  crypts,  ii.  101. 
nerves  of,  ii.  103. 
parenchyma  of,  ii.  103. 
peculiar,  ii.  103. 
racemose,  ii.  101. 
reservoirs  of,  ii.  104. 
simple,  ii.  100. 
substance  of,  ii.  103. 
tubular  compound,  ii.  100. 

simple,  ii,  100. 
vesicles  of,  ii.  101. 
vesicular,  ii.  103. 

Gland,  or  Glands,  accessory  of  parotid,  ii.  437. 
anti-prostatic,  ii.  537. 
agminated,  ii.  103,  467. 
arytenoid,  ii.  139. 
of  Bartholine,  ii.  556. 

Brunner’s,  ii.  102,  459. 
buccal,  ii.  405. 
ceruminous,  ii.  101,  377. 

Cowper’s,  ii.  537. 
epiglottic,  ii.  139. 
gastric,  tubular,  ii.  451. 

follicular,  ii.  452. 
of  Havers,  i.  245. 
labial,  ii.  405. 
lachrymal,  ii.  360. 
of  large  intestine,  ii.  463. 
laryngeal,  ii.  139. 
lingual,  ii.  432. 
liver,  ii.  474.  See  Liver, 
mammary,  ii.  574. 

Meibomian,  ii.  359. 
molar,  ii.  405. 

of  mucous  membrane,  ii.  82. 
mucilaginous  of  Havers,  i.  245. 
oesophageal,  ii.  443. 
of  Pacchioni,  ii.  249. 
palatine,  ii.  436. 

pancreas,  ii.  493.  See  Pancreas, 
parotid,  ii.  437. 
of  Peyer,  ii.  457. 
pineal,  ii.  162,  222. 


Gland,  pituitary,  ii.  162,  209. 
pharyngeal,  ii.  441. 
of  prepuce,  ii.  529. 
prostate,  ii.  526. 

anterior,  ii.  537. 
salivary,  ii.  437. 
sebaceous,  ii.  93. 
of  skin,  ii.  93. 
of  small  intestine,  ii.  457. 
solitary,  ii.  103,  458. 
sublingual,  ii.  439. 
submaxillary,  ii.  438. 
sudoriferous,  ii.  94. 
thymus,  ii.  142. 
thyroid,  ii.  140. 
tracheal,  ii.  108. 
of  Tyson,  ii.  529. 
uterine,  ii.  562. 
of  vulva,  ii.  556. 

Glands,  Lymphatic,  General  Anatomy  of,  ii.  41. 
conglobate,  ii.  41. 

Descriptive  Anatomy,  ii.  46. 
axillary,  ii.  57. 
bronchial,  ii.  56. 
cervical,  ii.  58. 
inguinal,  ii.  50. 
lumbar,  ii.  54. 
mediastinal,  ii.  56. 
mesenteric,  ii.  45. 
oesophageal,  ii.  56. 
popliteal,  ii.  49. 
thoracic,  ii.  55. 

Glandula  socia  parotidis,  ii.  437. 

Glandulce  Pacchioni,  ii.  249. 

Gians  penis,  ii.  528. 
clitoridis,  ii.  554. 

Glenoid  cavity,  i.  249. 
fossa,  i.  125. 
ligament,  i.  266. 

Globulin,  i.  503. 

Globus  major  and  minor,  ii.  545. 

Glomeruli  of  kidney,  ii.  512. 

Glottis,  ii.  130. 
rima  of,  ii.  132. 

Glycerine,  i.  47. 

Gomphosis,  i.  248,  ii.  406. 

Graafian  vesicles,  ii.  565. 
development  of,  ii.  571. 

Granules,  elementary,  i.  58. 

Groin,  anatomy  of,  ii.  578. 

Growth,  ii.  69. 

Gubernaculum  testis,  ii.  572. 

Gullet,  ii.  442. 

Gyri  of  brain,  ii.  202. 
operti,  ii.  203. 

Gyrus  fornicatus,  ii.  204. 
fibres  of,  ii.  240. 

Hoematin,  i.  503. 

Heematosin,  i.  503. 

Hairs,  ii.  88. 

attachment  of,  ii.  91. 
chemical  nature  of,  ii.  92. 
development  of,  ii.  92. 
distribution  of,  ii.  92. 
follicles,  ii.  90. 
growth  of,  ii.  91. 
medulla,  ii.  90. 
parts  of,  ii.  89. 
reproduction  of,  ii.  92. 
roots  of,  ii.  90. 
stem  of,  ii.  89. 

vessels  and  nerves  of,  ii.  91,  92. 


INDEX. 


621 


Halitus  of  blood,  i.  500. 

Ham,  region  of  the,  i.  628. 

Hamulus  of  cochlea,  ii.  390. 
sphenoid,  i.  131. 

Harmonia,  i.  248. 

Haversian  canals,  i.  75. 
glands,  i.  245. 

Heart,  i.  470. 

apex  of,  i.  471. 
atrium  of,  right,  i.  473. 
left,  i.  478. 

auricles,  in  general,  i.  472. 
auricle  of,  left,  i.  478. 

capacity  of,  i.  487. 
development  of,  i.  488. 
fibres  of,  i.  483. 
walls  of,  i.  473. 
right,  i.  478. 

capacity  of,  i.  487. 
development  of,  i.  488. 
fibres  of,  i.  483. 
walls  of,  i.  473. 

auricula  or  auricular  appendix,  left,  i.  478. 

auricular  appendix,  right,  i.  473. 
bone  of,  i.  482. 
cavities  of,  i.  473,  475. 

size  of,  i.  487. 
cellular  tissue  of,  i.  481. 
chordae  tendineae  of,  left  ventricle,  i.  480. 
right,  i.  476. 

columnae  carnete  of,  left  ventricle,  i.  479. 

right,  i.  475. 
development  of,  i.  488. 
double,  i.  473. 

fibrous  rings  of,  arterial,  i.  481. 

auriculo-ventricular,  i.  481. 
fibrous  structures  of,  i.  481 . See  also  V alves. 
fetal,  i.  491. 

foramina  of,  see  Foramen  and  Foramina. 

fossa  ovalis  of,  i.  474. 

furrow,  auriculo-ventricular,  i,  472. 

inter-ventricular,  i.  472. 
muscular  fibres  of,  i.  482. 
auricular,  i.  483. 
ventricular,  i.  484. 

musculi  papillares  of,  left  ventricle,  i.  479. 
right  ventricle,  i.  476. 
pectinati  of  left  auricle,  i.  478. 
right  auricle,  i.  473. 
nerves  of,  i.  485. 
office  of,  ii.  510. 
orifices  of,  aortic,  i.  480. 

auriculo-ventricular,  left,  i.  479,  480. 

right,  i.  475,  476. 
pulmonary,  i.  479. 
size  of,  i.  487. 
septum,  i.  472. 

auricular,  i.  474. 
ventricular,  i.  475. 
serous  coat,  external,  i.  481. 

internal,  i.  481. 
sinus  venosus  of,  left,  i.  478. 

right,  i.  473. 
structure  of,  i.  481. 
sulci  of,  i.  472. 

valves  of,  Eustachian,  i.  475,  491,  493. 
mitral  or  bicuspid,  i.  480. 

Thebesian,  i.  475. 
valves  of,  tricuspid,  i.  476. 
valves,  auriculo-ventricular,  left,  i.  480. 
right,  i.  476. 

sigmoid  or  semilunar,  left,  i.  481. 
right,  i.  476,  477. 


Heart,  ventricles,  in  general,  i.  472. 
ventricle  of,  left,  i.  479. 

capacity  of,  i.  487. 
fibres  of,  i.  484. 
walls  of,  i.  479,  487. 
right,  i.  475. 

capacity  of,  i.  487. 
fibres  of,  i.  484. 
walls  of,  i.  487. 
vessels  of,  i.  485. 
vortex  of,  i.  484. 
weight  of,  i.  486. 

Hearts,  lymphatic,  ii.  43. 

Helicine  arteries,  ii.  532. 

Helicotrema,  ii.  390. 

Helix,  ii.  374. 

muscles  of,  ii.  375. 
process  of,  ii.  375. 

Hemispheres,  cerebellar,  ii.  225. 
cerebral,  ii.  202,  257. 

Herniae,  abdominal,  ii.  577. 

anatomy  of,  femoral,  ii.  591. 

inguinal,  ii.  584. 
congenital,  ii.  585. 
coverings  of,  femoral,  ii.  595. 
inguinal,  direct,  ii.  586. 
oblique,  ii.  585. 
direct  or  internal,  ii.  585. 

in  the  female,  ii.  590. 
femoral,  ii.  591. 

diagnosis,  ii.  596. 
fascia  propria  of,  ii.  596. 
infantile,  ii.  586. 

inguinal,  direct  and  oblique,  ii.  584. 

diagnosis  of,  ii.  589. 
oblique  or  external,  ii.  584. 

in  the  female,  ii.  586. 
operations  for,  inguinal,  ii.  590. 

femoral,  ii.  596. 
sac  of,  ii.  585. 
scrotal,  ii.  585. 

Hiatus  Fallopii,  i.  126. 

Hilus  of  kidney,  ii.  507. 
liver,  ii.  477. 
spleen,  ii.  496. 

Hippocampus  major,  ii.  215,  217. 
minor,  ii.  215,  217. 

Horseshoe-kidney,  ii.  508. 

Humours  of  eye,  ii.  370,  373. 

Hymen,  ii.  556. 

development  of,  ii.  574. 

Ileo-ceecal,  or  ileo-colic  valve,  ii.  465. 

Ileum,  ii.  461.  (See  Small  Intestine.) 

Ilio-pectineal  eminence,  i.  200. 
line,  i.  205. 

Incisor  teeth,  ii.  406. 

Incisura  intergracia,  ii.  374. 

Incus,  ii.  383. 

Infundibula  of  kidney,  ii.  509. 

Infundibulum  (brain),  ii.  209,  256. 
(cochlea),  ii.  389. 

(heart),  i.  475. 

Inguinal  canal,  ii.  583. 

fossas,  of  peritoneum,  ii.  583. 
hernia,  (see  Herniae.) 
pouches,  (peritoneal,)  ii.  583. 

Interarticular  cartilage,  i.  260. 

Intervertebral  substance,  i.  253. 

Intestine-,  large,  ii.  462. 

caecum,  ii.  464. 
coats  of,  ii.  462. 
colon,  ii.  466. 


6-22 


INDEX. 


Intestines,  development  of,  ii.  472. 
divisions  of,  ii.  462. 
follicles  of,  ii.  463. 
glands  of,  ii.  463. 
lymphatics  of,  ii.  467. 
mucous  membrane  of,  ii.  463. 
rectum,  ii.  467. 
structure  of,  ii.  462,  468. 
tubuli  of,  ii.  463. 
valve  of,  ii.  465. 
vessels  and  nerves  of,  ii.  467. 

Intestine,  small,  ii.  453. 

capillaries  of,  ii.  456. 
coats  of,  ii.  453,  454. 
convolutions  of,  ii.  461. 
crypts  of,  ii.  457. 
development  of,  ii.  472. 
divisions  of,  ii.  453. 
duodenum,  ii.  459. 
epithelium  of,  ii.  455. 
follicles  of,  ii.  457. 
glands  of,  ii.  457. 

agminated,  ii.  457. 

Brunner’s,  ii.  459. 
solitary,  ii.  458. 
tubular,  ii.  457. 
ileum,  ii.  461. 
jejunum,  fi.  461. 
lacteals  of,  ii.  456. 
mesentery  of,  ii.  454. 
mucous  membrane  of,  ii.  454. 
structure  of,  ii.  453. 
tubuli  of,  ii.  457. 
valves  of,  ii.  455. 

vessels  and  nerves,  ii.  456,  459,  461. 
villi  of,  ii.  455. 

Involuntary  muscles,  i.  321. 

Iris,  ii.  366. 

.nerves  of,  ii.  367. 

Irritability,  muscular,  i.  325. 

duration  after  death,  i.  326. 

Ischio-rectal  fossa,,  ii.  604. 

Island  of  Reil,  ii.  203, 

Isthmus  faucium,  ii.  436. 

Vieussenii,  i.  474. 

Iter  a tertio  ad  quartum  ventriculum,  ii.  222. 
ad  infundibulum,  ii.  222. 

Ivory  of  teeth,  ii.  410. 

Jacob’s  membrane,  ii.  369. 

Jejunum,  ii.  461.  (See  Small  Intestine.) 

Joint,  ankle,  i.  284, 
elbow,  i.  266. 
hip,  i.  278. 

movements  of,  i.  250. 
lower  jaw,  i.  259. 
knee,  i.  279. 
shoulder,  i.  265. 

movements  of,  i.  250. 
wrist,  i.  270. 

Joints,  in  general,  i.  247. 
movements  of,  i.  249. 
synovial  membranes  of,  i.  245. 

Kidneys,  ii.  506. 

adipose  capsule  of,  ii.  507. 

calices  of,  ii.  509,  516. 

capillaries  of,  ii.  512. 

coat  of,  fibrous,  ii.  508. 

corpuscles  of,  Malpighian,  ii.  509,  512. 

cortical  substance  of,  ii.  508,  509. 

development  of,  ii.  514. 

ducts  of,  ii.  509. 


Kidneys,  Bellini’s,  ii.  510. 
glomeruli  of,  ii.  512. 
hilus  or  fissure  of,  ii.  507. 
horseshoe,  ii.  507. 
infundibula  of,  ii.  509. 
lymphatics  of,  ii.  514. 
medullary  substance  of,  ii.  508,  509. 
nerves  of,  ii.  514. 
papillaa  of,  ii.  508. 
parenchyma  of,  ii.  514. 
pelvis  of,  ii.  509,  516. 
primitive  or  primordial,  ii.  567. 
pyramids  of,  Ferrein’s,  ii.  510. 

Malpighi’s,  ii.  508,  509. 
sinus  of,  ii.  508. 
structure  of,  ii,  507. 
tubuli  of,  convoluted,  ii.  510. 
Ferrein’s,  ii.  510. 
straight,  ii.  510. 
structure  of,  ii.  510. 
varieties  of,  ii,  507. 
veins  of,  ii.  513. 
vessels  of,  ii.  511,  513. 

distribution  of,  ii.  512. 
weight  of,  ii.  506. 

Labia  pudcndi,  ii.  554. 
majora,  ii.  554. 
minora,  ii.  555. 

Labyrinth  or  internal  ear,  ii.  386. 
membranous,  ii.  391. 

. nerves  of,  ii.  173,  393. 
osseous,  ii.  386,  387. 

its  lining  membrane,  ii.  390. 
vessels  of,  ii.  393. 

Lachrymal  apparatus,  ii.  360. 

. canals,  ii.  360. 
caruncula,  ii.  360. 
gland,  ii.  360. 
papilla,  ii.  359. 
puncta,  ii.  360. 
sac,  ii.  361. 

muscle  of,  ii.  361. 

Lacteals,  ii.  45,  456,  459. 

general  anatomy  of,  ii.  44. 

Lactiferous  ducts,  ii.  574. 

Lacuna  magna,  ii.  491. 

Lacunte  of  bone,  i.  77. 

origin  of,  i.  90. 
mucous,  ii.  100. 

Lamellae  of  bone,  i.  76,  79. 

Lamina  cinerea,  ii.  209. 

cribrosa  of  ethmoid,  i.  135. 
sclerotic,  ii.  363. 
temporal  bone,  i.  126. 
vasculosa,  of  retina,  ii.  370. 
spiralis,  of  cochlea,  ii.  388. 
membranacea,  ii.  390. 

Laminated  tubercle,  (cerebellum,)  ii.  226. 

Larynx,  ii.  123. 

articulations  of,  ii.  128. 
cartilages  of,  ii.  124. 

ossification  of,  ii.  140. 
structure  of,  ii.  128. 
development  of,  ii.  139. 
glands  of,  ii.  138. 
interior  of,  ii.  129. 
ligaments  of,  ii.  128. 
mucous  membrane  of,  ii.  138. 
muscles  of,  ii.  133. 

action  of,  ii.  137. 
pouches  of,  ii.  132. 
ventricles,  or  sinuses  of,  ii.  132. 


INDEX. 


623 


Larynx,  vessels  and  nerves  of,  ii.  139. 
vocal  cords  of,  ii.  131. 

Lemniscus,  ii.  237. 

Lens,  crystalline,  ii.  372. 

Lenticular  ganglion,  ii.  266. 
bone,  ii.  383. 

Lienculi,  ii.  500. 

Ligaments,  in  general,  i.  232,  252. 

Ligaments,  acromio-clavicular,  inferior,  i.  264. 
superior,  i.  264. 
alar  of  axis,  i.  258. 
knee,  i.  283. 

annular  of  wrist,  anterior  and  posterior, 
i.  274,  300. 

of  ankle,  anterior,  i.  284. 
internal,  i.  284. 
external,  i.  285. 
of  radius,  i.  268. 
anterior,  of  fingers,  i.  274. 
carpus,  i.  271. 
elbow,  i.  267. 
arcuate,  i.  424. 
aryteno-epiglottic,  ii.  129. 
astragalo-calcaneal,  external,  i.  286. 
interosseous,  i.  286. 
posterior,  i.  286. 
astragalo-scaphoid,  i.  288. 
atlo-axoidean,  anterior,  i.  257. 
posterior,  i.  259. 

of  bladder,  anterior,  i.  306,  ii.  521. 

lateral,  i.  307,  ii.  521. 
calcaneo-cuboid,  internal,  i.  286. 
inferior,  i.  286. 
superior,  i.  286. 
scaphoid,  external,  i.  287. 
inferior,  i.  287. 
capsular  of  hip,  i.  278. 
knee,  i.  281. 
shoulder,  i.  265. 
thumb,  i.  268. 
carpal,  dorsal,  i.  271. 

palmar,  i.  271. 
carpo-metacarpal,  i.  272. 
central  of  spinal  cord,  ii.  191. 
ciliary,  of  eye,  ii.  365. 
coccygeal,  i.  275. 

common  vertebral,  anterior,  i.  252. 

posterior,  i.  252. 
conoid,  i.  264. 

of  larynx,  ii.  128. 
coracoid,  i.  265. 
coraco-acromial,  i.  265. 
clavicular,  i.  264. 
humeral,  i.  265. 
costo-clavicular,  i.  264. 
coracoid,  i.  297. 
sternal  anterior,  i.  262. 

posterior,  i.  262. 
transverse,  anterior,  i.  262. 
middle,  i.  261. 
posterior,  i.  261. 
vertebral,  i.  260. 
xiphoid,  i.  262. 
cotyloid,  i.  278. 
crico-arytenoid,  ii.  129. 

thyroid,  ii.  129. 
crucial,  i.  281. 
cruciform,  i.  257. 
deltoid,  i.  285. 
denticulate,  ii.  252. 
dorsal,  of  carpus,  i.  271. 

metacarpus,  i.  272. 
metatarsus,  i.  290. 


I Ligaments,  tarsus,  i.  289. 
falciform  of  liver,  ii.  470. 
fibular,  anterior,  i.  285. 
middle,  i.  285. 
posterior,  i.  285. 
gastro-lienal,  ii.  497. 
gastro-phrenic,  ii.  447. 

Gimbernat’s,  ii.  591. 
glenoid,  i.  266. 
hyo-epiglottic,  ii.  129. 
ilio-femoral,  i.  278. 

lumbar,  i.  274. 
interarticular,  costal,  i.  261. 

of  hip,  i.  279. 
interclavicular,  i.  2G3. 
interosseous,  astragalo-calcaneal,  i.  286. 
carpal,  i.  271. 
metacarpal,  i.  272. 
calcaneo-cuboid,  i.  287. 
tarsal,  i.  288. 
metatarsal,  i.  290. 
tarso-metatarsal,  i.  289. 
costo-transverse,  i.  261. 
peroneo-tibial,  i.  284. 
inferior,  i.  284. 

interosseous,  radio-ulnar,  i.  268. 
interspinous,  i.  255. 
intertransverse,  i.  256. 
intervertebral,  i.  253. 
lateral,"  of  carpus,  external  and  internal, 
i.  270,  271. 

elbow,  external  and  internal,  i.  266, 
267. 

knee,  external,  i.  279. 
internal,  i.  279. 

maxilla,external  and  internal, i.  259. 
ankle,  external  and  internal,  i.  285. 
fingers,  i.  272,  273. 
toes,  i.  291. 
of  larynx,  ii.  128. 
of  liver,  ii.  476. 
long  plantar,  i.  286. 
metacarpal,  dorsal,  i.  272. 
interosseous,  i.  272 
palmar,  i.  272. 
of  thumb,  i.  272. 
metatarsal,  dorsal,  i.  290. 

plantar,  i.  290. 
mucous,  i.  282. 
of  nucha,  i.  369. 
obturator,  i.  277. 

occipito-atloidean  anterior  and  posterior,  i. 
257,  258. 
axoidean,  i.  258. 
odontoid,  i.  258. 
orbicular,  i.  268. 
ovarian,  ii.  564. 
palmar,  of  carpus,  i.  271. 

fingers,  i.  273. 
of  patella,  i.  280. 
peroneo-tibial,  superior,  i.  283. 

inferior,  i.  284. 
of  phalanges,  fingers,  i.  273. 
toes,  i.  291. 

phrenico-lienal,  ii.  497. 
of  pinna  of  ear,  ii.  375. 
plantar,  long,  i.  286. 
posterior,  of  carpus,  i.  270. 
elbow,  i.  267. 
knee,  i.  280. 

posticum  Winslowii,  i.  280. 
i Poupart’s,  i.  277,  ii.  578. 

processuum  obliquorum,  i.  255. 


624 


INDEX. 


Ligaments,  pterygo-ma.Nillary,  i.  341. 
pubic,  anterior,  i.  277. 

posterior,  i.  277. 
pubo-prostatic,  ii.  521,  526. 
pyramidal,  of  larynx,  ii.  128. 
radio-carpal,  anterior,  i.  270. 

posterior,  i.  270. 
rhomboid,  i.  264. 
round,  of  radius  and  ulna,  i.  269. 
hip,  i.  279. 
liver,  ii.  476. 
uterus,  ii.  563,  572. 

sacro-coccygeal,  anterior  and  posterior,  i. 
274. 

sacro-iliac,  anterior,  i.  276. 
oblique,  i.  276. 
posterior,  i.  276. 
sacro-sciatic,  anterior,  i.  276. 

posterior,  i.  276. 
sacro-vertebral,  i.  274. 
stellate,  i.  261. 
sternal,  i.  262. 

sterno-clavicular,  anterior  and  posterior,  i. 
263. 

stylo-maxillary,  i.  296,  260. 
sub-flavous,  i.  235,  255. 
sub-pubic,  i.  277. 
supra-spinous,  i.  955. 
suspensory,  of  penis,  ii.  529. 

liver,  ii.  476. 
tarsal,  of  eyelid,  ii.  359. 
dorsal,  i.  288. 
plantar,  i.  288. 
tarso-metatarsal,  i.  289. 
teres,  of  hip-joint,  i.  279. 

radio-ulnar,  i.  269. 
of  thumb,  i.  272. 

thyro-arytenoid,  inferior,  and  superior,  ii. 
129. 

thyro-epiglottic,  ii.  129. 
thyro-hyoid,  ii.  128. 
tibio-tarsal,  i.  285. 

transverse,  costal,  external  and  internal,  i. 
261. 

metacarpal,  i.  272. 
metatarsal,  i.  290. 
of  acetabulum,  i.  279. 
atlas,  i.  256. 
knee,  i.  282. 
tibio-fibular,  i.  284. 
of  ankle,  i.  284. 
trapezoid,  i.  265. 
triangular,  i.  277,  305. 

of  urethra,  ii.  600. 
of  tympanic  bones,  ii.  383. 
malleus,  ii.  384. 
incus,  ii.  385. 
stapes,  ii.  385. 
of  uterus,  ii.  562. 

of  uterus,  broad  or  falciform,  ii.  562. 

round,  ii.  563. 
vaginal  of  hand,  i.  274. 
vertebral,  i.  252. 
yellow,  of  spine,  i.  235,  255. 

Ligamentum  latum  pulmonis,  ii.  109. 
arcuatum,  i.  424. 
nuch®,  i.  369. 

Ligature  of  the  brachial  artery,  i.  580. 
carotid,  common,  i.  538. 
iliac,  common,  i.  607. 
external,  i.  618. 
internal,  i.  609. 
femoral,  i.  626. 


Ligature,  subclavian,  i.  561. 

Ligula,  (fourth  ventricle,)  ii.  227. 

Limbus  luteus,  ii.  369. 

Linea  alba,  i.  419. 
aspera,  i.  209. 
splendens,  ii.  253. 

Lips,  ii.  405. 

Liquor  Cotunnii,  ii.  391. 
corneas,  ii.  363. 

Morgagni,  ii.  372. 
sanguinis,  i.  499,  504. 
seminis,  ii.  553. 

Lithotomy,  ii.  604. 

Liver,  ii.  474. 

aberrant  ducts  of,  ii.  486. 
accessory,  ii.  492. 
capillaries  of,  ii.  483. 
cells  or  corpuscles  of,  ii.  485. 
coats  of,  ii.  479. 
congestion  of,  ii.  482. 
development  of,  ii.  491. 
ducts  of,  ii.  478. 

course  of,  ii.  482. 
distribution  of,  ii.  483. 
external  to  liver,  ii.  488. 
excretory  apparatus  of,  ii.  488. 

varieties  of,  ii.  491. 
fissures  of,  ii.  477. 
fcetal  peculiarities  of,  ii.  491. 
fosss  of,  ii.  477. 
hilus  of,  ii.  477. 
ligaments  of,  ii.  476. 
lobes  of,  ii.  477. 
lobules  of,  ii.  480. 

structure  of,  ii.  483. 
lymphatics  of,  ii.  479. 
nerves  of,  ii.  479. 
structure  of,  ii.  479. 
varieties  in  the,  ii.  491. 
vessels  of,  ii.  473. 

course,  ii.  480. 
distribution,  ii.  482. 

vessels  of,  distribution  in  the  foatus,  ii.  491. 
weight  of,  ii.  475. 

Lobes  of  cerebellum,  ii.  226. 
cerebrum,  ii.  221. 
liver,  ii.  477. 
lung,  ii.  111. 

Lobule  of  ear,  ii.  374. 

Lobules  of  glands,  ii.  102. 

particular  glands,  see  those  Glands. 

Lobulus  anonymus,  ii.  477. 
caudatus,  ii.  477. 
quadratus,  ii.  477. 

Spigelii,  ii.  477. 

Locus  niger,  ii.  158,  237. 

perforatus,  anterior,  ii.  210. 
posterior,  ii.  208. 

Luette  vesicale,  ii.  522. 

Lunul®  of  nails,  ii.  88. 

valves  of  heart,  i.  478. 

Lungs,  ii.  110. 

air-cells  of,  ii.  117. 
tubes  of,  ii.  116. 

subdivision  of,  ii.  116. 
capacity  of,  ii.  111. 
capillaries  of,  ii.  120. 
cellular  tissue  of,  ii.  114. 
changes  at  birth,  ii.  123. 
colour  of,  ii.  113. 
development  of,  ii.  122. 
fissures  of,  ii.  111. 
fetal,  ii.  122. 


INDEX. 


625 


Lungs,  form  of,  ii.  110. 

gravity,  specific,  of,  ii.  112. 
lobes  of,  ii.  111. 
lobules  of,  ii.  113. 

structure  of,  ii.  113. 
lymphatics  of,  ii.  122. 
nerves  of,  ii.  122. 
root  of,  ii.  115. 
size  and  weight  of,  ii.  112. 
structure  of,  ii.  113. 
texture  of,  ii.  112. 
vessels  of,  pulmonary,  ii.  114. 
bronchial,  ii.  114. 

Lymph,  ii.  33. 

corpuscles,  ii.  34. 
plasma  of,  ii.  34. 
duct,  right,  ii.  47. 

Lymphatic  System,  General  Anatomy  of,  ii.  33. 
glands,  ii.  41,  49. 

structure  of,  ii.  41. 
uses  of,  ii.  42. 
hearts,  ii.  43. 
outline  of,  ii.  44. 
vessels,  ii.  37.  ■ 

afferent,  ii.  41. 
coats  of,  ii.  39. 
development  of,  ii.  44. 
distribution  of,  ii.  37. 
efferent,  ii.  41. 
lacteal,  ii.  44. 
origin  of,  ii.  38. 

Lymphatic  vessels,  plexus  of,  ii.  38. 
structure  of,  ii.  39. 
termination  of,  ii.  42. 
valves  of,  ii.  40. 
vessels  and  nerves  of,  ii.  40. 
vital  properties  of,  ii.  40. 

Lymphatics,  Descriptive  Anatomy  of,  ii.  44. 
of  the  abdomen,  ii.  50. 
arm,  ii.  56. 
bladder,  ii.  51. 
head,  ii.  57.  ‘ 
heart,  ii.  55. 

intestines,  small,  ii.  53,  459. 
kidneys,  ii.  52. 
leg,  ii.  49. 
limb,  lower,  ii.  47. 

upper,  ii.  56. 
liver,  ii.  52. 
loins,  ii.  52. 
lungs,  ii.  54. 
mesentery,  ii.  45. 
neck,  ii.  58. 
oesophagus,  ii.  55. 
pancreas,  ii.  52. 
pelvic  viscera,  ii.  51. 
pelvis,  ii.  50. 
penis,  ii.  51. 
rectum,  ii.  51. 
scrotum,  ii.  51. 
spleen,  ii.  52. 
stomach,  ii.  52. 
testicle,  ii.  51. 
thorax,  ii.  54. 
thymus  gland,  ii.  55. 
thyroid  gland,  ii.  55. 
uterus,  ii.  51. 

Lyra,  ii.  216. 

Macula  germinativa,  ii.  565. 

Malleolus,  external,  i.  216. 
internal,  i.  214. 

Malleus,  ii.  381. 

VOL.  II. 


Malpighian  corpuscles,  kidney,  ii.  509,  512. 
spleen,  ii.  499. 

Mammae,  ii.  574. 
structure,  ii.  574. 
varieties,  ii.  576. 
vessels  and  nerves,  ii.  579. 

Manubrium,  i.  170. 

Margaric  and  stearic  acids,  i.  47. 

Margarin,  i.  47. 

Marrow  of  bone,  i.  80. 

Mastoid  cells,  ii.  380. 

Massa  vel  moles  carnea,  i.  458. 

Matrix,  see  Uterus, 
of  nail,  ii.  88. 

Meatus,  auditory,  external,  i.  125,  ii.  376. 
auditory,,  internal,  i.  126. 
of  nose,  inferior,  i.  162,  ii.  401. 
middle,  i.  137,  162,  ii.  401. 
superior,  i.  137,  162,  ii.  401. 
urinarius,  female,  ii.  524,  556. 
male,  ii.  536. 

Mediastinum,  anterior,  i.  469,  ii.  109. 
posterior,  i.  459,  ii.  109. 
testis,  ii.  546. 

Medulla  of  bone,  i.  80. 

Medulla  oblongata,  ii.  197. 

back  of,  ii.  200,  226. 
columns  of,  ii.  197. 

course  of,  ii.  230. 
gray  matter  of,  ii.  156,  232. 
internal  structure  of,  ii.  230. 
weight  of,  ii.  189. 
spinalis,  ii.  190. 

Medullary  substance  of  kidney,  ii.  508,  509. 

Meibomian  glands,  ii.  359. 

Membrana  adamantina,  ii.  422. 
fusca,  ii.  364. 
nictitans,  ii.  360. 
pupillaris,  ii.  368. 
sacciformis,  i.  270. 
tympani,  ii.  378. 

Membrane  of  aqueous  humour,  ii.  363,  370. 
arachnoid,  ii.  251. 
capsulo-pupillary,  ii.  373. 
choroid,  ii.  364. 
costo-coracoid,  i.  297. 
crico-thyroid,  i.  128. 
hyaloid,  ii.  370. 

Jacob’s,  ii.  369. 
pituitary,  ii.  399. 
thyro-hyoid,  ii.  128. 

Schneiderian,  ii.  399. 

Membranes  of  the  brain  and  spinal  cord,  ii.  247. 
development  of,  ii.  258. 
mucous,  serous,  &c.,  see  Serous  mem- 
branes, Mucous  membranes,  &c. 

Membranous  labyrinth,  ii.  391.,. 
portion  of  urethra,  ii.  535. 

Meninges,  ii.  247. 

Mesenteric  glands,  ii.  245. 

Mesenteries,  ii.  502,  504. 

Mesentery,  ii.  454,  502. 
development  of,  ii.  473. 

Meso-ceecum,  ii.  464,  503. 
colon,  ii.  467,  503. 
rectum,  ii.  468,  503. 

Mesorchium,  ii.  543,  57i. 

Metacarpus,  i.  193,  197. 

Metatarsus,  i.  221,  226. 

Milk-teeth,  ii.  405. 

Modiolus,  ii.  389. 

Molar  teeth,  ii.  408. 
glands,  ii.  405. 


53 


626 


INDEX. 


Mons  veneris,  ii.  554. 

Morsiis  diaboli,  ii.  566. 

Mouth,  ii.  404. 

Mucous  membranes,  general  anatomy  of,  ii.  78. 
alveoli  of,  ii.  82. 
attachment  of,  i.  78. 
basement  membrane  of,  ii.  80. 
corium  of,  ii.  79,  80. 
divisions  of,  ii.  78. 
epithelium  of,  ii.  62,  79. 
iolds  and  valves  of,  ii.  79. 
follicles  of,  ii.  82. 
gastro-pulmonary,  ii.  78. 
genito-urinary,  ii.  78. 
glands  of,  compound^  ii.  82. 
simple,  ii.  82. 
mammary,  ii.  78. 
nerves  of,  ii.  83. 
papillae  of,  ii.  81. 
physical  properties  of,  ii.  79. 
regeneration  of,  ii.  83. 
secretion  of,  ii.  83. 
structure  of,  ii.  79. 
tubuli  of,  ii.  82. 
vessels  of,  ii.  81. 
villi  of,  ii.  81. 

Mucus,  ii.  83. 

Multicuspidate  teeth,  ii.  408. 

Multilocular  crypts,  ii.  101. 

Muscles,  contraction  of,  i.  325. 

origin  and  insertion  of,  i.  314,  319. 
penniform,  i.  315. 
semi-penniform,  i.  315. 
sheaths  of,  i.  314. 
structure  of,  i.  313. 

Muscles,  Descriptive  Anatomy  of,  i.  331. 
tables  of,  i.  462. 
abdominal,  i.  413. 
abductor  digit!  minimi,  i.  410. 
pedis,  i.  457. 
indicis,  i.  411. 

oculi  (rectus  externus),  i.  347. 
pollicis,  i.  408. 
pedis,  i.  457. 

accelerator  urinae,  ii.  538. 
accessorii  orbicularis,  i.  341. 
accessorius  (pedis),  i.  458. 

ad  sacro-lumbalem,  i.  376. 
adductor  brevis,  i.  458. 
adductor  digiti  minimi,  i.  410. 
longus,  i.  441. 
magnus,  i.  441. 
oculi  (rectus  internus),  i.  347. 
pollicis,  i.  409. 
pedis,  i.  459. 
anconeus,  i.  404. 
anti-tragicus,  ii.  375. 
of  anus.  ii.  469. 
arm,  i.  389. 
arytaenoideus,  ii.  137. 
arytseno-epiglottideus,  ii.  136. 
attollens  auriculam,  i.  334. 

oculum  (rectus  or  superior),  i.  347. 
attrahens  aurem  (anterior),  i.  334. 
auriculares,  superior,  posterior,  et  anterior, 
i.  334. 

auygos  uvulae,  i.  365. 
of  back,  i.  366. 
basio-glossus,  i.  355. 
biceps  femoris,  i.  443. 

flexor  cubiti,  i.  392. 
biventer  ce.rvicis,  i.  379. 
maxiilaris,  i.  352. 


Muscles,  brachialis  anticus,  i.  394. 
buccinator,  i.  341. 
bulbo-cavernosus,  ii.  538. 
caninus,  i.  339. 
cerato-glossus,  i.  355. 
cervicalis  ascendens  vel  descendens,  i.  376. 
chondro-glossus,  i.  355. 
ciliaris,  i.  355. 
circumflex  palati,  i.  365. 
coccygeus,  ii.  472. 
complexus,  i.  378. 

minor,  i.  378. 
compressor  naris,  i.  338. 
sacculi  laryngis,  ii.  136. 
urethras,  ii.  538. 
venae  dorsalis,  penis,  ii.  538. 
constrictor  pharyngis,  inferior,  i.  362. 
medius,  i.  362. 
superior,  i.  363. 
isthmi  faucium,  i.  366. 
vaginae,  ii.  559. 
coraco-brachialis,  i.  392. 

hyoideus,  i.  356. 
corrugator  supercilii,  i.  336. 
cremaster,  ii.  541. 

crico-arytaenoideus  lateralis,  ii.  134. 
posticus,  ii.  134. 
thyroideus,  i.  357,  ii.  135. 
crureus,  i.  438. 
cucullaris,  i.  367. 
deltoides,  i.  388. 
depressor  anguli  oris,  i.  340. 

Muscle,  depressor  epiglottidis,  ii.  136. 
labii  inferions,  i.  340. 

inferioris  alaeque  nasi,  i.  338. 
oculi  (rectus  inferior),  i.  347. 
detrusor  urinae,  ii.  523. 
diaphragma,  i.  422. 
digastricus,  i.  352. 
dilatator  naris,  anterior,  i.  337. 

posterior,  i.  338. 
of  ear,  external,  i.  334,  ii.  375. 

internal,  ii.  387. 
ejaculator  seminis,  ii.  538. 
erector  clitoridis,  ii.  555. 
penis,  ii.  537. 
spinae,  i.  375. 

extensor  carpi  radialis  brevior,  i.  403. 
longior,  i.  403. 
ulnaris,  i.  405. 
coccygis,  i.  381. 
cruris,  i.  436. 
digiti  minimi,  i.  405. 
digitorum  brevis  pedis,  i.  447. 
communis,  i.  404. 
longus  pedis,  i.  446. 
indicis,  i.  407. 

ossis  metacarpi  pollicis,  i.  405. 
primi  internodii  pollicis,  i.  406. 
pollicis  proprius,  i.  446. 
secundi  internodii  pollicis,  i.  406. 
of  eye,  i.  346. 
face,  i.  334. 

flexor  accessorius,  i.  458. 

brevis  digiti  minimi,  i.  410. 

pedis,  i.  460. 
digitorum  pedis,  i.  457. 
carpi  radialis,  i.  397. 

ulnaris,  i.  398. 
digitorum  profundus,  i.  400. 

sublimis,  i.  398. 
longus  digitorum  pedis,  i.  453. 
pollicis  pedis,  i.  454. 


INDEX. 


627 


Muscle,  pollicis  brevis,  i.  409. 
pedis,  i.  458. 
longus,  i.  401. 
of  foot,  i.  456. 

forearm,  i.  393. 
gastrocnemius,  i.  450. 
gemellus  inferior,  i.  433. 

superior,  i.  433. 
genio-hyo-glossus,  i.  355. 

hyoideus,  i.  354. 
glutaeus  maximus,  i.  429. 

medius,  i.  430. 
glutsBus  minimus,  i.  430. 
gracilis,  i.  440. 

Guthrie’s,  ii.  537. 
of  hand,  i.  407. 
head,  i.  331. 
hip,  i.  428. 
helicis  major,  ii.  375. 

minor,  ii.  375. 

Houston’s,  ii.  537. 
hyo-glossus,  i.  354. 
iliacus,  i.  427. 
indicator,  i.  407. 
infra-costales,  i.  421. 
infra-spinalus,  i.  390. 
inter-costales  extern!,  i.  421. 
intern!,  i.  421. 

inter-ossei  manus  dorsales,  i.  411. 
palmares,  i.  411. 
pedis  dorsales,  i.  460. 
plantares,  i.  460. 
inter-spinales,  i.  381. 
inter-transversales,  i.  382. 
ischio-cavernosus,  ii.  537. 
of  larynx,  ii.  133. 

action  of,  ii.  123. 
latissimus  dorsi,  i.  369. 

Isixator  tympani  major,  ii.  384. 

minor,  ii.  384. 
of  leg,  i.  426. 
levator  anguli  oris,  i.  339. 
scapulae,  i.  372. 
ani,  ii.  471. 

glandulae  thyroideae,  ii.  140. 
labii  inferioris,  i.  340. 

superioris,  i.  339. 
alaeque  nasi,  i.  337. 
menti,  i.  340. 

.oculi,  i.  347. 
palati,  i.  365. 
palpebrae,  i.  336. 

proprius  alse  nasi,  posterior,  i.  338. 

anterior,  i.  339. 
prostatas,  ii.  471,  526. 
uvulae,  i.  365. 
levatores  costarum,  i.  422. 
lingualis,  ii.  432. 

superficialis,  ii.  433. 
transversus,  ii.  433. 
longissimus  dorsi,  i.  377. 
longus  colli,  i.  360. 
of  lower  limb,  i.  426. 
lumbricales  manus,  i.  401. 
pedis,  i.  458. 

mallei  externus  (laxator  tympani,  major), 
ii.  384. 

internus,  ii.  384. 
masseter,  i.  343. 
multifidus  spinae,  i.  380. 
mylo-hyoideus.  i.  354. 
myrtiformis,  i.  338. 
naso-labialis,  i.  342. 


Muscle,  of  neck,  i.  349. 
nose,  ii.  399. 

obliquus  abdominis  externus,  i.  414,  ii. 

578. 

internus,  i.  259,  416. 
auris,  ii.  376. 
capitis  inferior,  i.  382. 
superior,  i.  382. 
oculi  inferior,  i.  348. 
superior,  i.  347. 
obturator  externus,  i.  434. 

internus,  i.  432. 
occipito-frontalis,  i.  332. 
omo-hyoideus,  ii.  13. 
opponens  digit!  minimi,  i.  410. 

pollicis,  i.  409. 
orbicularis  latus,  i.  335. 
oris,  i.  341-. 
palpebrarum,  i.  335. 
of  palate,  i.-364. 
palato-glossus,  i.  366. 

pharyngeus,  i.  366. 
palmaris  brevis,  i.  410. 

longus,  i.  398. 
pectineus,  i.  440. 
pectoralis  major,  i.  385. 

minor,  i.  386. 
of  penis,  ii.  537. 

perinaeum,  ii.  442,  598. 
peroneus  brevis,  i.  448. 
longus,  i.  448. 
tertius,  i.  447. 
of  pharynx,  i.  362,  ii.  442. 
plantaris,  i.  451. 
platysma  myoides,  i.  350. 
popliteus,  i.  453. 
posterior  auris,  i.  334. 
pronator  quadratus.  i.  401. 

radii  teres,  i.  396. 
psoas  magnus,  i.  426. 
parvus,  i.  428. 

pterygoidens  externus,  i.  345. 

internus,  i.  345. 
pubo-urethrales,  ii.  539. 
pyramidales  abdominis,  i.  418. 

nasi,  i.  337. 
pyriformis,  i.  432. 
quadratus  femoris,  i.  434. 
lumborum,  i.  419. 
menti,  i.  340. 
quadriceps  cruris,  i.  437. 
rectus  abdominis,  i.  418. 

capitis  anticus  major,  i.  360. 
minor,  i.  360. 
posticus  major,  i.  381. 
minor,  i.  382. 
femoris,  i.  437. 
lateralis,  i.  360. 
oculi  externus,  i.  347. 
inferior,  i.  347. 
internus,  i.  347. 
rectus  oculi  superior,  i.  347. 
retrahens  auriculam,  i.  334. 
rhomboideus  major,  i.  371. 

minor,  i.  372. 
risorius,  i.  341. 
rotatores  spinae,  i.  381. 
sacro-coccygis,  i.  381. 

lumbalis,  i.  376. 
salpingo-pharyngeus,  i.  363. 
sartorius,  i.  436. 

Santorini’s,  i.  341. 
scalenus  anticus,  i.  358. 


INDEX, 


628 

Muscle,  scalenus  medius,  i.  358. 
posticus,  i.  359. 
semi-spinalis  colli,  i.  380. 
dorsi,  i.  380. 

semi-membranosus,  i.  444. 
senii-tendinosus,  i.  443. 
serratus  magnus,  i.  387. 
posticus  inferior,  i.  373. 
superior,  i.  373. 
soleus,  i.  450. 

sphincter  ani  e.xternus,  ii.  470. 
internus,  ii.  470. 
pupilltE,  ii.  366. 
vaginae,  ii.  558. 
vesicse,  ii.  523. 
spinalis  dorsi,  i.  378. 

cervicis,  i.  378. 
splenius  capitis,  i.  373. 

colli,  i.  373. 
stapedius,  ii.  385. 
sterno-cleido-mastoideus,  i.  350. 
hyoideus,  i.  35G. 
thyroideus,  i.  356. 
stylo-glossus,  i.  353. 
hyoideus,  i.  353. 
pharyngeus,  i.  353. 
subclavius,  i.  387. 
subcrureus,  i.  439. 
subscapularis,  i.  391. 
superior  auris,  i.  334. 
supinator  radii  brevis,  i.  407. 

longus,  i.  402. 
supra-spinatus,  i.  390. 
temporal,  i.  344. 
tensor  fasciae  latae,  i.  435. 
palati,  i.  365. 
tarsi,  i.  337. 
tympani,  ii.  384. 
vaginae  femoris,  i.  435. 
teres  major,  i.  390. 

minor,  i.  390. 
of  thigh,  i.  435. 
thyro-arytaenoideus,  ii.  135. 
epiglottideus,  i.  136. 
hyoideus,  i.  357. 
tibialis  anticus,  i.  445. 

posticus,  i.  455. 
of  tongue,  ii.  433. 
trachelo-mastoideus,  i.  378. 
tragicus,  ii.  375. 

transversalis  abdominis,  i.  417,  ii.  580. 
cervicis,  i.  377. 
masi,  i.  338. 

transversus  auriculae,  ii.  375. 
pedis,  i.  460. 
perinaei,  ii.  538. 
alter,  ii.  538. 
trapezius,  i.  367. 
triangularis  oris,  i.  340. 
sterni,  i.  422. 

triceps  extensor  cruris,  i.  437. 

cubiti,  i.  394. 
trochlearis,  ii.  347. 
of  tympanum,  i.  384. 
upper  limb,  i.  384. 
ureters,  ii.  523. 
urethra,  ii.  508. 
vastus  externus,  i.  438. 

internus,  i.  438. 

Wilson’s,  ii.  539. 
zygomaticus  major,  i.  339. 
minor,  i.  339. 

Muscular  contractility,  i.  313,  325. 


Muscular  sound,  i.  326. 

tissue,  general  anatomy  of,  i.  313. 
chemical  nature  of,  i.  322. 
connexion  with  tendons,  i.  319. 
development  of,  i.  323. 
elementary  particles  of,  i.  316. 
fasciculi  of,  i.  314. 
fibres  of,  i.  315. 
filaments  of,  i.  316. 
of  heart,  i.  322,  482. 
involuntary  or  plain,  i.  321. 
nerves  of,  i.  320. 
regeneration  of,  i.  324. 
striae  of,  i.  315. 
vessels  of,  i.  320. 
vital  properties  of,  i.  324. 
voluntary,  or  striped,  i.  313. 

Musculi  papillares,  left  ventricle,  i.  479. 
right  ventricle,  i.  476. 
pectinati,  left  auricle,  i.  478. 
right  auricle,  i.  473. 

Nails,  ii.  88. 

growth  of,  ii.  89. 
matrix  of,  ii.  88. 
reproduction  of,  ii.  89. 

Nares,  anterior,  i.  162,  ii.  396,  399. 
posterior,  i.  156,  ii.  396. 
septum  of,  i.  162,  ii.  396. 

Nasal  cartilages,  ii.  397. 
duct,  ii.  361. 

Nates  (of  brain),  ii.  223. 

Nerves,  general  anatomy  of,  ii.  163. 
cerebro-spinal,  ii.  163. 

Nerve,  cerebro-spinal  afferent,  ii.  147. 
branches  of,  ii.  165. 
communications  of,  ii.  165. 

with  sympathetic,  ii.  178. 
compound,  ii.  175. 

connexion  with  nervous  centre,  ii. 

155,  167. 
ganglia,  ii.  162. 
development  of,  ii.  183. 
efferent,  ii.  147. 

extremities,  peripheral  of,  ii.  168. 
fasciculi  of,  ii.  163. 
funiculi  of,  ii.  163. 
fibres  of,  ii.  164. 
intracranial  portions  of,  ii.  168. 
motor,  ii.  182. 
nerves  of,  ii.  165. 
neurilemma  of,  ii.  163. 
organic  influence  of,  ii.  182. 
origins  of,  ii.  166,  229. 
apparent,  ii.  166. 
real  or  deep,  ii.  229. 
peculiarities  of,  ii.  174. 
plexuses  of,  ii.  165.  (See  Plexuses  of 
nerves.) 
reflex,  ii.  181. 

relation  of,  to  sympathetic,  ii.  177. 
reunion  of,  ii.  184. 
roots  of,  ii.  166,  182. 
motor,  ii.  167. 
sensory,  ii.  167. 
sensory,  ii,  182. 
sheaths  of,  ii.  164. 
simple,  ii,  183. 
structure  of,  ii.  148. 
terminations  of,  ii.  168. 

in  ciliary  ligament,  ii.  169. 
electric  organs,  ii.  173. 
internal  ear,  ii.  173. 


INDEX. 


629 


Nerve,  termination  of,  in  iris,  ii.  169. 

muscles,  i.  320,  ii.  168. 
nose,  ii.  173. 

Pacinian  bodies,  ii.  172. 
retina,  ii.  173. 
skin,  frog,  ii.  169. 
man,  ii.  88. 
tadpole,  ii.  169. 
teeth,  ii.  173. 
tongue,  ii.  773. 
vessels  of,  i.  16.6. 

cerebro-spinal,  vital  properties  of,  ii.  181. 
sympathetic,  ii.  175. 

constitution  of,  ii.  180. 
differences  in,  ii.  176. 
general  character  of,  ii.  175. 
relation  to  cerebro-spinal  nerves,  ii. 
177. 

relation  to  roots  of  spinal  nerves,  ii. 
180. 

structure  of,  ii.  176. 

Nerves,  descriptive  anatomy  of,  ii.  185. 

Nerv.  abducent,  ii.  246,  278. 

Nerve,  accessory,  spinal,  ii.  247. 

accessory  to  obturator,  ii.  325.  • 

acromial,  ii.  304. 

articular,  of  shoulder  joint,  ii.  307,  309. 
elbow  joint,  ii.  312. 
hip  joint,  ii.  324,  336. 
knee,  ii.  324,  334,  337. 
auditory,  ii.  247,  282,  393. 
auricular,  anterior,  ii.  274. 
great,  ii.  289,  303. 
posterior,  ii.  280. 

auricular,  of  auriculo-temporal,  ii.  274. 
par  vagum,  ii.  289. 
second  cervical,  ii.  298. 
auriculo-temporal,  ii.  264. 
axillary,  ii.  308. 
buccal,  or  buccinator,  ii.  273. 

of  facial,  ii.  282. 
cardiac,  inferior,  ii.  345. 
middle,  or  deep,  ii.  344. 
pneumogastric,  ii,  290,  291. 
superior,  or  superficial,  ii.  342. 
cavernous,  of  penis,  ii.  355. 
cervical,  divisions  of,  anterior,  ii.  301.  306. 
posterior,  ii.  297. 

. superficial,  ii.  302. 
cervico-facial,  ii.  282. 
chorda  tympani,  ii.  280. 
ciliary,  long,  ii.  266,  367. 

short,  ii.  265,  367. 
circumflex  of  arm,  ii.  308. 
clavicular,  ii.  304. 

coccygeal,  divisions  of  anterior,  ii.  330. 

posterior,  ii.  361. 
cochlear,  ii.  396. 
communicans  tibiae,  ii.  335. 

peronei,  ii.  335-37. 
of  Cotunnius,  ii.  211. 
cranial,  see  Cranial  Nerves, 
crural,  anterior,  ii.  325. 

internal,  ii.  324. 
cutaneous,  radial,  ii.  316. 
ulnar,  ii.  312. 

abdominal,  anterior,  ii.  320. 

lateral,  ii.  319. 
external,  of  arm,  ii.  311. 

(median),  ii.  315. 
of  thigh,  ii.  323. 
internal,  of  arm,  ii.  309. 


I Nerve,  internal,  small,  ii.  309. 

(median),  ii.  316. 
of  thigh,  ii.  326. 
middle,  of  thigh,  ii.  326. 
obturator,  ii.  324. 
plantar,  ii.  336. 
thoracic,  anterior,  ii.  318. 
lateral,  ii.  3lk 
dental,  anterior,  ii.  269. 
inferior,  ii.  276. 
posterior,  ii.  269. 
descendens  noni,  ii.  293. 
diaphragmatic,  ii.  304. 
digastric,  ii.  280. 

digital,  on  dorsum  of  foot,  ii.  338. 
hand,  ii.  312. 
median,  ii.  314. 
plantar,  ii.  336. 
radial,  ii.  316. 
ulnar,  ii.  312. 

dorsal,  divisions  of,  anterior,  ii.  317. 
posterior,  ii.  299. 
of  penis,  ii.  331. 
dorsi-lumbar,  ii.  318,  320. 
of  dura  mater,  ii.  262,  264. 
facial,  ii.  246,  279. 
of  femoral  artery,  ii.  326. 
frontal,  ii.  265. 
of  gall-bladder,  ii.  352. 
gastric,  ii.  291,  452. 
genito-crural,  ii.  323. 
glosso-pharyngeal,  ii.  247,  283. 
gluteal,  inferior,  ii.  332. 

superior,  ii.  320. 
gustatory,  ii.  275. 
heemorrhoidal  inferior,  ii.  332,  354. 

superior,  ii.  353. 
of  heart,  ii.  350. 
hepatic,  ii.  353. 

hypo-glossal,  ii.  247,  292,  294. 
ilio-hypogastric,  ii.  322. 

inguinal  or  ilio-scrotal,  ii.  322. 
infra-maxillary,  ii.  273,  282. 
orbital,  ii.  269,  282. 

of  facial,  ii.  282. 
trochlear,  ii.  266. 
inguino-cutaneous,  ii.  323. 
intercostal,  ii.  317. 
lower,  ii.  319. 
upper,  ii.  317. 

intercosto-humeral,  ii.  319. 
inter-osseous  anterior,  ii.  313. 

posterior,  ii.  316. 
of  intestines,  ii.  352. 
ischiadic,  great,  ii.  333. 

small,  ii.  332. 

Jacobson’s,  ii.  284. 
labial,  ii.  270,  276. 
of  labyrinth,  ii.  393. 
lachrymal,  ii.  265. 
of  Lancisi,  ii.  212. 
laryngeal,  external,  ii.  289. 

inferior,  or  recurrent,  ii.  290. 
superior,  ii.  289. 
lingual,  ii.  285,  292, 
of  fifth,  ii.  275. 

glosso-pharyngeal,  ii.  285. 
lumbar,  divisions  of,  posterior,  ii.  300. 

anterior,  ii.  320. 
lumbo-sacral,  ii.  320,  330. 
malar,  subcutaneous,  ii.  269. 
of  facial,  ii.  281. 


53* 


630 


INDEX. 


Nerve,  masseteric,  ii.  273. 

maxillary,  inferior,  ii,  273,  276. 

superior,  ii.  268,  272. 
median,  ii.  313. 
mental,  ii.  277. 

motor  of  eye,  common,  ii.  245,  260. 

external,  ii.  246,  278. 
musculo-cutaneous,  ii.  310. 
of  leg,  ii.  333. 
spiral,  ii.  315. 
mylo-hyoid,  ii.  276. 
nasal,  ii.  266,  269. 

of  spheno-palatine  ganglion,  ii.  271. 
vidian  nerve,  ii.  272. 
naso-palatine,  ii.  271,  402. 
obturator,  ii.  324. 
occipital  (of  facial),  ii.  280. 
great,  ii.  298. 
of  third  cervical,  ii.  298. 
small,  ii.  303. 
oculo-nasal,  ii.  266. 
oesophageal,  ii.  291. 
olfactory,  ii.  168,  243,  402. 
ophthalmic,  ii.  263. 
optic,  ii.  168,  244,  260,  368. 
orbital,  ii.  268. 
ovarian,  ii.  355. 

palatine,  anterior  or  larger,  ii.  271. 
external,  ii.  271. 
posterior  or  smaller,  ii.  271. 
palmar  cutaneous,  ii.  314. 
ulnar,  deep,  ii.  312. 
superficial,  ii.  312. 
palpebral,  ii.  209,  269. 
pathetic,  ii.  245,  262. 
perforans  Casserii,  ii.  310. 
perineal,  ii.  331. 
peroneal,  ii.  337. 

petrosal,  superficial,  large,  ii.  272. 

external  (sympathetic),  ii.  280. 

in  the  figure,  ii.  284. 
small,  ii.  285. 
pharyngeal,  ii.  272,  341. 

of  glosso-pharyngeal,  ii.  285,  289. 
phrenic,  ii.  304. 
plantar,  external,  ii.  336. 
internal,  ii.  336. 

pneumogastric,  ii.  247,  285,  286,  288. 
popliteal,  external,  ii.  337. 

internal,  ii.  334. 
portio  dura,  ii.  246,  278,  279. 

mollis,  ii.  247,  278,  282. 
pterygoid,  ii.  272. 
pudendal,  inferior,  ii.  332. 
pudic,  ii.  331. 

pulmonary,  of  pneumogastric,  ii.  291. 
radial,  ii.’3I6. 

recurrent,  laryngeal,  ii.  290. 
renal,  ii.  351. 

posterior,  ii.  347. 
respiratory,  external,  ii.  306. 
sacral,  divisions  of,  anterior,  ii.  329. 
posterior,  ii.  300. 

saphenous,  long,  or  internal,  ii.  327. 

short,  or  external,  ii.  334. 
sciatic,  great,  ii.  333. 

small,  ii.  332. 
spermatic,  ii.  351. 
spheno-palatine,  ii.  269,  270. 
spinal,  ii.  294.  (See  spinal  nerves.) 
accessory,  ii.  247,  292. 
splanchnic,  great,  ii.  346. 


Nerve,  small,  ii.  347. 

smallest,  ii.  347. 
splenic,  ii.  352. 
stylo-hyoid,  ii.  280. 
subcutaneous,  of  neck,  ii.  282. 

malar,  ii.  269. 
sub-occipital,  ii.  298,  301. 
sub-scapular,  ii.  308. 
supia-clavicular,  ii.  304. 
superficial  cervical,  ii.  302. 

cardiac,  ii.  342. 
supra-maxillary,  ii.  282. 
supra-orbital,  ii.  265. 
scapular,  ii.  307. 
trochlear,  ii.  265. 

sympathetic,  see  sympathetic  nerves,  ii. 

175,  339. 

temporal,  deep,  ii.’  273. 
of  facial,  ii.  281. 

superficial,  ii.  274,  275. 
temporo-malar,  ii.  268. 
temporo-facial,  ii.  281. 

malar,  ii.  268. 
thoracic,  anterior,  ii.  308. 

• posterior,  ii.  307. 

thyroid,  ii.  344. 
tibial,  anterior,  ii.  338. 

posterior,  ii.  335. 
tonsillar,  ii.  285,  436. 
trifacial,  or  trigeminal,  ii.  245,  263. 
trochlear,  ii.  245,  262. 
tympanic,  ii.  284. 
of  tympanum,  ii.  385. 
ulnar,  ii.  311. 

of  Wrisberg,  ii.  309. 
uterine,  ii.  356,  357. 

in  gravid  state,  ii.  356. 
vaginal,  ii.  356. 
vagus,  ii.  247,  285. 
of  vas  deferens,  ii.  356. 

vesiculae  seminales,  ii.  356. 
vestibular,  ii.  295,  396. 
vidian,  ii.  272. 

Nerve-cells,  corpuscles  or  vesicles,  ii.  153. 
development  of,  ii.  184. 
of  encephalon,  ii.  158. 
ganglia,  ii.  162. 
spinal  cord,  ii.  156. 
office  of,  ii.  181. 

Nerve-fibres,  ii.  148. 
afferent,  ii.  181. 
axis  of,  ii.  149. 

of  cerebro-spinal  nerves,  ii.  164. 
development  of,  ii.  183. 
efferent,  ii.  181. 
of  encephalon,  ii.  157. 
of  ganglia,  ii.  162. 
gelatinous,  ii.  150. 

nature  of,  ii.  176. 
office  of,  ii.  181. 
origin  of,  in  gray  matter,  ii.  157. 

ganglia,  ii.  161. 
of  particular  nerves,  ii.  174. 
spinal  cord,  ii.  156. 
sympathetic  nerves,  ii.  176. 
tubular,  ii.  149. 
varicose,  ii.  151. 

Nervi  molles,  ii.  343. 

Nervous  system,  general  anatomy  of,  ii.  146. 
cerebro-spinal  centre  of,  ii.  155. 

nerves  of,  ii.  147. 
divisions  or  parts  of,  ii.  147. 


INDEX. 


631 


Nervous  system,  functions  of,  ii.  146. 
ganglia  of,  ii.  161 . 
sympathetic  portion  of,  ii.  176. 
vital  properties  of,  ii.  181. 
descriptive  anatomy  of,  ii.  185. 
cerebro-spinal  axis,  ii.  185. 
cranial  nerves,  ii.  259. 
spinal  nerves,  ii.  294. 
sympathetic  nerve,  ii.  339. 

Nervous  substance,  ii.  147. 

cells  or  corpuscles  of,  ii.  153. 
of  cerebro-spinal  centre,  ii.  155. 
chemical  nature  of,  ii.  148. 
of  encephalon,  gray,  ii.  228. 
white,  li.  228. 

fibres  of,  gelatinous,  ii.  152. 
tubular,  ii.  149. 
varicose,  ii.  151. 
of  ganglia,  ii.  161. 
spinal  cord,  gray,  ii.  155. 

white,  ii.  156. 
spinal  nerves,  ii.  164. 
structure  of,  ii.  148. 
of  sympathetic,  ii.  167. 
vesicles  of,  ii.  153. 

Nervus  impar,  ii.  192. 

Neurilemma,  ii.  164. 
of  cord,  ii.  250. 

Nipple,  ii.  574. 

Nodule,  cerebellum,  ii.  226. 

Noduli  arantii,  i.  478,  481. 

Nodus  encephali,  ii.  201. 

Nose,  ii.  396. 

alae  of,  ii.  398. 

bones  of  i.  144,  161,  ii.  397. 

cartilages  of,  ii.  397. 

fossae  of,  i.  161,  399. 

mucous  membrane  of,  ii.  400. 

muscles  of,  ii.  399. 

nerves  of,  ii.  173,  402. 

septum  of,  i.  162,  ii.  396. 

skin  of,  ii.  399. 

vessels  of,  ii.  401, 

Notch,  cotyloid,  i.  203. 

sacro-sciatic,  great  and  small,  i.  205. 
sigmoid,  i.  150. 

Nuclear  fibres,  i.  67. 

Nucleolus,  i.  55. 

Nucleus,  i.  55. 

changes  in,  i.  67. 
division  of,  i.  58. 
origin  of,  i.  58. 

Nutrition  of  textures,  i.  68. 

Nutritive  secretion,  ii.  97. 

Nymphae,  ii.  555. 

(Esophagus,  ii.  442. 

development  of,  ii.  473. 

Olecranon,  i.  188. 

Oleic  acid,  and  Olein,  i.  48. 

Olfactory  bulb  and  nerve,  ii.  243,  260,  402. 

Olives,  or  Olivary  bodies,  ii.  199,  232. 

Omenta,  ii.  501. 

Omentum,  gastro-hepatic,  ii.  502,  448. 
gastro-colic,  ii.  501,  448. 
gastro-splenic,  ii.  502,  448. 
great,  ii.  502. 
small,  ii.  502. 
sac  of,  ii.  502. 

Opening,  saphenous,  i.  308,  ii.  591. 

Optic  thalami,  ii,  219,  256. 
commissure,  ii.  209,  244. 


Optic  nerve,  ii.  244,  260,  402,  168. 
tract,  ii.  207,  244. 

Ora  serrata,  ii.  368. 

Orbicular  bone,  ii.  383. 

Orbits,  i.  159. 

muscles  of,  i.  346. 
nerves  passing  into,  ii.  261. 
number  of  bones  in,  i.  160. 

Organ  of  Rosenmiiller,  ii.  567. 

Organon  adamantinse,  ii.  422. 

Organs  of  circulation,  i.  468. 
deglutition,  ii.  404. 
digestion,  ii.  404. 

proper,  ii.  443. 
generative,  female,  ii.  554. 
male,  ii.  526. 
development  of,  ii.  570. 
mastication,  ii.  404. 
respiration,  ii.  105. 
senses,  ii.  358. 
urine,  ii.  506. 

development  of,  ii.  567. 
voice,  i.  23. 

Osmazome,  i.  47. 

Os  orbiculare  seu  lenticulare,  ii.  383. 
planum,  i.  136. 
tincae,  ii.  560. 

uteri,  externum  et  internum,  ii.  560. 

Ossa  triquetra,  i.  138,  117. 

Wormiana,  i.  138, 

Ossicula  auditus,  ii.  381. 

Ossification,  in  general,  i.  83. 
of  cartilages,  i.  248. 
centres  of,  (see  also  each  Bone,)  i.  94. 
intra-membranous,  i.  83. 
intra-cartilaginous,  i.  85. 
periods  of,  i.  94,  see  also  each  Bone, 
sub-periosteal,  i.  92. 

Osteo-dentine,  ii.  417. 

Ostium  abdominale,  of  fallopian  tube,  ii.  566. 
uterinum,  ii.  566. 

Otic  ganglion,  ii.  277. 

Otoliihes  vel  otoconia,  ii.  392. 

^ Ovaries,  ii.  564. 

development  of,  ii.  567, 

Graafian  vesicles  of,  ii.  565. 
ligaments  of,  ii.  564. 
structure  of,  ii.  584. 
vessels  and  nerves,  ii.  566. 

Ovicapsule,  ii.  565. 

Ovula  of  Naboth,  ii.  562. 

Ovum,  ii.  565. 

development  of,  ii.  571. 

Pacinian  bodies,  ii.  170. 

end  of  nerve-fibre  in,  ii.  172. 
function  of  ii.  173. 
structure  of,  ii.  171. 
vessels  of.  ii.  172. 

Palate,  ii.  434. 

arches  of,  ii.  435. 
hard,  ii.  434. 
soft,  ii.  435. 

muscles  of,  ii.  436. 

Palpebrffi,  ii.  358. 

Palpebral  cartilages,  ii.  359. 
muscles,  ii.  358. 

Pampiniform  plexus,  ii.  553. 

Pancreas,  ii.  493. 

development  of,  ii.  496. 
duct  of  h.  495. 
fluid  of,  ii.  406. 


INDEX. 


632 


Pancreas,  lesser,  ii.  494. 
struciure  ol,  ii.  494. 
vessels  and  nerves  of,  ii.  496. 
weight  ol,  ii.  494. 

Pancreatic  duct,  ii.  495. 
juice,  ii.  495. 

Panniculus  adiposus,  ii.  71,  85. 

Papilla  lacrynialis,  ii.  359. 

PapilltE,  conjunctival,  ii.  87. 
cutaneous,  ii.  87. 
dental,  ii.  418. 
mucous,  ii.  81. 
conicte,  li.  81,  431. 
filiforines,  ii.  431. 
fungiformes,  ii.  431. 
cesophageal,  ii.  443. 
vallatiE,  ii.  430. 
of  kidney,  ii.  508. 

Par  trigeminum,  ii.  245,  263. 
vagum,  li.  247,  285,  288. 

Parenchyma  of  glands,  ii.  103. 
of  kidney,  it.  514. 

Parenchymal  tissue,  i.  227. 

Parotid  gland,  ii.  437. 

Pars  intermedia  of  vestibule,  ii.  557. 

Patella,  i.  1 12. 

Pecten,  i.  144. 

Pectiniform  septum,  ii.  530. 

Peculiarities  of  arteries,  see  each  Artery. 

Peduncles  of  cerebellum,  ii.  224. 
cerebrum,  ii.  211. 
corpus  callosum,  ii.  210. 
pineal  gland,  ii.  223. 

Pelvis,  i.  205. 

articulations  of,  i.  274. 
axis  of,  i.  207. 
brim  and  outlet  of,  i.  205. 
dimensions  of,  i.  208. 
inclination  of,  i.  205. 
of  kidney,  ii.  509,  516. 

Penis,  ii.  528. 

corpus  cavernosum,  ii.  529. 

spongiosum,  ii.  533. 
development  of,  ii.  573. 
glans  of,  ii.  528. 
helicine  arteries  of,  ii.  532. 
ligament,  suspensory  of,  ii.  529. 
muscles  of,  ii.  537. 
nerves  and  lymphatics  of,  ii.  534. 
vessels  of,  ii.  531. 

Penniform  muscles,  i.  315. 

Perforated  space,  anterior,  ii.  210. 
posterior,  ii.  208. 

Pericardium,  i.  469. 

Perichondrium,  i.  238. 

Perilymph,  of  labyrinth,  ii.  391. 

PerintEum,  ii.  598. 

development  of,  ii.  573. 
muscles  of,  ii.  600. 

Periodontal  membrane,  ii.  405. 

Periosteum,  i.  80. 
of  teeth,  ii.  405. 

Peristaltic  action,  i.  329. 

Peritonseum,  ii.  500. 

continuity  of,  traced,  ii.  503. 
folds  of,  ii.  501. 
fossa3  or  pouches  of,  ii.  502. 
ligaments  of,  ii.  501. 
mesenteries  of,  ii.  502. 
omenta  of,  ii.  501. 
structure  of,  ii.  500. 
vessels  and  nerves,  ii.  505. 


Pes  anserinus,  ii.  279. 
accessorius,  ii.  217. 
hippocampi,  ii.  217. 

Petrous  bone,  i.  125. 

Pia  mater,  ii.  250. 
of  cord,  ii.  250. 

Pigment  cells,  i.  64,  ii.  69. 

Pigmenturn,  ii.  72. 
of  eye,  ii.  69,  364. 

Pillars  of  fauces,  ii.  436. 
fornix,  ii.  216. 
diaphragm,  i.  422. 

Pineal  gland,  ii.  222. 

Pinna,  ii.  373. 

muscles  of,  ii.  375. 

Pituitary  body,  ii.  209. 
membrane,  ii.  399. 

Phalanges  of  fingers,  i.  194,  197. 
toes,  i.  222,  226. 

Pharynx,  ii.  440. 

muscles  of,  ii.  441. 
action  of,  ii.  441. 

Plasma  of  chyle,  ii.  36. 
lymph,  ii,  34. 
blood,  i.  499. 

Pleura  costalis,  ii.  109. 

of  mediastinum,  ii.  109. 
pulmonalis,  ii.  109. 

Pleurae,  ii.  109. 

structure  of,  ii.  110. 

Plexuses  of  nerves,  ii.  165. 
aortic,  ii.  353. 

inferior,  ii.  353. 
brachial,  ii.  306. 

branches  of,  ii.  306. 
cardiac,  ii.  348. 
carotid,  ii.  343.  • 
cervical,  ii.  302. 

posterior,  ii.  299. 
coeliac,  ii.  352. 
coronary,  anterior,  ii.  349. 
posterior,  ii.  350. 
of  the  stomach,  ii.  352. 
hepatic,  ii.  352. 
hypogastric,  ii.  354. 

inferior,  ii.  354. 
lumbar,  ii.  321. 

branches  of,  ii.  321. 
mesenteric,  inferior,  ii.  353. 

superior,  ii.  352. 
cesophageal,  ii.  291. 
pharyngeal,  ii,  285,  341. 
phrenic,  ii.  351. 

pulmonary,  anterior,  ii.  291,  349. 

posterior,  ii.  291,  288. 
renal,  ii.  351. 
sacral,  ii.  330. 
solar,  ii.  350. 
spermatic,  ii.  351. 
patellar,  ii.  328. 
prevertebral,  ii.  340. 
cavernous,  ii.  344. 
epigastric,  ii.  350. 
diaphragmatic,  ii.  351. 
supra-renal,  ii.  351. 
pancreatic,  ii.  352. 
haemorrhoidal,  inferior,  ii.  354. 

superior,  ii.  354. 
prostatic,  ii.  355. 
splenic,  ii.  352. 
tonsillar,  ii.  285. 
vertebral,  ii.  345. 


INDEX. 


633 


Plexus,  cardiac,  superficial,  ii.  349. 
deep,  ii.  349. 
gangliosus,  ii.  354. 
infraorbital,  ii.  270. 
inter-mesenteric,  ii.  352. 

^ ovarian,  ii.  355. 
pelvic,  ii.  354. 
tympanic,  ii.  386. 
vesical,  ii.  355. 
of  lymphatics,  ii.  38. 
of  veins,  i.  517. 
choroid,  ii.  214,  219. 

minor,  ii.  228. 
ovarian,  ii.  29,  566. 
pampiniform,  ii.  29,  553,  566. 
pterygoid,  ii.  9. 
prostatic,  ii.  527. 
spermatic,  ii.  29,  553. 
uterine,  ii.  563. 

Plica  centralis  retinae,  ii.  369. 
semi-lunaris,  ii.  360. 

Plicae  semi-lunares,  ii.  521,  562. 

Pomum  Adami,  ii.  125. 

Pons  Varolii,  ii.  196,  201,  225. 
internal  structure  of,  ii.  234. 
weight  of,  ii.  189. 

Popliteal  space,  i.  628. 

Pores  of  skin,  ii.  94. 

Porta  or  portal  fissure,  ii.  477. 

Portal  canals,  ii.  481. 
circulation,  i.  512. 
vein,  ii.  31. 

Portio  dura,  nerve,  ii.  246,  279. 

mollis,  nerve,  ii.  393,  278,  282. 

Pouches,  laryngeal,  ii.  132. 

Poupart’s  ligament,  i.  277,  ii.  578. 

Preformative  membrane,  ii.  421. 

Prepuce,  ii.  528. 

Primitive  band  or  axis  of  nerve-fibre,  ii.  150. 

Process,  acromion,  i.  176. 
basilar,  i.  116. 
clinoid,  i.  129,  131. 
cochleariform,  i.  127,  ii.  380. 
coracoid,  i.  177. 
coronoid,  i.  149. 
hamular,  i.  131. 
of  helix,  ii.  375. 
mastoid,  i.  125. 
pterygoid,  i.  131. 
sphenoidal,  i.  147. 
styloid,  i.  126. 
vaginal,  i.  126. 
vermiform,  ii.  225. 
inferior,  ii.  226. 

Processes  of  bones,  i.  72. 
ciliary  (eye),  ii.  365,  371. 

Processus  a cerebello  ad  medullam,  ii.  224. 
pontem,  ii.  224. 
testes,  ii.  224,  237. 
arciformes,  ii.  201. 
gracilis  (of  malleus),  ii.  382. 
vaginalis  peritontei,  ii.  543,  572. 
remains  of,  ii.  343. 

Promontory  of  tympanum,  ii.  379. 

Prostate  gland,  ii.  525. 

development  of,  ii.  573. 
levator  muscle  of,  ii.  472. 
surgical  anatomy  of,  ii.  601. 

Prostatic  portion  of  urethra,  ii.  534. 
development,  ii.  573. 
sinus,  ii.  535. 

Protein,  i.  44. 

compounds,  i.  43. 


Pudendum,  ii.  554. 

Puncta  lacrymalia,  ii.  360. 

Pupil  of  eye,  ii.  366. 

Pylorus,  ii.  452. 

Pyramid,  in  tympanum,  ii.  380. 
of  cerebellum,  ii.  226. 

Pyramids,  anterior,  ii.  197,  232. 
posterior,  ii.  200,  231. 
of  kidney,  ii.  508. 
of  Ferrein,  ii.  510. 
of  Malpighi,  ii.  508. 

Quadrigeminal  bodies,  ii.  223. 

Racemose  glands,  ii.  101. 

Raphe  of  perinaeum,  ii.  540,  573. 

Receptaculum  chyli,  ii.  46. 

Recto-uterine  folds,  ii.  562. 
vesical  cul-de-sac,  ii.  520. 
folds,  ii.  521. 

Rectum,  ii.  467.  (See  Intestine,  large.) 
structure  of,  ii.  468. 
surgical  anatomy  of,  ii.  602. 

Regeneration  of  bone,  i.  94. 
cartilage,  i.  243. 
cellular  tissue,  i.  232. 
fibrous  tissue,  i.  235. 
hair,  ii.  92. 

mucous  membranes,  ii.  83. 

muscular  tissue,  i.  324. 

nails,  ii.  89. 

nerves,  ii.  184. 

serous  membranes,  ii.  77. 

skin,  ii.  96. 

textures,  i.  71. 

Renes  succenturiati,  ii.  514. 

Reservoirs  of  glands,  ii.  104. 

Restiform  bodies,  ii.  199,  231,  235. 

Rete  mirabile,  i.  513. 
mucosum,  ii.  70,  85. 
vasculosum  testis,  ii.  548. 

Reticular  tissue,  i.  227. 

Reticulated  white  substance,  ii.  205. 

Retina,  ii.  368. 

Retro-peritoneal  membrane,  ii.  500. 

Rigor  mortis,  i.  330. 

Rima  glottidis,  ii.  132. 

Ring,  abdominal,  external,  ii.  579. 
internal,  i.  303,  ii.  582. 
femoral,  ii.  594. 

Roots  of  nerves,  cranial,  ii.  243,  248. 
spinal,  ii.  192,  229,  295. 

Rugae  of  mucous  membrane,  ii.  79. 

Sac,  lacrymal,  ii.  361. 
of  omentum,  ii.  502. 

Sacculus  vestibuli,  ii.  391. 

Sacrum,  i.  96,  103,  113. 

Saliva,  ii.  439. 

Salivary  glands,  ii.  437. 
development  of,  ii.  440. 

Saphenous  nerves,  ii.  327,  334. 
opening,  i.  308,  592. 
veins,  ii.  25. 

Sarcolemma,  i.  316. 

Sarcous  elements,  i.  318. 

Satellite  veins,  i.  517. 

Scala  tympani,  ii.  390. 
vestibuli,  ii.  390. 

Scalae  of  cochlea,  ii.  390. 

Scarf-skin,  ii.  84. 

Schindylesis,  i.  248. 

Schneiderian  membrane,  ii.  399. 


634 

Sclerotic,  ii.  3G3. 

Scrobiculus  cordis,  ii.  445. 

Scrotum,  ii.  540. 

development  of,  ii.  572. 

Sebaceous  glands,  ii.  93. 

Secreting  apparatus,  ii.  98. 
cells,  ii.  98. 
fringes,  ii.  100. 
glands,  ii.  97. 
membrane,  ii.  99. 
surfaces,  ii.  100. 

increase  of,  ii.  100. 

Secretion,  ii.  97. 

cell-agency  in,  ii.  98. 
conditions  of,  ii.  99. 
nutritive,  ii.  97. 
reservoirs  of,  ii.  104. 
source  of,  ii.  98. 

Sella  Turcica,  i.  129. 

Semen,  ii.  553. 

Semicircular  canals,  ii.  388. 
membranous,  ii.  392. 

Seminal  animalcules,  ii.  553. 
ducts,  ii.  552. 
vesicles,  ii.  551. 

Seminiferous  tubes,  ii.  547. 

Semipenniform  muscles,  i.  315. 

Senses,  organs  of,  ii.  353. 

Sensibility,  i.  50. 

Septa,  intermuscular,  i,  293. 

Septula  renum,  ii.  508. 

Septum  of  auditory  ampullae,  ii.  392. 
crurale,  ii.  594. 
of  heart,  auricular,  i.  474. 
development  of,  i.  489. 
ventricular,  i.  475. 
lucidum,  ii.  214,  215. 
of  medulla  oblongata  and  pons,  ii.  234. 
of  nares,  i.  162,  ii.  396. 
of  nose,  cartilaginous,  ii.  396. 

osseous,  i.  162. 
pectiniforme,  ii.  530. 
scroti,  ii.  541. 
subarachnoid,  ii.  252. 
of  tongue,  ti.  434. 

Serous  membranes,  ii.  75. 
arrangement  of,  ii.  75. 
fluid  of,  ii.  76. 
folds  of,  ii.  75. 
inflammation  of,  ii.  77. 
reparation  of,  ii.  77. 
structure  of,  ii.  76. 
vessels  and  nerves  of,  ii.  76. 

Serous  vessels,  i.  524. 

Serum,  i.  495,  505. 

Sheath  of  muscles,  i.  314. 
femoral,  i.  592. 
of  rectus  muscle,  i.  418. 

Sheaths  of  tendons,  i.  186,  246. 

Sigmoid  cavity,  humerus,  i.  183. 
ulna,  i.  188. 

notch,  lower  jaw,  i.  150. 
flexure  of  colon,  ii.  467. 
valves,  pulmonary,  i.  477. 
aortic,  i.  481. 

Sinus,  basilar,  ii.  24. 
cavernous,  ii.  23. 

nerves  near,  ii.  261. 
circular,  ii.  23. 

of  iris,  ii.  367. 
of  jugular  vein,  ii.  10. 

kidney,  ii.  508. 
lateral,  ii.  22. 


INDEX. 

Siuus,  longitudinal,  inferior,  i.  22. 
superior,  i.  22. 
occipital,  anterior,  ii.  24. 

posterior,  ii.  23. 
petrosal,  inferior,  ii.  24. 

superior,  ii.  23. 
of  portal  vein,  ii.  31. 
pocularis,  ii.  535,  573. 
prostatic,  ii.  535. 
straight,  ii.  22. 
transverse,  ii.  24. 
uro-genitalis,  ii.  569,  573. 
venosus,  left,  ii.  478. 

right,  ii.  473. 
of  vestibule,  ii.  391. 

Sinuses,  aortic,  i.  482,  527. 
ethmoidal,  i.  137,  400. 
frontal,  i.  122,  162, 
of  larynx,  ii.  132. 
mastoid  (cells),  ii.  378. 
maxillary,  i.  140,  162. 
sphenoidal,  i.  130,  162. 
of  Valsalva,  aortic,  i.  482,  527. 

pulmonary,  i.  482. 

(venous)  of  cranium,  ii.  21,  49. 
confluence  of,  ii.  22. 

Skeleton,  i.  95. 

connexions  of,  i.  247. 
human,  distinctions  of,  i.  168. 

Skin,  ii.  84. 

basement  membrane  of,  ii.  86. 
colour  of,  ii.  85. 
corium  of,  ii.  88. 

chemical  nature  of,  ii.  88. 
cuticle,  ii.  84. 

chemical  nature  of,  ii.  85. 
cutis  vera  or  corium,  ii.  85. 
derma  or  corium,  ii.  85. 
epidermis  or  cuticle,  ii.  84. 
functions  of,  ii.  95. 
furrows  of,  ii.  86. 
glands,  sebaceous,  ii.  93. 

sudoriferous,  ii.  93. 
nails  and  hairs  of,  ii.  88. 
nerves  of,  ii.  88. 
papillae  of,  ii.  87. 
pigmentum  of,  ii.  79. 
pores  of,  ii.  94. 
reproduction  of,  ii.  96. 
rete  mucosum  of,  ii.  85. 
true,  ii.  85. 
vessels  of,  ii.  87. 
vital  properties  of,  ii.  95. 

Skull,  base  of,  i.  154,  158. 
bones  of,  i.  115. 

analogy  with  vertebrae,  i.  It 
connexion  of,  i.  152. 
external  surface,  i.  154. 
front  of,  i.  156. 

general  conformation  of,  i.  154. 
internal  surface,  i.  158. 

fossae  of,  i.  158. 
sides  of,  i.  157. 

Smegma  praeputii,  ii.  529. 

Spermatic  cord,  ii.  540. 
coverings  of,  ii.  540. 
fascia,  ii.  541,  579. 
vessels,  ii.  552. 

Spermatozoa,  ii.  553. 

Spinal  cord,  general  anatomy  of,  ii. 
central  canal  of,  ii.  195. 
columns  of,  ii.  113,  229. 
their  course,  ii.  731. 


INDEX. 


635 


Spinal  cord,  commissures  of,  ii.  193. 
fissures  of,  ii.  192. 
internal  structure  of,  ii.  229. 
ligament  of,  ii.  491. 
or  marrow,  ii.  195. 
membranes  of,  ii.  247. 
sections  of,  ii.  193. 
weight  of,  ii.  190. 

Spinal  nerves,  ii.  290. 

divisions  of,  anterior,  ii.  301. 

posterior,  ii.  297. 
ganglia  of,  ii.  295. 
roots  of,  ii.  191,  229,  295. 

General  Anatomy  of,  see  Nerves,  general 
anatomy  of. 

Spleen,  ii.  496. 

absorbents  of,  ii.  500. 
accessory,  ii.  500. 
capillaries  of,  ii.  499. 
coats  of,  ii.  497. 
corpuscles  of,  ii.  499. 
development  of,  ii.  500. 
hilus  or  fissure  of,  ii.  496. 
ligaments  of,  ii,  497. 
nerves  of,  ii.  500. 
size  and  weight  of,  ii.  497. 
structure  of,  ii.  495. 
substance  of,  ii.  499. 
trabeculte  of,  ii.  498. 
vessels  of,  ii.  498. 
uses  of,  ii.  500. 

Splenculi,  ii.  500. 

Spongy  portion  of  urethra,  ii.  536. 

Stapes,  ii.  383. 

Stearin,  i.  47. 

Stellulae  of  Verheyen,  ii.  513. 

Stenonian  duct,  ii.  438.  , 

Stomach,  ii.  446. 
alveoli  of,  ii.  450. 
capillaries  of,  ii.  452. 
coats  of,  ii.  448. 
development  of,  ii.  473. 
follicles  of,  ii.  452. 
glands  of,  ii.  451. 
mucous  membrane  of,  ii.  449. 
structure  of,  ii.  448. 
tubuli  of,  ii.  451. 
vessels  and  nerves  of,  ii.  452. 
villi  of,  ii.  450. 

Stria  cornea,  ii.  220. 

Striae  longitudinales,  ii.  212,  240. 
of  muscular  fibre,  i.  315. 

Subcutaneous  tissue,  ii.  85. 

Submucous  tissue,  i.  227. 

Subarachnoid  space,  ii.  251. 
septum,  ii.  252. 

Sublingual  gland,  ii.  439. 

Submaxillary  gland,  ii.  438. 

Subpeduncular  lobe,  cerebellum,  ii.  226. 

Subperitonteal  membrane,  ii.  501. 

Sudoriferous  glands,  ii.  94. 

Subserous  cellular  tissue,  i.  75. 
tissue,  i.  227. 

Substantia  cinerea  gelatinosa,  ii.  155,  194. 
spongiosa,  ii.  156. 

Sulci  (brain),  ii.  202,  203. 

(heart),  i.  472. 

Supercilia,  ii.  358. 

Superciliary  ridges,  i.  120. 

Supplementary  organs,  see  those  organs. 

Supra-renal  capsules,  ii.  514. 
development  of,  ii.  568. 

Surgical  anatomy  of  arteries,  brachial,  i.  580. 


Surgical  anatomy  of  arteries,  carotid,  i.  538. 
iliac,  common,  i.  607. 
external,  i.  618. 
internal,  i.  609. 
epigastric,  ii.  582. 
femoral,  i.  625. 
subclavian,  i.  561. 
ischio-rectal  fossae,  ii.  598,  604. 
hernia,  femoral,  ii.  591. 

inguinal,  ii.  578. 
perinaeum,  ii.  598. 

Sutures,  of  cranium  and  face,  i.  152. 

Sweat  glands,  ii.  94. 

Sylvian  aqueduct,  ii.  222,  227. 
fissure,  ii.  257. 

convolution  of,  ii.  203. 
ventricle,  ii.  215. 

Sympathetic  plexuses,  ii.  348.  See  Plexuses, 
nerves,  ii.  175,  339. 

cord  of,  in  neck,  ii.  341. 
loins,  ii.  347. 
pelvis,  ii.  348. 
thorax,  ii.  345. 
cranial  branches,  ii.  343. 
ganglia  of,  ii.  341. 
prevertebral  part  of,  ii.  348. 
vascular  branches  of,  ii.  342. 
general  anatomy  of.  See  Nerve,  gen- 
eral anatomy  of. 

Symphysis  menti,  i.  149. 
pubis,  i.  201,  205. 
sacfo-iliac,  i.  275. 

Synarthrosis,  i.  247. 

Synchondrosis,  sacro-iliac,  i.  275. 

Synovia,  i.  246. 

Synovial  bursts,  i.  246. 
capsules,  i.  245. 
folds  or  fringes,  i.  245. 
membranes,  i.  244. 
articular,  i.  245. 
bursal,  i.  246. 
fluid  of,  i.  246. 
structure  of,  i.  244. 
vaginal,  i.  246. 
sheaths,  i.  246. 

Tanno-gelatin,  i.  46. 

Taenia  semicircularis,  ii.  214,  220. 
hippocampi,  ii.  217. 

Tapetum,  ii.  364. 

Tarsal  ligament,  of  eyelid,  ii.  359. 
ligaments,  foot,  i.  288. 

Tarsi  nr  tarsal  cartilages  (eyelids),  ii.  359. 
tensor  muscle,  i.  337. 

Tarsus,  i.  217,  224. 

Tartar  of  teeth,  ii.  429. 

Teeth,  ii.  405. 

analogy  with  bones,  ii.  428. 
bicuspid,  ii.  408. 
canine,  ii.  407. 
cavity  of,  ii.  410,  419. 
cement  of,  ii.  411,  415. 
characters  of,  general,  ii.  406. 
special,  ii.  406. 

crusta,  petrosa  of,  ii.  411,  415. 
cuspidate,  ii.  407. 
dentine  of,  ii.  410. 
development  of,  ii.  417. 
enamel  of,  ii.  411,  413,  422. 
eruption  of,  ii.  423. 
formation  of,  ii.  420. 
growth  of,  ii.  423. 
incisor,  ii.  406. 


636 


INDEX. 


Teeth,  intcrtubular  substance  of,  ii.  413. 
ivory  of,  ii.  410. 

formation  of,  ii.  424. 
milk,  ii.  405,  409. 
molar,  ii.  408. 
multicuspidate,  ii.  408. 
nerves  of,  ii.  173,  410. 
permanent,  ii.  405. 

development  of,  ii.  424. 
eruption  of,  ii.  427,  423. 
pulps  of,  ii.  410. 

formation  of,  ii.  419. 
sacs  of,  ii.  419,  424. 
structure  of,  ii.  410. 
supernumerary,  ii.  405. 
tartar  of,  ii.  429. 
temporary,  ii.  405,  409. 
development  of,  ii.  417. 
eruption  of,  ii.  423. 
shedding  of,  ii.  427. 
vessels  of,  ii.  403,  428. 
wisdom,  ii.  408. 

Tegmentum,  ii.  237. 

Tela  choroidea,  ii.  219. 

Tendon  of  Achilles,  i.  451. 

cordiform  or  central  of  diaphragm,  i.  424. 
conjoined,  i.  417,  ii.  581. 

(straight)  of  eyelids,  ii.  359. 

Tendons,  i.  233. 

connexion  with  muscles,  i.  319. 

Tentorium,  ii.  249. 

Testes,  ii.  545. 

coni  vasculosi  of,  ii.  549. 
coverings  of,  ii.  540. 

vessels  and  nerves  of,  ii.  544. 
descent  of,  ii.  543,  572. 
development  of,  ii.  570. 
epididymis  of,  ii.  545. 
excretory  duct  of,  ii.  549. 
lobes  of,  ii,  547. 
mediastinum  of,  ii.  546. 
rete  vasculosum  of,  ii.  548. 
spermatic  cord  of,  ii.  540. 
structure  of,  ii.  546. 
tubuli  of,  ii.  547. 
tubuli  recti  of,  ii.  548. 
tunica  albuginea  of,  ii.  546. 
vaginalis  of,  ii.  544. 
vasculosa  of,  ii.  547. 
vas  aberrans  of,  ii.  551. 

deferens  of,  ii.  549. 
vasa  eff'erentia  of,  ii.  548. 

recta  of,  ii,  548. 
vessels  and  nerves  of,  ii.  552. 

(cerebrum),  ii.  224. 

Textures  in  general,  i.  39. 

chemical  composition  of,  i.  42. 

" ultimate,  i.  42. 

proximate,  i.  42. 
development  of,  i.  51. 

vegetable  i.  52. 
animal,  i.  54. 
elements  of,  i.  42. 
enumeration  of,  i.  39. 
nutrition  of,  i.  68. 
particular,  see  Tissue,  &c. 
permeability  of,  i.  41. 
physical  properties  of,  i.  40. 
regeneration  of,  i.  71. 
systems  of,  i.  39. 
vital  properties  of,  i.  49. 

Thalami  optici,  ii.  214,  220. 

I'heca  vertebralis,  ii.  248. 


Thoracic  duct,  ii.  46. 

Thorax,  bones  of,  i.  164. 
contents  of,  i.  469. 
general  description  of,  i.  468. 

Thymus  gland,  ii.  142. 
development  of,  ii.  145. 
structure  of,  ii.  143. 
vessels  and  nerves  of,  ii.  144. 

Thyroid  axis,  i.  567. 

body  or  gland,  ii.  140,  142. 
development  of,  ii.  142. 
levator  muscle  of,  ii.  141. 
structure  of,  ii.  141. 
vessels  and  nerves  of,  ii.  142. 
cartilage,  ii.  124. 

Tissue,  adipose,  ii.  71. 
areolar,  i.  227. 
cartilaginous,  i.  237. 
cellular,  i.  227. 
cuticular,  ii.  59. 
epidermic,  ii.  59. 
epithelial,  ii.  59. 
fibrous,  i.  232. 
filamentous,  i.  227. 
muscular,  i.  313. 

involuntary,  i.  313. 
voluntary,  i.  313. 
nervous,  ii.  148. 
reticular,  i.  227. 

Tomentum  cerebri,  ii.  250. 

Tongue,  ii.  429. 

mucous  membrane  of,  ii.  432. 
muscles  of,  ii.  433. 
nerves  of,  ii.  434. 
papillae  of  ii.  430. 
septum  of,  ii.  434. 
vessels  of  ii.  434. 

Tonicity  of  arteries,  i.  516. 
muscular,  i.  328. 

Tonsils,  ii.  436. 

Torcular  Herophili,  i.  22. 

Trabeculae  of  corpus  cavernosum,  ii.  531. 
spleen,  ii.  498. 

Trabs  cerebri,  ii.  211. 

Trachea,  ii.  105. 

cartilages  of  ii.  106. 
development  of,  ii.  122. 
glands  of,  ii.  108. 
mucous  coat  of,  ii.  108. 
structure  of,  ii.  106. 
vessels  and  nerves  of,  ii.  108. 

Tractus  opticus,  ii.  207,  244. 

spiralis  foraminulentus,  ii.  395. 

Tragus,  ii.  374. 

muscles  of,  ii.  375. 

Triangle,  of  Hesselbach,  ii.  587. 

Triangular  ligament  of  urethra,  i.  305,  ii.  601. 

Trigone  of  bladder,  ii.  522. 

Trochanters,  i.  210. 

Trochlea,  i.  249. 

Tuba  Eustachiana,  ii.  380. 

Tubae  Fallopianae,  ii.  505. 

Tuber  annulare,  ii.  201. 
cinereum,  ii.  209,  256. 
cochleae,  ii.  379. 
ischii,  i.  202. 

Tubercle,  gray  of  Rolando,  i.  118. 
laminated,  ii.  226. 
of  Lower,  i.  474. 

Tubercula  quadrigemina,  ii.  223. 

Tuberculo  cinereo,  ii.  232. 

Tubular  nerve-fibres,  ii.  149. 

Tubules  of  nervous  substance,  ii.  149. 


INDEX. 


637 


Tubules  of  mucous  membrane,  ii.  82. 

Tubuli  of  Ferrein,  ii.  510. 

uriniferi,  convoluted,  ii.  510. 
ends  of,  ii.  510. 
straight,  ii.  510. 

structure  of,  ii.  510. 
of  large  intestine,  ii.  463. 
recti,  ii.  548. 
seminiferi,  ii.  547. 
of  small  intestine,  ii.  451. 
stomach,  ii.  450. 
teeth,  ii.  412. 
uterus,  ii.  563. 

Tunica,  adiposa  of  kidney,  ii.  507. 
albuginea,  ii.  546. 

of  ovary,  ii.  564. 
erythroides,  ii.  541. 

Ruyschiana,  ii.  364. 
vaginalis,  ii.  544,  572. 
vasculosa  testis,  ii.  547. 
vasculosa  (eye),  ii.  364. 

Tutamina  oculi,  ii.  358. 

Tympanum,  or  middle  ear,  ii.  377. 
bones  or  ossicula  of,  ii.  382. 
cavity  of,  ii.  378. 
ligaments  of,  ii.  383. 
membrand  of,  ii.  380. 

lining,  ii.  385. 
muscles  of,  ii.  383'. 
scala  of,  ii.  390. 

secondary  membrane  of,  ii.  380. 
vessels  and  nerves  of,  ii.  385. 

Umbilicus,  i.  419. 

Urachus,  ii.  519. 

formation  of,  ii.  569. 

Ureters,  ii.  509,  516. 

development  of,  ii.  568. 
muscles  of,  ii.  523. 
structure  of,  ii.  517. 
varieties  of,  ii.  517. 

Urethra,  development  of,  ii.  573. 
female,  ii.  524. 

compressor  muscle  of,  ii.  525,  539. 
orifice  of,  ii.  524,  555. 
male,  ii.  534. 

bulb  of,  ii.  533. 
compressor  of,  ii.  538. 
crest  of,  ii.  534. 
dilatations  of,  ii.  535. 
fossa  navicularis  of,  ii.  535. 
lacunae  of,  ii.  537. 
mucous  membrane  of,  ii.  536. 
muscles  of,  ii.  537. 
orifice  of,  ii.  536. 
portion  of,  membranous,  ii.  535. 
bulbous,  ii.  536. 
prostatic,  ii.  534. 
spongy,  ii.  536. 

Urinary,  bladder.  {See  Bladder,)  ii.  517. 
organs,  ii.  506. 

development  of,  ii.  567. 

Urine,  ii.  514. 

Uterus,  ii.  559. 

arbor  vitae  of,  ii.  561. 
bifid,  ii.  573. 
cavity  of,  ii.  560. 
cellular  tissue  of,  ii.  562. 
cervix,  or  neck,  ii.  560. 
changes  in,  ii.  563. 
coat  of,  mucous,  ii.  561. 

serous,  ii.  561. 
development  of,  ii.  567. 

VOL.  U. 


Uterus,  fibres  of,  ii.  561. 
fundus  of,  ii.  560,  573. 
gravid,  ii.  563. 

nerves  of,  ii.  564. 
ligaments  of,  broad,  ii.  562. 
ovarian,  ii.  563. 
round,  ii.  563,  572. 
nerves  of,  ii.  563. 
os  or  mouth  of,  external,  ii.  560. 
internal,  ii.  560. 
os  tineas  of,  ii.  561. 
tissue,  proper  of,  ii.  561. 
tubular  glands  of,  ii.  563. 
vessels  of,  ii.  563. 
virgin,  ii.  560. 

Utriculus  vestibuli,  ii.  391. 
virilis,  ii.  535,  573. 

Uvea,  ii.  366. 

Uvula,  bladder,  ii.  522. 
cerebellum,  ii.  226. 
throat,  ii.  435. 

muscle  of,  i.  365. 

Vagina,  ii.  557. 

columns  of,  ii.  558. 
development  of,  ii.  573. 
sphincter  of,  ii.  558. 

Vallecula,  ii.  225. 

Valve,  of  Bauhin,  ii.  193. 
cystic  duct,  ii.  490. 

Eustachian,  i.  475,  491,  492. 
ileo-caecal,  or  ilio-coelic,  ii.  465. 
mitral,  or  bicuspid,  i.  480. 

Thebesian,  i.  475. 
tricuspid,  i.  476. 
of  Vieussens,  ii.  224,  226. 

Valves,  auriculo-ventricular,  left,  i.  480. 
right,  i.  476. 
of  Kerkring,  ii.  79,  455. 
lymphatics,  ii.  40. 

sigmoid,  or  semilunar,  aortic,  i.  481. 

pulmonary,  i.  476,  477. 
small  intestine,  ii.  455. 
veins,  i.  519. 

Valvula  Thebesii,  ii.  32. 

Valvulee  conniventes,  ii.  79,  455. 

Varicose  nerve-fibres,  ii.  151. 

Varieties  of  vessels  or  organs,  see  those  parts. 

Vas  aberrans,  ii.  551. 
deferens,  ii.  549. 

development  of,  ii.  571. 

Vasa  aberrantia  (arteries),  brachial,  i.  580. 
afferentia,  of  lymphatic  glands,  ii.  41. 
brevia,  arteries,  i.  598. 

veins,  ii.  31. 
chylifera,  ii.  45. 
efferentia,  of  testis,  ii.  548. 

lymphatic  glands,  ii.  41. 
lactea,  ii.  40,  45. 
recta,  of  testis,  ii.  548. 
serosa,  i.  524. 
vasorum,  i.  515,518. 
vorticosa,  ii.  364. 

Vascula  serpentina,  ii.  548. 

Veins,  General  Anatomy  of,  ii.  5. 
anastomoses  of,  li.  5. 
coats  of,  i.  518. 
contractility  of,  i.  519. 
distribution  of,  i.  517. 
plexuses  of,  i.  517. 
satellite,  i.  517. 
structure  of,  i.  518. 
valves  of,  i.  519. 


54 


INDEX. 


638 

Veins,  vessels  and  nerves  of,  i.  518, 
vital  properties  of,  i.  519. 
Descriptive  Anatomy  of,  ii.  5. 
angular,  ii.  36. 
articular,  of  jaw,  ii.  8. 
auricular  anterior,  ii.  8, 
posterior,  ii.  8. 
axillary,  ii.  14. 
azygos,  ii.  17. 

minor,  ii.  17. 
basilic,  ii.  12. 
basi-vertebral,  ii.  19. 
brachial,  ii.  13. 
brachio-cephalic,  ii.  16. 
bronchial,  ii.  18,  120. 
buccal,  ii.  7. 
capsular,  ii.  29. 
cardiac,  ii.  31. 
cava,  inferior,  ii.  25. 

superior,  ii.  16,  28. 
cerebellar,  ii.  21. 
cerebral,  ii.  21. 
cephalic,  ii.  11. 
of  choroid  coat,  eye,  ii.  364. 
comites,  brachial,  ii.  13. 
femoral,  ii.  26. 
interosseous,  ii.  12, 
popliteal,  ii.  26. 
radial,  ii.  313. 
tibial,  ii.  26. 
ulnar,  ii.  12. 
cordis  magna,  ii.  32. 
media,  ii.  32. 
minimae,  ii.  32,  i.  475. 
parvae,  ii.  32. 

coronary  vein,  of  heart,  ii.  32. 

stomach,  ii.  30. 
of  corpus  striatum,  ii.  21,  20. 
of  cranium,  ii.  18,  21. 
dental,  inferior,  ii.  9. 
of  diploe,  ii.  24. 
dorsal,  spinal,  ii.  19. 

of  penis,  ii.  27. 
duodenal,  ii.  30. 
emulgent,  ii.  29. 
epigastric,  superficial,  ii.  25. 
ethmoidal,  ii.  402. 
facial,  ii.  6. 
femoral,  ii.  26. 
frontal,  ii.  7. 
of  Galen,  ii.  21. 
gastric,  ii.  30. 
gastro-epiploic,  ii.  30. 
hepatic,  ii.  31,  481. 
iliac,  external,  ii.  27. 

internal,  ii.  27. 
iliac,  common,  ii.  27. 
innominate,  ii.  16. 
intercostal,  anterior,  ii.  16. 

superior,  ii.  15. 
interlobular,  ii.  481,  483. 
interosseous,  of  forearm,  ii.  13. 
intra-lobular,  ii.  483,  481. 
jugular,  anterior,  ii.  9. 
external,  ii.  9. 
internal,  ii.  6. 
laryngeal,  ii.  6. 
lingual,  ii.  10. 
of  liver,  ii.  481. 
lumbar,  ii.  28. 
mammary  internal,  ii.  16, 
maxillary  internal,  ii.  9. 
median  cutaneous,  ii.  12. 


Veins,  basilic,  ii.  12. 

cephalic,  ii.  12. 
medulli- spinal,  ii.  19. 
meningeal,  ii.  9. 
mesenteric  inferior,  ii.  30. 

superior,  ii.  30. 
nasal,  ii.  7. 
occipital,  ii.  6. 
ophthalmic,  ii.  24. 
ovarian,  ii.  29. 
palatine,  ii.  8. 
palpebral  inferior,  ii.  7. 
pancreatic,  ii.  30. 
parotid,  ii.  8. 
pharyngeal,  ii.  10, 
phrenic,  ii.  29. 
popliteal,  ii.  26. 
portal,  ii.  29,  31,  481. 
posterior  scapular,  ii.  10. 
pudic  external,  ii.  25. 
pulmonary,  ii..ll4. 
radial  cutaneous,  ii.  11. 

deep,  ii.  13. 
ranine,  ii.  8. 
renal,  ii.  29. 
sacral,  middle,  ii.  28. 
salvatella,  ii.  11. 

saphenous,  long  or  internal,  ii.  25. 

short  or  external,  ii.  25. 
spermatic,  ii.  29,  553. 
spinal,  ii.  18. 
great,  ii.  20. 
posterior,  ii.  20. 
splenic,  ii.  30,  500. 
subclavian,  ii.  14. 
sub-lobular,  ii.  481. 
submental,  ii.  8. 
supra-orbital,  ii.  7. 
supra-renal,  ii.  29. 
supra  scapular,  ii.  10,  14. 
temporal,  deep,  ii.  9. 

middle,  ii.  8. 
temporo-maxillary,  ii.  9. 
thyroid,  superior,  ii.  10. 

middle,  ii.  10. 
thyroid  inferior,  ii.  16. 
transverse  of  face,  ii.  8. 
ulnar-cutaneous  anterior,  ii.  11. 
posterior,  ii.  11. 
deep,  ii.  12. 

umbilical,  i.  493,  ii.  477,  492. 
vaginal,  ii.  558. 

of  liver,  ii.  481. 
vasa  brevia,  ii.  30. 
vertebral,  ii.  15. 
plexuses  of,  ovarian,  ii.  29. 

pampiniform,  ii.  29,  553. 
pterygoid,  ii.  9. 
spermatic,  ii.  29. 

Velum  pendulum  palati,  i.  364,  ii.  435. 
interpositum,  ii.  219. 
medullae  anterius,  ii.  224. 
posterius,  ii.  226. 

Vena  cava,  fossa  of,  ii.  478. 

Vente  comites,  i.  517. 

Ventricle,  of  Arantius,  ii.  200. 

Ventricles  of  brain,  ii.  11,  196. 
fifth,  ii.  215. 
fourth,  ii.  226. 
lateral,  ii.  213. 
third,  ii.  220. 
corpus  callosum,  ii.  211. 
heart.  See  Heart. 


INDEX. 


639 


Ventricles  of  larynx,  ii.  132. 

Ventriculi  tricornes,  ii.  213. 

Vermicular  motion,  i.  329. 

Vermiform  process,  ii.  220. 
inferior,  ii.  226. 

Vertebra  dentata,  i.  102. 
prominens,  i.  102. 

Vertebrse,  i.  96. 

cervical,  i.  98,  101. 
coccygeal,  i.  106. 
cranial,  i.  163. 
dorsal,  i.  99. 
false,  i.  103. 

general  characters  of,  i.  97. 
lumbar,  i.  100,  103. 
ossification  of,  i.  109,  111. 
peculiarities  of,  i.  101. 
sacral,  i.  103. 
true,  i.  97. 

Vertebral  aponeurosis,  i.  298,  373. 
column,  i.  96,  107. 

ligaments  of,  i.  252. 
ossification  of,  i.  109,  114. 

Verumontanum,  ii.  535. 

Vesica  prostatica,  ii.  535. 
fellea,  ii.  489. 
urinaria,  see  Bladder. 

Vesicles  of  glands,  ii.  101. 

Graafian,  ii.  565,  571. 
seminal,  ii.  551,  573. 

Vesico-uterine  folds,  ii.  562. 

Vesiculae  Graafianae,  ii.  565. 
seminales,  ii.  551. 

development,  of,  ii.  573. 
vessels  and  nerves  of,  ii.  553. 

Vessels,  office  of,  i.  510. 

of  different  tissues  and  organs,  see  those 
parts. 

Vestibule,  aqueduct  of,  i.  126,  ii.  387. 
bulbs,  of,  ii.  556. 
of  ear,  ii.  387. 

membranous,  ii.  391. 
nerves  of,  ii.  392,  395. 
saccule  of,  ii.  391. 


Vestibule  of  ear,  scala  of,  ii.  388. 
sinus  of,  ii.  387. 
vessels  of,  ii.  393. 
of  vulva,  ii.  556. 

Vestigium  foraminis  ovalis,  i.  474,  479. 
Vibrios  of  mouth,  ii.  429. 

Vibrissae,  ii.  399. 

Vidian  canal,  i.  132. 

nerve,  ii.  272. 

Villi,  ii.  81. 

of  small  intestine,  ii.  455. 
stomach,  ii.  450. 

Vis  nervosa,  i.  50,  ii.  182. 

Viscera  of  abdomen,  ii.  445. 

position  of,  in  regions,  ii.  505. 
of  thorax,  i.  468. 

Vital  contractility,  i.  49. 

muscular,  i.  325. 
non-muscular,  i.  50,  330. 

Vitreous  humour,  ii.  370. 

Vocal  cords,  i.  482. 

Voluntary  muscles,  i.  313. 

Vortex,  of  heart,  ii.  484. 

Vulva,  ii.  554. 

•development  of,  ii.  573. 
erectile  tissue  of,  ii.  556. 
mucous  membrane  of,  ii.  556. 
vessels  and  nerves  of,  ii.  557. 

Wisdom  tooth,  ii.  408. 

Wolffian  bodies,  ii.  567. 

Womb,  see  Uterus. 

Worm  (cerebellum),  ii.  225. 

Yellow  cartilage,  i.  241. 

fibres  of  cellular  tissue,  i.  229. 
ligaments,  i.  235. 
tissue,  i.  235. 

Zomidin,  i.  47. 

Zonula  lucida,  ii.  371. 

Zinnill  vel  ciliaris,  ii.  371,  366. 
Zygoma,  i.  123. 

Zygomatic  arch,  i.  123,  144. 


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